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Part I. Spring Boot Documentation

This section provides a brief overview of Spring Boot reference documentation. It serves as a map for the rest of the document.

1. About the Documentation

The Spring Boot reference guide is available as

The latest copy is available at docs.spring.io/spring-boot/docs/current/reference .

Copies of this document may be made for your own use and for distribution to others, provided that you do not charge any fee for such copies and further provided that each common questions.

Learn the Spring basics. Spring Boot builds on many other Spring projects. Check the spring.io web-site for a wealth of reference documentation. If you are starting out with Spring, try one of the guides .

Ask a question. We monitor stackoverflow.com for questions tagged with


        spring-boot

Report bugs with Spring Boot at github.com/spring-projects/spring-boot/issues .

	Note
	All of Spring Boot is open source, including the documentation. If you find problems with the docs or if you want to improve them, please get involved .

3. First Steps

If you are getting started with Spring Boot or 'Spring' in general, start with the following topics :

From scratch: Overview | Requirements | Installation
Tutorial: Part 1 | Part 2
Running your example: Part 1 | Part 2

4. Working with Spring Boot

Ready to actually start using Spring Boot? We have you covered :

Build systems: Maven | Gradle | Ant | Starters
Best practices: Code Structure | @Configuration | @EnableAutoConfiguration | Beans and Dependency Injection
Running your code IDE | Packaged | Maven | Gradle
Packaging your app: Production jars
Spring Boot CLI: Using the CLI

5. Learning about Spring Boot Features

Need more details about Spring Boot’s core features? The following content is for you :

Core Features: SpringApplication | External Configuration | Profiles | Logging
Web Applications: MVC | Embedded Containers
Working with data: SQL | NO-SQL
Messaging: Overview | JMS
Testing: Overview | Applications | Utils
Extending: Auto-configuration | @Conditions

6. Moving to Production

When you are ready to push your Spring Boot application to production, we have some tricks that you might like:

Management endpoints: Overview | Customization
Connection options: HTTP | JMX
Monitoring: Metrics | Auditing | Tracing | Process

7. Advanced Topics

Finally, we have a few topics for more advanced users:

Spring Boot Applications Deployment: Cloud Deployment | OS Service
Build tool plugins: Maven | Gradle
Appendix: Application Properties | Auto-configuration classes | Executable Jars

Part II. Getting Started

If you are getting started with Spring Boot, or "Spring" in general, start by reading this section. It answers the basic “what?”, “how?” and “why?” questions. It includes an introduction to Spring Boot, along with installation instructions. We then walk you through building your first Spring Boot application, discussing some core principles as we go.

8. Introducing Spring Boot

Spring Boot makes it easy to create stand-alone, production-grade Spring based Applications that you can run. We take an opinionated view of the Spring platform and third-party libraries, so that you can get started with minimum fuss. Most Spring Boot applications need very little Spring configuration.

You can use Spring Boot to create Java applications that can be started by using java -jar or more traditional war deployments. We also provide a command line tool that runs “spring scripts”.

Our primary goals are:

Provide a radically faster and widely accessible getting started experience for all Spring development.
Be opinionated out of the box but get out of the way quickly as requirements start to diverge from the defaults.
Provide a range of non-functional features that are common to large classes of projects (such as embedded servers, security, metrics, health checks, and externalized configuration).
Absolutely no code generation and no requirement for XML configuration.

9. System Requirements

Spring Boot 2.0.0.M7 requires Java 8 and Spring Framework 5.0.2.RELEASE or above. Explicit build support is provided for Maven 3.2+ and Gradle 4.

9.1 Servlet Containers

The following embedded servlet containers are supported out of the box:

Name	Servlet Version
Tomcat 8.5	3.1
Jetty 9.4	3.1
Undertow 1.3	3.1

You can also deploy Spring Boot applications to any Servlet 3.0+ compatible container.

10. Installing Spring Boot

Spring Boot can be used with “classic” Java development tools or installed as a command line tool. Either way, you need Java SDK v1.8 or higher. Before you begin, you should check your current Java installation by using the following command:

$ java -version

If you are new to Java development or if you want to experiment with Spring Boot, you might want to try the Spring Boot CLI (Command Line Interface) first, otherwise, read on for “classic” installation instructions.

10.1 Installation Instructions for the Java Developer

You can use Spring Boot in the same way as any standard Java library. To do so, include the appropriate spring-boot-*.jar files on your classpath. Spring Boot does not require any special tools integration, so you can use any IDE or text editor. Also, there is nothing special about a Spring Boot application, so you can run and debug a Spring Boot application as you would any other Java program.

Although you could copy Spring Boot jars, we generally recommend that you use a build tool that supports dependency management (such as Maven or Gradle).

10.1.1 Maven Installation

Spring Boot is compatible with Apache Maven 3.2 or above. If you do not already have Maven installed, you can follow the instructions at maven.apache.org .

	Tip
	On many operating systems, Maven can be installed with a package manager. If you use OSX Homebrew, try `brew install maven` . Ubuntu users can run `sudo apt-get install maven` . Windows users with Chocolatey can run `choco install maven` from an elevated (administrator) prompt.

Spring Boot dependencies use the org.springframework.boot groupId . Typically, your Maven POM file inherits from the spring-boot-starter-parent project and declares dependencies to one or more “Starters” . Spring Boot also provides an optional Maven plugin to create executable jars.

The following listing shows a typical pom.xml file:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.example</groupId>
	<artifactId>myproject</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<!-- Inherit defaults from Spring Boot -->
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.0.0.M7</version>
	</parent>
	<!-- Add typical dependencies for a web application -->
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
	</dependencies>
	<!-- Package as an executable jar -->
	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>
	<!-- Add Spring repositories -->
	<!-- (you don't need this if you are using a .RELEASE version) -->
	<repositories>
		<repository>
			<id>spring-snapshots</id>
			<url>http://repo.spring.io/snapshot</url>
			<snapshots><enabled>true</enabled></snapshots>
		</repository>
		<repository>
			<id>spring-milestones</id>
			<url>http://repo.spring.io/milestone</url>
		</repository>
	</repositories>
	<pluginRepositories>
		<pluginRepository>
			<id>spring-snapshots</id>
			<url>http://repo.spring.io/snapshot</url>
		</pluginRepository>
		<pluginRepository>
			<id>spring-milestones</id>
			<url>http://repo.spring.io/milestone</url>
		</pluginRepository>
	</pluginRepositories>
</project>

	Tip
	The `spring-boot-starter-parent` is a great way to use Spring Boot, but it might not be suitable all of the time. Sometimes you may need to inherit from a different parent POM, or you might not like our default settings. In those cases, see Section 13.2.2, “Using Spring Boot without the Parent POM” for an alternative solution that uses an `import` scope.

10.1.2 Gradle Installation

Spring Boot is compatible with Gradle 4. If you do not already have Gradle installed, you can follow the instructions at www.gradle.org/ .

Spring Boot dependencies can be declared by using the org.springframework.boot group . Typically, your project declares dependencies to one or more “Starters” . Spring Boot provides a useful Gradle plugin that can be used to simplify dependency declarations and to create executable jars.

The following example shows a typical build.gradle file:

buildscript {
	repositories {
		jcenter()
		maven { url 'http://repo.spring.io/snapshot' }
		maven { url 'http://repo.spring.io/milestone' }
	dependencies {
		classpath 'org.springframework.boot:spring-boot-gradle-plugin:2.0.0.M7'
apply plugin: 'java'
apply plugin: 'org.springframework.boot'
apply plugin: 'io.spring.dependency-management'
jar {
	baseName = 'myproject'
	version =  '0.0.1-SNAPSHOT'
repositories {
	jcenter()
	maven { url "http://repo.spring.io/snapshot" }
	maven { url "http://repo.spring.io/milestone" }
dependencies {
	compile("org.springframework.boot:spring-boot-starter-web")
	testCompile("org.springframework.boot:spring-boot-starter-test")
}

10.2 Installing the Spring Boot CLI

The Spring Boot CLI (Command Line Interface) is a command line tool that you can use to quickly prototype with Spring. It lets you run Groovy scripts, which means that you have a familiar Java-like syntax without so much boilerplate code.

You do not need to use the CLI to work with Spring Boot, but it is definitely the quickest way to get a Spring application off the ground.

10.2.1 Manual Installation

You can download the Spring CLI distribution from the Spring software repository:

Cutting edge snapshot distributions are also available.

Once downloaded, follow the INSTALL.txt instructions from the unpacked archive. In summary, there is a spring script ( spring.bat for Windows) in a bin/ directory in the .zip file. Alternatively, you can use java -jar with the .jar file (the script helps you to be sure that the classpath is set correctly).

10.2.2 Installation with SDKMAN!

SDKMAN! (The Software Development Kit Manager) can be used for managing multiple versions of various binary SDKs, including Groovy and the Spring Boot CLI. Get SDKMAN! from sdkman.io and install Spring Boot by using the following commands:

$ sdk install springboot
$ spring --version
Spring Boot v2.0.0.M7

If you are developing features for the CLI and want easy access to the version you built, use the following commands:

$ sdk install springboot dev /path/to/spring-boot/spring-boot-cli/target/spring-boot-cli-2.0.0.M7-bin/spring-2.0.0.M7/
$ sdk default springboot dev
$ spring --version
Spring CLI v2.0.0.M7

The preceding instructions install a local instance of spring called the dev instance. It points at your target build location, so every time you rebuild Spring Boot, spring is up-to-date.

You can see it by running the following command:

$ sdk ls springboot
================================================================================
Available Springboot Versions
================================================================================
> + dev
* 2.0.0.M7
================================================================================
+ - local version
* - installed
> - currently in use
================================================================================

10.2.3 OSX Homebrew Installation

If you are on a Mac and use Homebrew , you can install the Spring Boot CLI by using the following commands:

$ brew tap pivotal/tap
$ brew install springboot

Homebrew installs spring to /usr/local/bin .

	Note
	If you do not see the formula, your installation of brew might be out-of-date. In that case, run `brew update` and try again.

10.2.4 MacPorts Installation

If you are on a Mac and use MacPorts , you can install the Spring Boot CLI by using the following command:

$ sudo port install spring-boot-cli

10.2.5 Command-line Completion

The Spring Boot CLI includes scripts that provide command completion for the BASH and zsh shells. You can source the script (also named spring ) in any shell or put it in your personal or system-wide bash completion initialization. On a Debian system, the system-wide scripts are in /shell-completion/bash and all scripts in that directory are executed when a new shell starts. For example, to run the script manually if you have installed using SDKMAN!, use the following commands:

$ . ~/.sdkman/candidates/springboot/current/shell-completion/bash/spring
$ spring <HIT TAB HERE>
  grab  help  jar  run  test  version

	Note
	If you install the Spring Boot CLI by using Homebrew or MacPorts, the command-line completion scripts are automatically registered with your shell.

10.2.6 Quick-start Spring CLI Example

You can use the following web application to test your installation. To start, create a file called app.groovy , as follows:

@RestController
class ThisWillActuallyRun {
	@RequestMapping("/")
	String home() {
		"Hello World!"
}

Then run it from a shell, as follows:

$ spring run app.groovy

	Note
	The first run of your application is slow, as dependencies are downloaded. Subsequent runs are much quicker.

Open localhost:8080 in your favorite web browser. You should see the following output:

Hello World!

10.3 Upgrading from an Earlier Version of Spring Boot

If you are upgrading from an earlier release of Spring Boot check the “release notes” hosted on the project wiki . You’ll find upgrade instructions along with a list of “new and noteworthy” features for each release.

To upgrade an existing CLI installation use the appropriate package manager command (for example, brew upgrade ) or, if you manually installed the CLI, follow the standard instructions remembering to update your PATH environment variable to remove any older references.

11. Developing Your First Spring Boot Application

This section describes how to develop a simple “Hello World!” web application that highlights some of Spring Boot’s key features. We use Maven to build this project, since most IDEs support it.

Tip

The spring.io web site contains many “Getting Started” guides that use Spring Boot. If you need to solve a specific problem, check there first.

You can shortcut the steps below by going to start.spring.io and choosing the "Web" starter from the dependencies searcher. Doing so generates a new project structure so that you can start coding right away . Check the Spring Initializr documentation for more details.

Before we begin, open a terminal and run the following commands to ensure that you have valid versions of Java and Maven installed:

$ java -version
java version "1.8.0_102"
Java(TM) SE Runtime Environment (build 1.8.0_102-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.102-b14, mixed mode)

$ mvn -v
Apache Maven 3.3.9 (bb52d8502b132ec0a5a3f4c09453c07478323dc5; 2015-11-10T16:41:47+00:00)
Maven home: /usr/local/Cellar/maven/3.3.9/libexec
Java version: 1.8.0_102, vendor: Oracle Corporation

	Note
	This sample needs to be created in its own folder. Subsequent instructions assume that you have created a suitable folder and that it is your “current directory”.

11.1 Creating the POM

We need to start by creating a Maven pom.xml file. The pom.xml is the recipe that is used to build your project. Open your favorite text editor and add the following:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.example</groupId>
	<artifactId>myproject</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.0.0.M7</version>
	</parent>
	<!-- Additional lines to be added here... -->
	<!-- (you don't need this if you are using a .RELEASE version) -->
	<repositories>
		<repository>
			<id>spring-snapshots</id>
			<url>http://repo.spring.io/snapshot</url>
			<snapshots><enabled>true</enabled></snapshots>
		</repository>
		<repository>
			<id>spring-milestones</id>
			<url>http://repo.spring.io/milestone</url>
		</repository>
	</repositories>
	<pluginRepositories>
		<pluginRepository>
			<id>spring-snapshots</id>
			<url>http://repo.spring.io/snapshot</url>
		</pluginRepository>
		<pluginRepository>
			<id>spring-milestones</id>
			<url>http://repo.spring.io/milestone</url>
		</pluginRepository>
	</pluginRepositories>
</project>

The preceding listing should give you a working build. You can test it by running mvn package (for now, you can ignore the “jar will be empty - no content was marked for inclusion!” warning).

	Note
	At this point, you could import the project into an IDE (most modern Java IDEs include built-in support for Maven). For simplicity, we continue to use a plain text editor for this example.

11.2 Adding Classpath Dependencies

Spring Boot provides a number of “Starters” that let you add jars to your classpath. Our sample application has already used spring-boot-starter-parent in the parent section of the POM. The spring-boot-starter-parent is a special starter that provides useful Maven defaults. It also provides a dependency-management section so that you can omit version tags for “blessed” dependencies.

Other “Starters” provide dependencies that you are likely to need when developing a specific type of application. Since we are developing a web application, we add a spring-boot-starter-web dependency. Before that, we can look at what we currently have by running the following command:

$ mvn dependency:tree
[INFO] com.example:myproject:jar:0.0.1-SNAPSHOT

The mvn dependency:tree command prints a tree representation of your project dependencies. You can see that spring-boot-starter-parent provides no dependencies by itself. To add the necessary dependencies, edit your pom.xml and add the spring-boot-starter-web dependency immediately below the parent section:

<dependencies>
	<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-web</artifactId>
	</dependency>
</dependencies>

If you run mvn dependency:tree again, you see that there are now a number of additional dependencies, including the Tomcat web server and Spring Boot itself.

11.3 Writing the Code

To finish our application, we need to create a single Java file. By default, Maven compiles sources from src/main/java , so you need to create that folder structure and then add a file named src/main/java/Example.java to contain the following code:

import org.springframework.boot.*;
import org.springframework.boot.autoconfigure.*;
import org.springframework.web.bind.annotation.*;
@RestController
@EnableAutoConfiguration
public class Example {
	@RequestMapping("/")
	String home() {
		return "Hello World!";
	public static void main(String[] args) throws Exception {
		SpringApplication.run(Example.class, args);
}

Although there is not much code here, quite a lot is going on. We step through the important parts in the next few sections.

11.3.1 The @RestController and @RequestMapping Annotations

The first annotation on our Example class is @RestController . This is known as a stereotype annotation. It provides hints for people reading the code and for Spring that the class plays a specific role. In this case, our class is a web @Controller , so Spring considers it when handling incoming web requests.

The @RequestMapping annotation provides “routing” information. It tells Spring that any HTTP request with the / path should be mapped to the home method. The @RestController annotation tells Spring to render the resulting string directly back to the caller.

	Tip
	The `@RestController` and `@RequestMapping` annotations are Spring MVC annotations. (They are not specific to Spring Boot.) See the MVC section in the Spring Reference Documentation for more details.

11.3.2 The @EnableAutoConfiguration Annotation

The second class-level annotation is @EnableAutoConfiguration . This annotation tells Spring Boot to “guess” how you want to configure Spring, based on the jar dependencies that you have added. Since spring-boot-starter-web added Tomcat and Spring MVC, the auto-configuration assumes that you are developing a web application and sets up Spring accordingly.

11.3.3 The “main” Method

The final part of our application is the main method. This is just a standard method that follows the Java convention for an application entry point. Our main method delegates to Spring Boot’s SpringApplication class by calling run . SpringApplication bootstraps our application, starting Spring, which, in turn, starts the auto-configured Tomcat web server. We need to pass Example.class as an argument to the run method to tell SpringApplication which is the primary Spring component. The args array is also passed through to expose any command-line arguments.

11.4 Running the Example

At this point, your application should work. Since you used the spring-boot-starter-parent POM, you have a useful run goal that you can use to start the application. Type mvn spring-boot:run from the root project directory to start the application. You should see output similar to the following:

$ mvn spring-boot:run
  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::  (v2.0.0.M7)
....... . . .
....... . . . (log output here)
....... . . .
........ Started Example in 2.222 seconds (JVM running for 6.514)

If you open a web browser to localhost:8080 , you should see the following output:

Hello World!

To gracefully exit the application, press ctrl-c .

11.5 Creating an Executable Jar

We finish our example by creating a completely self-contained executable jar file that we could run in production. Executable jars (sometimes called “fat jars”) are archives containing your compiled classes along with all of the jar dependencies that your code needs to run.

To create an executable jar, we need to add the spring-boot-maven-plugin to our pom.xml . To do so, insert the following lines just below the dependencies section:

<build>
	<plugins>
		<plugin>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-maven-plugin</artifactId>
		</plugin>
	</plugins>
</build>

	Note
	The `spring-boot-starter-parent` POM includes `<executions>` configuration to bind the `repackage` goal. If you do not use the parent POM, you need to declare this configuration yourself. See the plugin documentation for details.

Save your pom.xml and run mvn package from the command line, as follows:

$ mvn package
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building myproject 0.0.1-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO] .... ..
[INFO] --- maven-jar-plugin:2.4:jar (default-jar) @ myproject ---
[INFO] Building jar: /Users/developer/example/spring-boot-example/target/myproject-0.0.1-SNAPSHOT.jar
[INFO]
[INFO] --- spring-boot-maven-plugin:2.0.0.M7:repackage (default) @ myproject ---
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------

If you look in the target directory, you should see myproject-0.0.1-SNAPSHOT.jar . The file should be around 10 MB in size. If you want to peek inside, you can use jar tvf , as follows:

$ jar tvf target/myproject-0.0.1-SNAPSHOT.jar

You should also see a much smaller file named myproject-0.0.1-SNAPSHOT.jar.original in the target directory. This is the original jar file that Maven created before it was repackaged by Spring Boot.

To run that application, use the java -jar command, as follows:

$ java -jar target/myproject-0.0.1-SNAPSHOT.jar
  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::  (v2.0.0.M7)
....... . . .
....... . . . (log output here)
....... . . .
........ Started Example in 2.536 seconds (JVM running for 2.864)

As before, to exit the application, press ctrl-c .

12. What to Read Next

Hopefully, this section provided some of the Spring Boot basics and got you on your way to writing your own applications. If you are a task-oriented type of developer, you might want to jump over to spring.io and check out some of the getting started guides that solve specific “How do I do that with Spring?” problems. We also have Spring Boot-specific “ How-to ” reference documentation.

The Spring Boot repository also has a bunch of samples you can run. The samples are independent of the rest of the code (that is, you do not need to build the rest to run or use the samples).

Otherwise, the next logical step is to read Part III, “Using Spring Boot” . If you are really impatient, you could also jump ahead and read about Spring Boot features .

Part III. Using Spring Boot

This section goes into more detail about how you should use Spring Boot. It covers topics such as build systems, auto-configuration, and how to run your applications. We also cover some Spring Boot best practices. Although there is nothing particularly special about Spring Boot (it is just another library that you can consume), there are a few recommendations that, when followed, make your development process a little easier.

If you are starting out with Spring Boot, you should probably read the Getting Started guide before diving into this section.

13. Build Systems

It is strongly recommended that you choose a build system that supports dependency management and that can consume artifacts published to the “Maven Central” repository. We would recommend that you choose Maven or Gradle. It is possible to get Spring Boot to work with other build systems (Ant, for example), but they are not particularly well supported.

13.1 Dependency Management

Each release of Spring Boot provides a curated list of dependencies that it supports. In practice, you do not need to provide a version for any of these dependencies in your build configuration, as Spring Boot is managing that for you. When you upgrade Spring Boot itself, these dependencies are upgraded as well in a consistent way.

	Note
	You can still specify a version and override Spring Boot’s recommendations if you need to do so.

The curated list contains all the spring modules that you can use with Spring Boot as well as a refined list of third party libraries. The list is available as a standard Bills of Materials ( spring-boot-dependencies ) that can be used with both Maven and Gradle .

	Warning
	Each release of Spring Boot is associated with a base version of the Spring Framework. We highly recommend that you not specify its version.

13.2 Maven

Maven users can inherit from the spring-boot-starter-parent project to obtain sensible defaults. The parent project provides the following features:

Java 1.8 as the default compiler level.
UTF-8 source encoding.
A Dependency Management section , inherited from the spring-boot-dependencies pom, that manages the versions of common dependencies. This dependency management lets you omit <version> tags for those dependencies when used in your own pom.
Sensible resource filtering .
Sensible plugin configuration ( exec plugin , Git commit ID , and shade ).
Sensible resource filtering for application.properties and application.yml including profile-specific files (for example, application-foo.properties and application-foo.yml )

Note that, since the application.properties and application.yml files accept Spring style placeholders ( ${…} ), the Maven filtering is changed to use @..@ placeholders. (You can override that by setting a Maven property called resource.delimiter .)

13.2.1 Inheriting the Starter Parent

To configure your project to inherit from the spring-boot-starter-parent set the parent , as follows:

<!-- Inherit defaults from Spring Boot -->
<parent>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-parent</artifactId>
	<version>2.0.0.M7</version>
</parent>

	Note
	You should need to specify only the Spring Boot version number on this dependency. If you import additional starters, you can safely omit the version number.

With that setup, you can also override individual dependencies by overriding a property in your own project. For instance, to upgrade to another Spring Data release train, you would add the following to your pom.xml :

<properties>
	<spring-data-releasetrain.version>Fowler-SR2</spring-data-releasetrain.version>
</properties>

	Tip
	Check the `spring-boot-dependencies` pom for a list of supported properties.

13.2.2 Using Spring Boot without the Parent POM

Not everyone likes inheriting from the spring-boot-starter-parent POM. You may have your own corporate standard parent that you need to use or you may prefer to explicitly declare all your Maven configuration.

If you do not want to use the spring-boot-starter-parent , you can still keep the benefit of the dependency management (but not the plugin management) by using a scope=import dependency, as follows:

<dependencyManagement>
		<dependencies>
		<dependency>
			<!-- Import dependency management from Spring Boot -->
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-dependencies</artifactId>
			<version>2.0.0.M7</version>
			<type>pom</type>
	        <scope>import</scope>
		</dependency>
	</dependencies>
</dependencyManagement>

The preceding sample setup does not let you override individual dependencies by using a property, as explained above. To achieve the same result, you need to add an entry in the dependencyManagement of your project before the spring-boot-dependencies entry. For instance, to upgrade to another Spring Data release train, you could add the following element to your pom.xml :

<dependencyManagement>
	<dependencies>
		<!-- Override Spring Data release train provided by Spring Boot -->
		<dependency>
			<groupId>org.springframework.data</groupId>
			<artifactId>spring-data-releasetrain</artifactId>
			<version>Fowler-SR2</version>
			<scope>import</scope>
			<type>pom</type>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-dependencies</artifactId>
			<version>2.0.0.M7</version>
			<type>pom</type>
			<scope>import</scope>
		</dependency>
	</dependencies>
</dependencyManagement>

	Note
	In the preceding example, we specify a BOM , but any dependency type can be overridden in the same way.

13.2.3 Using the Spring Boot Maven Plugin

Spring Boot includes a Maven plugin that can package the project as an executable jar. Add the plugin to your <plugins> section if you want to use it, as shown in the following example:

<build>
	<plugins>
		<plugin>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-maven-plugin</artifactId>
		</plugin>
	</plugins>
</build>

	Note
	If you use the Spring Boot starter parent pom, you need to add only the plugin. There is no need to configure it unless you want to change the settings defined in the parent.

13.3 Gradle

To learn about using Spring Boot with Gradle, please refer to the documentation for Spring Boot’s Gradle plugin:

Reference ( HTML and PDF )
API

13.4 Ant

It is possible to build a Spring Boot project using Apache Ant+Ivy. The spring-boot-antlib “AntLib” module is also available to help Ant create executable jars.

To declare dependencies, a typical ivy.xml file looks something like the following example:

<ivy-module version="2.0">
	<info organisation="org.springframework.boot" module="spring-boot-sample-ant" />
	<configurations>
		<conf name="compile" description="everything needed to compile this module" />
		<conf name="runtime" extends="compile" description="everything needed to run this module" />
	</configurations>
	<dependencies>
		<dependency org="org.springframework.boot" name="spring-boot-starter"
			rev="${spring-boot.version}" conf="compile" />
	</dependencies>
</ivy-module>

A typical build.xml looks like the following example:

<project
	xmlns:ivy="antlib:org.apache.ivy.ant"
	xmlns:spring-boot="antlib:org.springframework.boot.ant"
	name="myapp" default="build">
	<property name="spring-boot.version" value="2.0.0.M7" />
	<target name="resolve" description="--> retrieve dependencies with ivy">
		<ivy:retrieve pattern="lib/[conf]/[artifact]-[type]-[revision].[ext]" />
	</target>
	<target name="classpaths" depends="resolve">
		<path id="compile.classpath">
			<fileset dir="lib/compile" includes="*.jar" />
		</path>
	</target>
	<target name="init" depends="classpaths">
		<mkdir dir="build/classes" />
	</target>
	<target name="compile" depends="init" description="compile">
		<javac srcdir="src/main/java" destdir="build/classes" classpathref="compile.classpath" />
	</target>
	<target name="build" depends="compile">
		<spring-boot:exejar destfile="build/myapp.jar" classes="build/classes">
			<spring-boot:lib>
				<fileset dir="lib/runtime" />
			</spring-boot:lib>
		</spring-boot:exejar>
	</target>
</project>

	Tip
	If you do not want to use the `spring-boot-antlib` module, see the Section 85.9, “Build an Executable Archive from Ant without Using `spring-boot-antlib` ” “How-to” .

13.5 Starters

Starters are a set of convenient dependency descriptors that you can include in your application. You get a one-stop shop for all the Spring and related technology that you need without having to hunt through sample code and copy-paste loads of dependency descriptors. For example, if you want to get started using Spring and JPA for database access, include the spring-boot-starter-data-jpa dependency in your project.

The starters contain a lot of the dependencies that you need to get a project up and running quickly and with a consistent, supported set of managed transitive dependencies.

The following application starters are provided by Spring Boot under the org.springframework.boot group:

Table 13.1. Spring Boot application starters

Name	Description	Pom
`spring-boot-starter`	Core starter, including auto-configuration support, logging and YAML	Pom
`spring-boot-starter-activemq`	Starter for JMS messaging using Apache ActiveMQ	Pom
`spring-boot-starter-amqp`	Starter for using Spring AMQP and Rabbit MQ	Pom
`spring-boot-starter-aop`	Starter for aspect-oriented programming with Spring AOP and AspectJ	Pom
`spring-boot-starter-artemis`	Starter for JMS messaging using Apache Artemis	Pom
`spring-boot-starter-batch`	Starter for using Spring Batch	Pom
`spring-boot-starter-cache`	Starter for using Spring Framework’s caching support	Pom
`spring-boot-starter-cloud-connectors`	Starter for using Spring Cloud Connectors which simplifies connecting to services in cloud platforms like Cloud Foundry and Heroku	Pom
`spring-boot-starter-data-cassandra`	Starter for using Cassandra distributed database and Spring Data Cassandra	Pom
`spring-boot-starter-data-cassandra-reactive`	Starter for using Cassandra distributed database and Spring Data Cassandra Reactive	Pom
`spring-boot-starter-data-couchbase`	Starter for using Couchbase document-oriented database and Spring Data Couchbase	Pom
`spring-boot-starter-data-couchbase-reactive`	Starter for using Couchbase document-oriented database and Spring Data Couchbase Reactive	Pom
`spring-boot-starter-data-elasticsearch`	Starter for using Elasticsearch search and analytics engine and Spring Data Elasticsearch	Pom
`spring-boot-starter-data-jpa`	Starter for using Spring Data JPA with Hibernate	Pom
`spring-boot-starter-data-ldap`	Starter for using Spring Data LDAP	Pom
`spring-boot-starter-data-mongodb`	Starter for using MongoDB document-oriented database and Spring Data MongoDB	Pom
`spring-boot-starter-data-mongodb-reactive`	Starter for using MongoDB document-oriented database and Spring Data MongoDB Reactive	Pom
`spring-boot-starter-data-neo4j`	Starter for using Neo4j graph database and Spring Data Neo4j	Pom
`spring-boot-starter-data-redis`	Starter for using Redis key-value data store with Spring Data Redis and the Lettuce client	Pom
`spring-boot-starter-data-redis-reactive`	Starter for using Redis key-value data store with Spring Data Redis reactive and the Lettuce client	Pom
`spring-boot-starter-data-rest`	Starter for exposing Spring Data repositories over REST using Spring Data REST	Pom
`spring-boot-starter-data-solr`	Starter for using the Apache Solr search platform with Spring Data Solr	Pom
`spring-boot-starter-freemarker`	Starter for building MVC web applications using FreeMarker views	Pom
`spring-boot-starter-groovy-templates`	Starter for building MVC web applications using Groovy Templates views	Pom
`spring-boot-starter-hateoas`	Starter for building hypermedia-based RESTful web application with Spring MVC and Spring HATEOAS	Pom
`spring-boot-starter-integration`	Starter for using Spring Integration	Pom
`spring-boot-starter-jdbc`	Starter for using JDBC with the Tomcat JDBC connection pool	Pom
`spring-boot-starter-jersey`	Starter for building RESTful web applications using JAX-RS and Jersey. An alternative to `spring-boot-starter-web`	Pom
`spring-boot-starter-jooq`	Starter for using jOOQ to access SQL databases. An alternative to `spring-boot-starter-data-jpa` or `spring-boot-starter-jdbc`	Pom
`spring-boot-starter-json`	Starter for reading and writing json	Pom
`spring-boot-starter-jta-atomikos`	Starter for JTA transactions using Atomikos	Pom
`spring-boot-starter-jta-bitronix`	Starter for JTA transactions using Bitronix	Pom
`spring-boot-starter-jta-narayana`	Spring Boot Narayana JTA Starter	Pom
`spring-boot-starter-mail`	Starter for using Java Mail and Spring Framework’s email sending support	Pom
`spring-boot-starter-mustache`	Starter for building web applications using Mustache views	Pom
`spring-boot-starter-quartz`	Spring Boot Quartz Starter	Pom
`spring-boot-starter-security`	Starter for using Spring Security	Pom
`spring-boot-starter-test`	Starter for testing Spring Boot applications with libraries including JUnit, Hamcrest and Mockito	Pom
`spring-boot-starter-thymeleaf`	Starter for building MVC web applications using Thymeleaf views	Pom
`spring-boot-starter-validation`	Starter for using Java Bean Validation with Hibernate Validator	Pom
`spring-boot-starter-web`	Starter for building web, including RESTful, applications using Spring MVC. Uses Tomcat as the default embedded container	Pom
`spring-boot-starter-web-services`	Starter for using Spring Web Services	Pom
`spring-boot-starter-webflux`	Starter for building WebFlux applications using Spring Framework’s Reactive Web support	Pom
`spring-boot-starter-websocket`	Starter for building WebSocket applications using Spring Framework’s WebSocket support	Pom

In addition to the application starters, the following starters can be used to add production ready features:

Table 13.2. Spring Boot production starters

Name	Description	Pom
`spring-boot-starter-actuator`	Starter for using Spring Boot’s Actuator which provides production ready features to help you monitor and manage your application	Pom

Finally, Spring Boot also includes the following starters that can be used if you want to exclude or swap specific technical facets:

Table 13.3. Spring Boot technical starters

Name	Description	Pom
`spring-boot-starter-jetty`	Starter for using Jetty as the embedded servlet container. An alternative to `spring-boot-starter-tomcat`	Pom
`spring-boot-starter-log4j2`	Starter for using Log4j2 for logging. An alternative to `spring-boot-starter-logging`	Pom
`spring-boot-starter-logging`	Starter for logging using Logback. Default logging starter	Pom
`spring-boot-starter-reactor-netty`	Starter for using Reactor Netty as the embedded reactive HTTP server.	Pom
`spring-boot-starter-tomcat`	Starter for using Tomcat as the embedded servlet container. Default servlet container starter used by `spring-boot-starter-web`	Pom
`spring-boot-starter-undertow`	Starter for using Undertow as the embedded servlet container. An alternative to `spring-boot-starter-tomcat`	Pom

	Tip
	For a list of additional community contributed starters, see the README file in the `spring-boot-starters` module on GitHub.

14. Structuring Your Code

Spring Boot does not require any specific code layout to work. However, there are some best practices that help.

14.1 Using the “default” Package

When a class does not include a package declaration, it is considered to be in the “default package”. The use of the “default package” is generally discouraged and should be avoided. It can cause particular problems for Spring Boot applications that use the @ComponentScan , @EntityScan , or @SpringBootApplication annotations, since every class from every jar is read.

	Tip
	We recommend that you follow Java’s recommended package naming conventions and use a reversed domain name (for example, `com.example.project` ).

14.2 Locating the Main Application Class

We generally recommend that you locate your main application class in a root package above other classes. The @EnableAutoConfiguration annotation is often placed on your main class, and it implicitly defines a base “search package” for certain items. For example, if you are writing a JPA application, the package of the @EnableAutoConfiguration annotated class is used to search for @Entity items.

Using a root package also lets the @ComponentScan annotation be used without needing to specify a basePackage attribute. You can also use the @SpringBootApplication annotation if your main class is in the root package.

The following listing shows a typical layout:

com
 +- example
     +- myapplication
         +- Application.java
         +- customer
         |   +- Customer.java
         |   +- CustomerController.java
         |   +- CustomerService.java
         |   +- CustomerRepository.java
         +- order
             +- Order.java
             +- OrderController.java
             +- OrderService.java
             +- OrderRepository.java

The Application.java file would declare the main method, along with the basic @Configuration , as follows:

package com.example.myapplication;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
@Configuration
@EnableAutoConfiguration
@ComponentScan
public class Application {
	public static void main(String[] args) {
		SpringApplication.run(Application.class, args);
}

15. Configuration Classes

Spring Boot favors Java-based configuration. Although it is possible to use SpringApplication with XML sources, we generally recommend that your primary source be a single @Configuration class. Usually the class that defines the main method is a good candidate as the primary @Configuration .

	Tip
	Many Spring configuration examples have been published on the Internet that use XML configuration. If possible, always try to use the equivalent Java-based configuration. Searching for `Enable*` annotations can be a good starting point.

15.1 Importing Additional Configuration Classes

You need not put all your @Configuration into a single class. The @Import annotation can be used to import additional configuration classes. Alternatively, you can use @ComponentScan to automatically pick up all Spring components, including @Configuration classes.

15.2 Importing XML Configuration

If you absolutely must use XML based configuration, we recommend that you still start with a @Configuration class. You can then use an @ImportResource annotation to load XML configuration files.

16. Auto-configuration

Spring Boot auto-configuration attempts to automatically configure your Spring application based on the jar dependencies that you have added. For example, if HSQLDB is on your classpath, and you have not manually configured any database connection beans, then Spring Boot auto-configures an in-memory database.

You need to opt-in to auto-configuration by adding the @EnableAutoConfiguration or @SpringBootApplication annotations to one of your @Configuration classes.

	Tip
	You should only ever add one `@EnableAutoConfiguration` annotation. We generally recommend that you add it to your primary `@Configuration` class.

16.1 Gradually Replacing Auto-configuration

Auto-configuration is non-invasive. At any point, you can start to define your own configuration to replace specific parts of the auto-configuration. For example, if you add your own DataSource bean, the default embedded database support backs away.

If you need to find out what auto-configuration is currently being applied, and why, start your application with the --debug switch. Doing so enables debug logs for a selection of core loggers and logs a conditions report to the console.

16.2 Disabling Specific Auto-configuration Classes

If you find that specific auto-configuration classes that you do not want are being applied, you can use the exclude attribute of @EnableAutoConfiguration to disable them, as shown in the following example:

import org.springframework.boot.autoconfigure.*;
import org.springframework.boot.autoconfigure.jdbc.*;
import org.springframework.context.annotation.*;
@Configuration
@EnableAutoConfiguration(exclude={DataSourceAutoConfiguration.class})
public class MyConfiguration {
}

If the class is not on the classpath, you can use the excludeName attribute of the annotation and specify the fully qualified name instead. Finally, you can also control the list of auto-configuration classes to exclude by using the spring.autoconfigure.exclude property.

	Tip
	You can define exclusions both at the annotation level and by using the property.

17. Spring Beans and Dependency Injection

You are free to use any of the standard Spring Framework techniques to define your beans and their injected dependencies. For simplicity, we often find that using @ComponentScan (to find your beans) and using @Autowired (to do constructor injection) works well.

If you structure your code as suggested above (locating your application class in a root package), you can add @ComponentScan without any arguments. All of your application components ( @Component , @Service , @Repository , @Controller etc.) are automatically registered as Spring Beans.

The following example shows a @Service Bean that uses constructor injection to obtain a required RiskAssessor bean:

package com.example.service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class DatabaseAccountService implements AccountService {
	private final RiskAssessor riskAssessor;
	@Autowired
	public DatabaseAccountService(RiskAssessor riskAssessor) {
		this.riskAssessor = riskAssessor;
	// ...
}

If a bean has one constructor, you can omit the @Autowired , as shown in the following example:

@Service
public class DatabaseAccountService implements AccountService {
	private final RiskAssessor riskAssessor;
	public DatabaseAccountService(RiskAssessor riskAssessor) {
		this.riskAssessor = riskAssessor;
	// ...
}

	Tip
	Notice how using constructor injection lets the `riskAssessor` field be marked as `final` , indicating that it cannot be subsequently changed.

18. Using the @SpringBootApplication Annotation

Many Spring Boot developers always have their main class annotated with @Configuration , @EnableAutoConfiguration , and @ComponentScan . Since these annotations are so frequently used together (especially if you follow the best practices above), Spring Boot provides a convenient @SpringBootApplication alternative.

The @SpringBootApplication annotation is equivalent to using @Configuration , @EnableAutoConfiguration , and @ComponentScan with their default attributes, as shown in the following example:

package com.example.myapplication;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication // same as @Configuration @EnableAutoConfiguration @ComponentScan
public class Application {
	public static void main(String[] args) {
		SpringApplication.run(Application.class, args);
}

	Note
	`@SpringBootApplication` also provides aliases to customize the attributes of `@EnableAutoConfiguration` and `@ComponentScan` .

19. Running Your Application

One of the biggest advantages of packaging your application as a jar and using an embedded HTTP server is that you can run your application as you would any other. Debugging Spring Boot applications is also easy. You do not need any special IDE plugins or extensions.

	Note
	This section only covers jar based packaging. If you choose to package your application as a war file, you should refer to your server and IDE documentation.

19.1 Running from an IDE

You can run a Spring Boot application from your IDE as a simple Java application. However, you first need to import your project. Import steps vary depending on your IDE and build system. Most IDEs can import Maven projects directly. For example, Eclipse users can select Import… → Existing Maven Projects from the File menu.

If you cannot directly import your project into your IDE, you may be able to generate IDE metadata by using a build plugin. Maven includes plugins for Eclipse and IDEA . Gradle offers plugins for various IDEs .

	Tip
	If you accidentally run a web application twice, you see a “Port already in use” error. STS users can use the `Relaunch` button rather than the `Run` button to ensure that any existing instance is closed.

19.2 Running as a Packaged Application

If you use the Spring Boot Maven or Gradle plugins to create an executable jar, you can run your application using java -jar , as shown in the following example:

$ java -jar target/myapplication-0.0.1-SNAPSHOT.jar

It is also possible to run a packaged application with remote debugging support enabled. Doing so lets you attach a debugger to your packaged application, as shown in the following example:

$ java -Xdebug -Xrunjdwp:server=y,transport=dt_socket,address=8000,suspend=n \
       -jar target/myapplication-0.0.1-SNAPSHOT.jar

19.3 Using the Maven Plugin

The Spring Boot Maven plugin includes a run goal that can be used to quickly compile and run your application. Applications run in an exploded form, as they do in your IDE.

$ mvn spring-boot:run

You might also want to use the MAVEN_OPTS operating system environment variable, as shown in the following example:

$ export MAVEN_OPTS=-Xmx1024m

19.4 Using the Gradle Plugin

The Spring Boot Gradle plugin also includes a bootRun task that can be used to run your application in an exploded form. The bootRun task is added whenever you apply the org.springframework.boot and java plugins and is shown in the following example:

$ gradle bootRun

You might also want to use the JAVA_OPTS operating system environment variable, as shown in the following example:

$ export JAVA_OPTS=-Xmx1024m

19.5 Hot Swapping

Since Spring Boot applications are just plain Java applications, JVM hot-swapping should work out of the box. JVM hot swapping is somewhat limited with the bytecode that it can replace. For a more complete solution, JRebel can be used.

The spring-boot-devtools module also includes support for quick application restarts. See the Chapter 20, Developer Tools section below and the Hot swapping “How-to” for details.

20. Developer Tools

Spring Boot includes an additional set of tools that can make the application development experience a little more pleasant. The spring-boot-devtools module can be included in any project to provide additional development-time features. To include devtools support, add the module dependency to your build, as shown in the following listings for Maven and Gradle:

Maven.

<dependencies>
	<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-devtools</artifactId>
		<optional>true</optional>
	</dependency>
</dependencies>

Gradle.

dependencies {
	compile("org.springframework.boot:spring-boot-devtools")
Note
Developer tools are automatically disabled when running a fully packaged
application. If your application is launched using java -jar or if it is started from a
special classloader, then it is considered a “production application”. Flagging the
dependency as optional is a best practice that prevents devtools from being transitively
applied to other modules using your project. Gradle does not support optional
dependencies out-of-the-box, so you may want to have a look at the
propdeps-plugin.
Tip
Repackaged archives do not contain devtools by default. If you want to use a
certain remote devtools feature, you need to disable the
excludeDevtools build property to include it. The property is supported with both the
Maven and Gradle plugins.20.1 Property Defaults
Several of the libraries supported by Spring Boot use caches to improve performance. For
example, template
engines cache compiled templates to avoid repeatedly parsing template files. Also,
Spring MVC can add HTTP caching headers to responses when serving static resources.
While caching is very beneficial in production, it can be counter-productive during
development, preventing you from seeing the changes you just made in your application.
For this reason, spring-boot-devtools disables the caching options by default.
Cache options are usually configured by settings in your application.properties file.
For example, Thymeleaf offers the spring.thymeleaf.cache property. Rather than needing
to set these properties manually, the spring-boot-devtools module automatically applies
sensible development-time configuration.
Tip
For a complete list of the properties that are applied by the devtools, see
DevToolsPropertyDefaultsPostProcessor.
20.2 Automatic Restart
Applications that use spring-boot-devtools automatically restart whenever files on the
classpath change. This can be a useful feature when working in an IDE, as it gives a very
fast feedback loop for code changes. By default, any entry on the classpath that points
to a folder is monitored for changes. Note that certain resources, such as static assets
and view templates, do not need to restart the
application.
Triggering a restart
As DevTools monitors classpath resources, the only way to trigger a restart is to update
the classpath. The way in which you cause the classpath to be updated depends on the IDE
that you are using. In Eclipse, saving a modified file causes the classpath to be updated
and triggers a restart. In IntelliJ IDEA, building the project
(Build -> Make Project) has the same effect.
Note
As long as forking is enabled, you can also start your application by using the supported
build plugins (Maven and Gradle), since DevTools needs an isolated application
classloader to operate properly. By default, Gradle and Maven do that when they detect
DevTools on the classpath.
Tip
Automatic restart works very well when used with LiveReload.
See the LiveReload section for details. If you use
JRebel, automatic restarts are disabled in favor of dynamic class reloading. Other
devtools features (such as LiveReload and property overrides) can still be used.




    
Note
DevTools relies on the application context’s shutdown hook to close it during a
restart. It does not work correctly if you have disabled the shutdown hook
(SpringApplication.setRegisterShutdownHook(false)).
Note
When deciding if an entry on the classpath should trigger a restart when it
changes, DevTools automatically ignores projects named spring-boot,
spring-boot-devtools, spring-boot-autoconfigure, spring-boot-actuator, and
spring-boot-starter.
Note
DevTools needs to customize the ResourceLoader used by the ApplicationContext.
If your application provides one already, it is going to be wrapped. Direct override of
the getResource method on the ApplicationContext is not supported.
Restart vs Reload
The restart technology provided by Spring Boot works by using two classloaders. Classes
that do not change (for example, those from third-party jars) are loaded into a base
classloader. Classes that you are actively developing are loaded into a restart
classloader. When the application is restarted, the restart classloader is thrown away
and a new one is created. This approach means that application restarts are typically
much faster than “cold starts”, since the base classloader is already available and
populated.If you find that restarts are not quick enough for your applications or you encounter
classloading issues, you could consider reloading technologies such as
JRebel from ZeroTurnaround. These work by
rewriting classes as they are loaded to make them more amenable to reloading.
20.2.1 Logging changes in condition evaluation
By default, each time your application restarts, a report showing the condition evaluation
delta is logged. The report shows the changes to your application’s auto-configuration as
you make changes such as adding or removing beans and setting configuration properties.
To disable the logging of the report, set the following property:
spring.devtools.restart.log-condition-evaluation-delta=false
20.2.2 Excluding Resources
Certain resources do not necessarily need to trigger a restart when they are changed. For
example, Thymeleaf templates can be edited in-place. By default, changing resources
in /META-INF/maven, /META-INF/resources, /resources, /static, /public, or
/templates does not trigger a restart but does trigger a
live reload. If you want to customize these
exclusions, you can use the spring.devtools.restart.exclude property. For example, to
exclude only /static and /public you would set the following property:
spring.devtools.restart.exclude=static/**,public/**
Tip
If you want to keep those defaults and add additional exclusions, use the
spring.devtools.restart.additional-exclude property instead.
20.2.3 Watching Additional Paths
You may want your application to be restarted or reloaded when you make changes to files
that are not on the classpath. To do so, use the
spring.devtools.restart.additional-paths property to configure additional paths to
watch for changes. You can use the spring.devtools.restart.exclude property
described above to control whether changes
beneath the additional paths trigger a full restart or a
live reload.
20.2.4 Disabling Restart
If you do not want to use the restart feature, you can disable it by using the
spring.devtools.restart.enabled property. In most cases, you can set this property in
your application.properties (doing so still initializes the restart classloader, but it
does not watch for file changes).
If you need to completely disable restart support (for example, because it doesn’t work
with a specific library), you need to set the spring.devtools.restart.enabled System
property to false before calling SpringApplication.run(…), as shown in the
following example:
public static void main(String[] args) {
	System.setProperty("spring.devtools.restart.enabled", "false");
	SpringApplication.run(MyApp.class, args);
}
20.2.5 Using a Trigger File
If you work with an IDE that continuously compiles changed files, you might prefer to
trigger restarts only at specific times. To do so, you can use a “trigger file”, which
is a special file that must be modified when you want to actually trigger a restart
check. Changing the file only triggers the check and the restart will only occur if
Devtools has detected it has to do something. The trigger file can be updated manually or
with an IDE plugin.
To use a trigger file, set the spring.devtools.restart.trigger-file property to the
path of your trigger file.
Tip
You might want to set spring.devtools.restart.trigger-file as a
global setting, so that all your projects behave
in the same way.
20.2.6 Customizing the Restart Classloader
As described in the Restart vs Reload section above, restart
functionality is implemented by using two classloaders. For most applications, this
approach works well. However, sometimes it can cause classloading issues.
By default, any open project in your IDE is loaded with the “restart” classloader, and
any regular .jar file is loaded with the “base” classloader. If you work on a
multi-module project, and not every module is imported into your IDE, you may need to
customize things. To do so, you can create a META-INF/spring-devtools.properties file.
The spring-devtools.properties file can contain properties prefixed with
restart.exclude and restart.include. The include elements are items that should be
pulled up into the “restart” classloader, and the exclude elements are items that
should be pushed down into the “base” classloader. The value of the property is a regex
pattern that is applied to the classpath, as shown in the following example:
restart.exclude.companycommonlibs=/mycorp-common-[\\w-]+\.jar
restart.include.projectcommon=/mycorp-myproj-[\\w-]+\.jar
Note
All property keys must be unique. As long as a property starts with
restart.include. or restart.exclude. it is considered.
Tip
All META-INF/spring-devtools.properties from the classpath will be loaded. You can
package files inside your project, or in the libraries that the project consumes.
20.2.7 Known Limitations
Restart functionality does not work well with objects that are deserialized by using a
standard ObjectInputStream. If you need to deserialize data, you may need to use
Spring’s ConfigurableObjectInputStream in combination with
Thread.currentThread().getContextClassLoader().
Unfortunately, several third-party libraries deserialize without considering the context
classloader. If you find such a problem, you need to request a fix with the original
authors.
20.3 LiveReload
The spring-boot-devtools module includes an embedded LiveReload server that can be used
to trigger a browser refresh when a resource is changed. LiveReload browser extensions
are freely available for Chrome, Firefox and Safari from
livereload.com.
If you do not want to start the LiveReload server when your application runs, you can set
the spring.devtools.livereload.enabled property to false.
Note
You can only run one LiveReload server at a time. Before starting your application,
ensure that no other LiveReload servers are running. If you start multiple applications
from your IDE, only the first has LiveReload support.
20.4 Global Settings
You can configure global devtools settings by adding a file named
.spring-boot-devtools.properties to your $HOME folder (note that the filename starts
with “.”). Any properties added to this file apply to all Spring Boot applications on
your machine that use devtools. For example, to configure restart to always use a
trigger file, you would add the following
property:
~/.spring-boot-devtools.properties. 
spring.devtools.reload.trigger-file=.reloadtrigger

20.5 Remote Applications
The Spring Boot developer tools are not just limited to local development. You can also
use several features when running applications remotely. Remote support is opt-in. To
enable it, you need to make sure that devtools is included in the repackaged archive,
as shown in the following listing:
<build>
	<plugins>
		<plugin>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-maven-plugin</artifactId>
			<configuration>
				<excludeDevtools>false</excludeDevtools>
			</configuration>
		</plugin>
	</plugins>
</build>
Then you need to set a spring.devtools.remote.secret property, as shown in the
following example:
spring.devtools.remote.secret=mysecret
Warning
Enabling spring-boot-devtools on a remote application is a security risk. You
should never enable support on a production deployment.




    
Remote devtools support is provided in two parts: a server-side endpoint that accepts
connections and a client application that you run in your IDE. The server component is
automatically enabled when the spring.devtools.remote.secret property is set. The
client component must be launched manually.
20.5.1 Running the Remote Client Application
The remote client application is designed to be run from within your IDE. You need to run
org.springframework.boot.devtools.RemoteSpringApplication with the same classpath as
the remote project that you connect to. The application’s single required argument is the
remote URL to which it connects.
For example, if you are using Eclipse or STS and you have a project named my-app that
you have deployed to Cloud Foundry, you would do the following:
Select Run Configurations… from the Run menu.
Create a new Java Application “launch configuration”.
Browse for the my-app project.
Use org.springframework.boot.devtools.RemoteSpringApplication as the main class.
Add https://myapp.cfapps.io to the Program arguments (or whatever your remote
URL is).
A running remote client might resemble the following listing:
  .   ____          _                                              __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _          ___               _      \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` |        | _ \___ _ __  ___| |_ ___ \ \ \ \
 \\/  ___)| |_)| | | | | || (_| []::::::[]   / -_) '  \/ _ \  _/ -_) ) ) ) )
  '  |____| .__|_| |_|_| |_\__, |        |_|_\___|_|_|_\___/\__\___|/ / / /
 =========|_|==============|___/===================================/_/_/_/
 :: Spring Boot Remote :: 2.0.0.M7
2015-06-10 18:25:06.632  INFO 14938 --- [           main] o.s.b.devtools.RemoteSpringApplication   : Starting RemoteSpringApplication on pwmbp with PID 14938 (/Users/pwebb/projects/spring-boot/code/spring-boot-devtools/target/classes started by pwebb in /Users/pwebb/projects/spring-boot/code/spring-boot-samples/spring-boot-sample-devtools)
2015-06-10 18:25:06.671  INFO 14938 --- [           main] s.c.a.AnnotationConfigApplicationContext : Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@2a17b7b6: startup date [Wed Jun 10 18:25:06 PDT 2015]; root of context hierarchy
2015-06-10 18:25:07.043  WARN 14938 --- [           main] o.s.b.d.r.c.RemoteClientConfiguration    : The connection to http://localhost:8080 is insecure. You should use a URL starting with 'https://'.
2015-06-10 18:25:07.074  INFO 14938 --- [           main] o.s.b.d.a.OptionalLiveReloadServer       : LiveReload server is running on port 35729
2015-06-10 18:25:07.130  INFO 14938 --- [           main] o.s.b.devtools.RemoteSpringApplication   : Started RemoteSpringApplication in 0.74 seconds (JVM running for 1.105)
Note
Because the remote client is using the same classpath as the real application it
can directly read application properties. This is how the spring.devtools.remote.secret
property is read and passed to the server for authentication.
Tip
It is always advisable to use https:// as the connection protocol, so that traffic
is encrypted and passwords cannot be intercepted.
Tip
If you need to use a proxy to access the remote application, configure the
spring.devtools.remote.proxy.host and spring.devtools.remote.proxy.port properties.
20.5.2 Remote Update
The remote client monitors your application classpath for changes in the same way as the
local restart. Any updated resource is pushed to the
remote application and (if required) triggers a restart. This can be helpful if you
iterate on a feature that uses a cloud service that you do not have locally. Generally,
remote updates and restarts are much quicker than a full rebuild and deploy cycle.
Note
Files are only monitored when the remote client is running. If you change a file
before starting the remote client, it is not pushed to the remote server.

21. Packaging Your Application for Production

Executable jars can be used for production deployment. As they are self-contained, they are also ideally suited for cloud-based deployment.

For additional “production ready” features, such as health, auditing, and metric REST or JMX end-points, consider adding spring-boot-actuator . See Part V, “Spring Boot Actuator: Production-ready features” for details.

22. What to Read Next

You should now understand how you can use Spring Boot and some best practices that you should follow. You can now go on to learn about specific Spring Boot features in depth, or you could skip ahead and read about the “ production ready ” aspects of Spring Boot.

Part IV. Spring Boot features

This section dives into the details of Spring Boot. Here you can learn about the key features that you may want to use and customize. If you have not already done so, you might want to read the " Part II, “Getting Started” " and " Part III, “Using Spring Boot” " sections so that you have a good grounding of the basics.

23. SpringApplication

The SpringApplication class provides a convenient way to bootstrap a Spring application that is started from a main() method. In many situations, you can delegate to the static SpringApplication.run method, as shown in the following example:

public static void main(String[] args) {
	SpringApplication.run(MySpringConfiguration.class, args);
}

When your application starts, you should see something similar to the following output:

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::   v2.0.0.M7
2013-07-31 00:08:16.117  INFO 56603 --- [           main] o.s.b.s.app.SampleApplication            : Starting SampleApplication v0.1.0 on mycomputer with PID 56603 (/apps/myapp.jar started by pwebb)
2013-07-31 00:08:16.166  INFO 56603 --- [           main] ationConfigServletWebServerApplicationContext : Refreshing org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext@6e5a8246: startup date [Wed Jul 31 00:08:16 PDT 2013]; root of context hierarchy
2014-03-04 13:09:54.912  INFO 41370 --- [           main] .t.TomcatServletWebServerFactory : Server initialized with port: 8080
2014-03-04 13:09:56.501  INFO 41370 --- [           main] o.s.b.s.app.SampleApplication            : Started SampleApplication in 2.992 seconds (JVM running for 3.658)

By default, INFO logging messages are shown, including some relevant startup details, such as the user that launched the application.

23.1 Startup Failure

If your application fails to start, registered FailureAnalyzers get a chance to provide a dedicated error message and a concrete action to fix the problem. For instance, if you start a web application on port 8080 and that port is already in use, you should see something similar to the following message:

***************************
APPLICATION FAILED TO START
***************************
Description:
Embedded servlet container failed to start. Port 8080 was already in use.
Action:
Identify and stop the process that's listening on port 8080 or configure this application to listen on another port.

	Note
	Spring Boot provides numerous `FailureAnalyzer` implementations, and you can add your own .

If no failure analyzers are able to handle the exception, you can still display the full conditions report to better understand what went wrong. To do so, you need to enable the debug property or enable DEBUG logging for org.springframework.boot.autoconfigure.logging.ConditionEvaluationReportLoggingListener .

For instance, if you are running your application by using java -jar , you can enable the debug property as follows:

$ java -jar myproject-0.0.1-SNAPSHOT.jar --debug

23.2 Customizing the Banner

The banner that is printed on start up can be changed by adding a banner.txt file to your classpath or by setting the banner.location property to the location of such a file. If the file has an encoding other than UTF-8, you can set banner.charset . In addition to a text file, you can also add a banner.gif , banner.jpg , or banner.png image file to your classpath or set the banner.image.location property. Images are converted into an ASCII art representation and printed above any text banner.

Inside your banner.txt file, you can use any of the following placeholders:

Table 23.1. Banner variables

Variable	Description
`${application.version}`	The version number of your application, as declared in `MANIFEST.MF` . For example, `Implementation-Version: 1.0` is printed as `1.0` .
`${application.formatted-version}`	The version number of your application, as declared in `MANIFEST.MF` and formatted for display (surrounded with brackets and prefixed with `v` ). For example `(v1.0)` .
`${spring-boot.version}`	The Spring Boot version that you are using. For example `2.0.0.M7` .
`${spring-boot.formatted-version}`	The Spring Boot version that you are using, formatted for display (surrounded with brackets and prefixed with `v` ). For example `(v2.0.0.M7)` .
`${Ansi.NAME}` (or `${AnsiColor.NAME}` , `${AnsiBackground.NAME}` , `${AnsiStyle.NAME}` )	Where `NAME` is the name of an ANSI escape code. See `AnsiPropertySource` for details.
`${application.title}`	The title of your application, as declared in `MANIFEST.MF` . For example `Implementation-Title: MyApp` is printed as `MyApp` .

	Tip
	The `SpringApplication.setBanner(…)` method can be used if you want to generate a banner programmatically. Use the `org.springframework.boot.Banner` interface and implement your own `printBanner()` method.

You can also use the spring.main.banner-mode property to determine if the banner has to be printed on System.out ( console ), sent to the configured logger ( log ), or not produced at all ( off ).

The printed banner is registered as a singleton bean under the following name: springBootBanner .

Note

YAML maps off to false , so be sure to add quotes if you want to disable the banner in your application.

spring:
	main:
		banner-mode: "off"

23.3 Customizing SpringApplication

If the SpringApplication defaults are not to your taste, you can instead create a local instance and customize it. For example, to turn off the banner, you could write:

public static void main(String[] args) {
	SpringApplication app = new SpringApplication(MySpringConfiguration.class);
	app.setBannerMode(Banner.Mode.OFF);
	app.run(args);
}

	Note
	The constructor arguments passed to `SpringApplication` are configuration sources for spring beans. In most cases, these are references to `@Configuration` classes, but they could also be references to XML configuration or to packages that should be scanned.

It is also possible to configure the SpringApplication by using an application.properties file. See Chapter 24, Externalized Configuration for details.

For a complete list of the configuration options, see the SpringApplication Javadoc .

23.4 Fluent Builder API

If you need to build an ApplicationContext hierarchy (multiple contexts with a parent/child relationship) or if you just prefer using a ‘fluent’ builder API, you can use the SpringApplicationBuilder .

The SpringApplicationBuilder lets you chain together multiple method calls and includes parent and child methods that let you create a hierarchy, as shown in the following example:

new SpringApplicationBuilder()
		.sources(Parent.class)
		.child(Application.class)
		.bannerMode(Banner.Mode.OFF)
		.run(args);

	Note
	There are some restrictions when creating an `ApplicationContext` hierarchy. For example, Web components must be contained within the child context, and the same `Environment` is used for both parent and child contexts. See the `SpringApplicationBuilder` Javadoc for full details.

23.5 Application Events and Listeners

In addition to the usual Spring Framework events, such as ContextRefreshedEvent , a SpringApplication sends some additional application events.

Note

Some events are actually triggered before the ApplicationContext is created, so you cannot register a listener on those as a @Bean . You can register them with the SpringApplication.addListeners(…) or SpringApplicationBuilder.listeners(…) methods.

If you want those listeners to be registered automatically, regardless of the way the application is created, you can add a META-INF/spring.factories file to your project and reference your listener(s) by using the org.springframework.context.ApplicationListener key, as shown in the following example:

org.springframework.context.ApplicationListener=com.example.project.MyListener

Application events are sent in the following order, as your application runs:

An ApplicationStartingEvent is sent at the start of a run but before any processing except the registration of listeners and initializers.
An ApplicationEnvironmentPreparedEvent is sent when the Environment to be used in the context is known but before the context is created.
An ApplicationPreparedEvent is sent just before the refresh is started but after bean definitions have been loaded.
An ApplicationReadyEvent is sent after the refresh and any related callbacks have been processed, to indicate that the application is ready to service requests.
An ApplicationFailedEvent is sent if there is an exception on startup.

	Tip
	You often need not use application events, but it can be handy to know that they exist. Internally, Spring Boot uses events to handle a variety of tasks.

Application events are sent by using Spring Framework’s event publishing mechanism. Part of this mechanism ensures that an event published to the listeners in a child context is also published to the listeners in any ancestors contexts. As a result of this, if your application uses a hierarchy of SpringApplication instances, a listener may receive multiple instances of the same type of application event.

To allow your listener to distinguish between an event for its context and an event for a descendant context, it should request that its application context is injected and then compare the injected context with the context of the event. The context can be injected by implementing ApplicationContextAware or, if the listener is a bean, by using @Autowired .

23.6 Web Environment

A SpringApplication attempts to create the right type of ApplicationContext on your behalf. By default, an AnnotationConfigApplicationContext or AnnotationConfigServletWebServerApplicationContext is used, depending on whether you are developing a web application or not.

The algorithm used to determine a ‘web environment’ is fairly simplistic (it is based on the presence of a few classes). You can use setWebEnvironment(boolean webEnvironment) if you need to override the default.

It is also possible to take complete control of the ApplicationContext type that is used by calling setApplicationContextClass(…) .

	Tip
	It is often desirable to call `setWebEnvironment(false)` when using `SpringApplication` within a JUnit test.

23.7 Accessing Application Arguments

If you need to access the application arguments that were passed to SpringApplication.run(…) , you can inject a org.springframework.boot.ApplicationArguments bean. The ApplicationArguments interface provides access to both the raw String[] arguments as well as parsed option and non-option arguments, as shown in the following example:

import org.springframework.boot.*
import org.springframework.beans.factory.annotation.*
import org.springframework.stereotype.*
@Component
public class MyBean {
	@Autowired
	public MyBean(ApplicationArguments args) {
		boolean debug = args.containsOption("debug");
		List<String> files = args.getNonOptionArgs();
		// if run with "--debug logfile.txt" debug=true, files=["logfile.txt"]
}

	Tip
	Spring Boot also registers a `CommandLinePropertySource` with the Spring `Environment` . This allows you to also inject single application arguments by using the `@Value` annotation.

23.8 Using the ApplicationRunner or CommandLineRunner

If you need to run some specific code once the SpringApplication has started, you can implement the ApplicationRunner or CommandLineRunner interfaces. Both interfaces work in the same way and offer a single run method, which is called just before SpringApplication.run(…) completes.

The CommandLineRunner interfaces provides access to application arguments as a simple string array, whereas the ApplicationRunner uses the ApplicationArguments interface discussed earlier.

import org.springframework.boot.*
import org.springframework.stereotype.*
@Component
public class MyBean implements CommandLineRunner {
	public void run(String... args) {
		// Do something...
}

You can additionally implement the org.springframework.core.Ordered interface or use the org.springframework.core.annotation.Order annotation if several CommandLineRunner or ApplicationRunner beans are defined that must be called in a specific order.

23.9 Application Exit

Each SpringApplication registers a shutdown hook with the JVM to ensure that the ApplicationContext closes gracefully on exit. All the standard Spring lifecycle callbacks (such as the DisposableBean interface or the @PreDestroy annotation) can be used.

In addition, beans may implement the org.springframework.boot.ExitCodeGenerator interface if they wish to return a specific exit code when SpringApplication.exit() is called. This exit code can then be passed to System.exit() to return it as a status code, as shown in the following example:

@SpringBootApplication
public class ExitCodeApplication {
	@Bean
	public ExitCodeGenerator exitCodeGenerator() {
		return () -> 42;
	public static void main(String[] args) {
		System.exit(SpringApplication
				.exit(SpringApplication.run(ExitCodeApplication.class, args)));
}

Also, the ExitCodeGenerator interface may be implemented by exceptions. When such an exception is encountered, Spring Boot returns the exit code provided by the implemented getExitCode() method.

23.10 Admin Features

It is possible to enable admin-related features for the application by specifying the spring.application.admin.enabled property. This exposes the SpringApplicationAdminMXBean on the platform MBeanServer . You could use this feature to administer your Spring Boot application remotely. This feature could also be useful for any service wrapper implementation.

	Tip
	If you want to know on which HTTP port the application is running, get the property with a key of `local.server.port` .

	Caution
	Take care when enabling this feature, as the MBean exposes a method to shutdown the application.

24. Externalized Configuration

Spring Boot lets you externalize your configuration so that you can work with the same application code in different environments. You can use properties files, YAML files, environment variables, and command-line arguments to externalize configuration. Property values can be injected directly into your beans by using the @Value annotation, accessed through Spring’s Environment abstraction or bound to structured objects through @ConfigurationProperties .

Spring Boot uses a very particular PropertySource order that is designed to allow sensible overriding of values. Properties are considered in the following order:

Devtools global settings properties on your home directory ( ~/.spring-boot-devtools.properties when devtools is active).
@TestPropertySource annotations on your tests.
@SpringBootTest#properties annotation attribute on your tests.
Command line arguments.
Properties from SPRING_APPLICATION_JSON (inline JSON embedded in an environment variable or system property).
ServletConfig init parameters.
ServletContext init parameters.
JNDI attributes from java:comp/env .
Java System properties ( System.getProperties() ).
OS environment variables.
A RandomValuePropertySource that only has properties in random.* .
Profile-specific application properties outside of your packaged jar ( application-{profile}.properties and YAML variants).
Profile-specific application properties packaged inside your jar ( application-{profile}.properties and YAML variants).
Application properties outside of your packaged jar ( application.properties and YAML variants).
Application properties packaged inside your jar ( application.properties and YAML variants).
@PropertySource annotations on your @Configuration classes.
Default properties (specified using SpringApplication.setDefaultProperties ).

To provide a concrete example, suppose you develop a @Component that uses a name property, as shown in the following example:

import org.springframework.stereotype.*
import org.springframework.beans.factory.annotation.*
@Component
public class MyBean {
    @Value("${name}")
    private String name;
    // ...
}

On your application classpath (for example, inside your jar) you can have an application.properties file that provides a sensible default property value for name . When running in a new environment, an application.properties file can be provided outside of your jar that overrides the name . For one-off testing, you can launch with a specific command line switch (for example, java -jar app.jar --name="Spring" ).

Tip

The SPRING_APPLICATION_JSON properties can be supplied on the command line with an environment variable. For example, you could use the following line in a UN*X shell:

$ SPRING_APPLICATION_JSON='{"foo":{"bar":"spam"}}' java -jar myapp.jar

In the preceding example, you end up with foo.bar=spam in the Spring Environment . You can also supply the JSON as spring.application.json in a System property, as shown in the following example:

$ java -Dspring.application.json='{"foo":"bar"}' -jar myapp.jar

You can also supply the JSON by using a command line argument, as shown in the following example:

$ java -jar myapp.jar --spring.application.json='{"foo":"bar"}'

You can also supply the JSON as a JNDI variable, as follows: java:comp/env/spring.application.json .

24.1 Configuring Random Values

The RandomValuePropertySource is useful for injecting random values (for example, into secrets or test cases). It can produce integers, longs, uuids or strings, as shown in the following example:

my.secret=${random.value}
my.number=${random.int}
my.bignumber=${random.long}
my.uuid=${random.uuid}
my.number.less.than.ten=${random.int(10)}
my.number.in.range=${random.int[1024,65536]}

The random.int* syntax is OPEN value (,max) CLOSE where the OPEN,CLOSE are any character and value,max are integers. If max is provided, then value is the minimum value and max is the maximum value (exclusive).

24.2 Accessing Command Line Properties

By default, SpringApplication converts any command line option arguments (that is, arguments starting with ‘--’, such as --server.port=9000 ) to a property and add it to the Spring Environment . As mentioned previously, command line properties always take precedence over other property sources.

If you do not want command line properties to be added to the Environment , you can disable them by using SpringApplication.setAddCommandLineProperties(false) .

24.3 Application Property Files

SpringApplication loads properties from application.properties files in the following locations and adds them to the Spring Environment :

A /config subdirectory of the current directory.
The current directory
A classpath /config package
The classpath root

The list is ordered by precedence (properties defined in locations higher in the list override those defined in lower locations).

	Note
	You can also use YAML ('.yml') files as an alternative to '.properties'.

If you do not like application.properties as the configuration file name, you can switch to another file name by specifying a spring.config.name environment property. You can also refer to an explicit location by using the spring.config.location environment property (a comma-separated list of directory locations or file paths). The following example shows how to specify a different file name:

$ java -jar myproject.jar --spring.config.name=myproject

The following example shows how to specify two locations:

$ java -jar myproject.jar --spring.config.location=classpath:/default.properties,classpath:/override.properties

	Warning
	`spring.config.name` and `spring.config.location` are used very early to determine which files have to be loaded, so they must be defined as an environment property (typically an OS environment variable, a system property, or a command line argument).

If spring.config.location contains directories (as opposed to files), they should end in / (and, at runtime, be appended with the names generated from spring.config.name before being loaded, including profile-specific file names). Files specified in spring.config.location are used as-is, with no support for profile-specific variants, and are overridden by any profile-specific properties.

Config locations are searched in reverse order. By default, the configured locations are classpath:/,classpath:/config/,file:./,file:./config/ . The resulting search order is the following:

file:./config/
file:./
classpath:/config/
classpath:/

When custom config locations are configured using spring.config.location , they replace the default locations. For example, if spring.config.location is configured with the value classpath:/custom-config/,file:./custom-config/ , the search order becomes the following:

file:./custom-config/
classpath:custom-config/

Alternatively, when custom config locations are configured by using spring.config.addition-location , they are used in addition to the default locations. Additional locations are searched before the default locations. For example, if additional locations of classpath:/custom-config/,file:./custom-config/ are configured, the search order becomes the following:

file:./custom-config/
classpath:custom-config/
file:./config/
file:./
classpath:/config/
classpath:/

This search ordering lets you specify default values in one configuration file and then selectively override those values in another. You can provide default values for your application in application.properties (or whatever other basename you choose with spring.config.name ) in one of the default locations. These default values can then be overriden at runtime with a different file located in one of the custom locations.

	Note
	If you use environment variables rather than system properties, most operating systems disallow period-separated key names, but you can use underscores instead (for example, `SPRING_CONFIG_NAME` instead of `spring.config.name` ).

	Note
	If your application runs in a container, then JNDI properties (in `java:comp/env` ) or servlet context initialization parameters can be used instead of, or as well as, environment variables or system properties.

24.4 Profile-specific Properties

In addition to application.properties files, profile-specific properties can also be defined by using the naming convention application-{profile}.properties . The Environment has a set of default profiles (by default [default] ) that are used if no active profiles are set. In other words, if no profiles are explicitly activated, then properties from application-default.properties are loaded.

Profile-specific properties are loaded from the same locations as standard application.properties , with profile-specific files always overriding the non-specific ones, irrespective of whether the profile-specific files are inside or outside your packaged jar.

If several profiles are specified, a last-wins strategy applies. For example, profiles specified by the spring.profiles.active property are added after those configured through the SpringApplication API and therefore take precedence.

	Note
	If you have specified any files in `spring.config.location` , profile-specific variants of those files are not considered. Use directories in `spring.config.location` if you want to also use profile-specific properties.

24.5 Placeholders in Properties

The values in application.properties are filtered through the existing Environment when they are used, so you can refer back to previously defined values (for example, from System properties).

app.name=MyApp
app.description=${app.name} is a Spring Boot application

	Tip
	You can also use this technique to create ‘short’ variants of existing Spring Boot properties. See the Section 73.4, “Use ‘Short’ Command Line Arguments” how-to for details.

24.6 Using YAML Instead of Properties

YAML is a superset of JSON and, as such, is a very convenient format for specifying hierarchical configuration data. The SpringApplication class automatically supports YAML as an alternative to properties whenever you have the SnakeYAML library on your classpath.

	Note
	If you use ‘Starters’, SnakeYAML is automatically provided by `spring-boot-starter` .

24.6.1 Loading YAML

Spring Framework provides two convenient classes that can be used to load YAML documents. The YamlPropertiesFactoryBean loads YAML as Properties and the YamlMapFactoryBean loads YAML as a Map .

For example, consider the following YAML document:

environments:
	dev:
		url: http://dev.bar.com
		name: Developer Setup
	prod:
		url: http://foo.bar.com
		name: My Cool App

The preceding example would be transformed into the following properties:

environments.dev.url=http://dev.bar.com
environments.dev.name=Developer Setup
environments.prod.url=http://foo.bar.com
environments.prod.name=My Cool App

YAML lists are represented as property keys with [index] dereferencers. For example, consider the following YAML:

my:
servers:
	- dev.bar.com
	- foo.bar.com

The preceding example would be transformed into these properties:

my.servers[0]=dev.bar.com
my.servers[1]=foo.bar.com

To bind to properties like that by using the Spring DataBinder utilities (which is what @ConfigurationProperties does), you need to have a property in the target bean of type java.util.List (or Set ) and you either need to provide a setter or initialize it with a mutable value. For example, the following example binds to the properties shown previously:

@ConfigurationProperties(prefix="my")
public class Config {
	private List<String> servers = new ArrayList<String>();
	public List<String> getServers() {
		return this.servers;
}

	Note
	When lists are configured in more than one place, overriding works by replacing the entire list. In the preceding example, when `my.servers` is redefined in several places, the entire list from the `PropertySource` with higher precedence will override any other configuration for that list. Both comma-separated lists and yaml lists can be used for completely overriding the contents of the list.

24.6.2 Exposing YAML as Properties in the Spring Environment

The YamlPropertySourceLoader class can be used to expose YAML as a PropertySource in the Spring Environment . Doing so lets you use the @Value annotation with placeholders syntax to access YAML properties.

24.6.3 Multi-profile YAML Documents

You can specify multiple profile-specific YAML documents in a single file by using a spring.profiles key to indicate when the document applies, as shown in the following example:

server:
	address: 192.168.1.100
spring:
	profiles: development
server:
	address: 127.0.0.1
spring:
	profiles: production
server:
	address: 192.168.1.120

In the preceding example, if the development profile is active, the server.address property is 127.0.0.1 . Similarly, if the production profile is active, the server.address property is 192.168.1.120 . If the development and production profiles are not enabled, then the value for the property is 192.168.1.100 .

If none are explicitly active when the application context starts, the default profiles are activated . So, in the following YAML, we set a value for security.user.password that is only available in the "default" profile:

server:
  port: 8000
spring:
  profiles: default
security:
  user:
    password: weak

Whereas, in the following example, the password is always set because it is not attached to any profile, and it would have to be explicitly reset in all other profiles as necessary:

server:
  port: 8000
security:
  user:
    password: weak

Spring profiles designated by using the "spring.profiles" element may optionally be negated by using the ! character. If both negated and non-negated profiles are specified for a single document, at least one non-negated profile must match, and no negated profiles may match.

24.6.4 YAML Shortcomings

YAML files cannot be loaded by using the @PropertySource annotation. So, in the case that you need to load values that way, you need to use a properties file.

24.6.5 Merging YAML Lists

As we have seen above , any YAML content is ultimately transformed to properties. That process may be counter-intuitive when overriding “list” properties through a profile.

For example, assume a MyPojo object with name and description attributes that are null by default. The following example exposes a list of MyPojo from FooProperties :

@ConfigurationProperties("foo")
public class FooProperties {
	private final List<MyPojo> list = new ArrayList<>();
	public List<MyPojo> getList() {
		return this.list;
}

Consider the following configuration:

foo:
  list:
    - name: my name
      description: my description
spring:
  profiles: dev
foo:
  list:
       - name: my another name

If the dev profile is not active, FooProperties.list contains one MyPojo entry as defined above. If the dev profile is enabled however, the list still contains only one entry (with a name of “my another name” and a description of null ). This configuration does not add a second MyPojo instance to the list, and it does not merge the items.

When a collection is specified in multiple profiles, the one with the highest priority (and only that one) is used:

foo:
  list:
	- name: my name
	  description: my description
	- name: another name
	  description: another description
spring:
  profiles: dev
foo:
  list:
	 - name: my another name

In the preceding example, if the dev profile is active, FooProperties.list contains one MyPojo entry (with a name of “my another name” and a description of null ).

24.7 Type-safe Configuration Properties

Using the @Value("${property}") annotation to inject configuration properties can sometimes be cumbersome, especially if you are working with multiple properties or your data is hierarchical in nature. Spring Boot provides an alternative method of working with properties that lets strongly typed beans govern and validate the configuration of your application, as shown in the following example:

package com.example;
import java.net.InetAddress;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.springframework.boot.context.properties.ConfigurationProperties;
@ConfigurationProperties("foo")
public class FooProperties {
	private boolean enabled;
	private InetAddress remoteAddress;
	private final Security security = new Security();
	public boolean isEnabled() { ... }
	public void setEnabled(boolean enabled) { ... }
	public InetAddress getRemoteAddress() { ... }
	public void setRemoteAddress(InetAddress remoteAddress) { ... }
	public Security getSecurity() { ... }
	public static class Security {
		private String username;
		private String password;
		private List<String> roles = new ArrayList<>(Collections.singleton("USER"));
		public String getUsername() { ... }
		public void setUsername(String username) { ... }
		public String getPassword() { ... }
		public void setPassword(String password) { ... }
		public List<String> getRoles() { ... }
		public void setRoles(List<String> roles) { ... }
}

The preceding POJO defines the following properties:

foo.enabled , false by default.
foo.remote-address , with a type that can be coerced from String .
foo.security.username , with a nested "security" object whose name is determined by the name of the property. In particular, the return type is not used at all there and could have been SecurityProperties .
foo.security.password .
foo.security.roles , with a collection of String .

Note

Getters and setters are usually mandatory, since binding is through standard Java Beans property descriptors, just like in Spring MVC. A setter may be omitted in the following cases:

Maps, as long as they are initialized, need a getter but not necessarily a setter, since they can be mutated by the binder.
Collections and arrays can be accessed either through an index (typically with YAML) or by using a single comma-separated value (properties). In the latter case, a setter is mandatory. We recommend to always add a setter for such types. If you initialize a collection, make sure it is not immutable (as in the preceding example).
If nested POJO properties are initialized (like the Security field in the preceding example), a setter is not required. If you want the binder to create the instance on the fly by using its default constructor, you need a setter.

Some people use Project Lombok to add getters and setters automatically. Make sure that Lombok does not generate any particular constructor for such type, as it is used automatically by the container to instantiate the object.

	Tip
	See also the differences between `@Value` and `@ConfigurationProperties` .

You also need to list the properties classes to register in the @EnableConfigurationProperties annotation:

@Configuration
@EnableConfigurationProperties(FooProperties.class)
public class MyConfiguration {
}

Note

When the @ConfigurationProperties bean is registered that way, the bean has a conventional name: <prefix>-<fqn> , where <prefix> is the environment key prefix specified in the @ConfigurationProperties annotation and <fqn> the fully qualified name of the bean. If the annotation does not provide any prefix, only the fully qualified name of the bean is used.

The bean name in the example above is foo-com.example.FooProperties .

Even if the preceding configuration creates a regular bean for FooProperties , we recommend that @ConfigurationProperties only deal with the environment and, in particular, does not inject other beans from the context. Having said that, the @EnableConfigurationProperties annotation is also automatically applied to your project so that any existing bean annotated with @ConfigurationProperties is configured from the Environment . You could shortcut MyConfiguration by making sure FooProperties is already a bean, as shown in the following example:

@Component
@ConfigurationProperties(prefix="foo")
public class FooProperties {
	// ... see the preceding example
}

This style of configuration works particularly well with the SpringApplication external YAML configuration, as shown in the following example:

# application.yml
foo:
	remote-address: 192.168.1.1
	security:
		username: foo
		roles:
		  - USER
		  - ADMIN
# additional configuration as required

To work with @ConfigurationProperties beans, you can just inject them in the same way as any other bean, as shown in the following example:

@Service
public class MyService {
	private final FooProperties properties;
	@Autowired
	public MyService(FooProperties properties) {
	    this.properties = properties;
 	//...
	@PostConstruct
	public void openConnection() {
		Server server = new Server(this.properties.getRemoteAddress());
		// ...
}

	Tip
	Using `@ConfigurationProperties` also lets you generate metadata files that can be used by IDEs to offer auto-completion for your own keys. See the Appendix B, Configuration Metadata appendix for details.

24.7.1 Third-party Configuration

As well as using @ConfigurationProperties to annotate a class, you can also use it on public @Bean methods. Doing so can be particularly useful when you want to bind properties to third-party components that are outside of your control.

To configure a bean from the Environment properties, add @ConfigurationProperties to its bean registration, as shown in the following example:

@ConfigurationProperties(prefix = "bar")
@Bean
public BarComponent barComponent() {
}

Any property defined with the bar prefix is mapped onto that BarComponent bean in a similar manner as the preceding FooProperties example.

24.7.2 Relaxed Binding

Spring Boot uses some relaxed rules for binding Environment properties to @ConfigurationProperties beans, so there does not need to be an exact match between the Environment property name and the bean property name. Common examples where this is useful include dash-separated environment properties (for example, context-path binds to contextPath ), and capitalized environment properties (for example, PORT binds to port ).

For example, consider the following @ConfigurationProperties class:

@ConfigurationProperties(prefix="acme.my-project.person")
public class OwnerProperties {
	private String firstName;
	public String getFirstName() {
		return this.firstName;
	public void setFirstName(String firstName) {
		this.firstName = firstName;
}

In the preceding example, the following properties names can all be used:

Table 24.1. relaxed binding

Property	Note
`acme.my-project.person.firstName`	Standard camel case syntax.
`acme.my-project.person.first-name`	Kebab case, which is recommended for use in `.properties` and `.yml` files.
`acme.my-project.person.first_name`	Underscore notation, which is an alternative format for use in `.properties` and `.yml` files.
`ACME_MYPROJECT_PERSON_FIRSTNAME`	Upper case format, which is recommended when using a system environment variables.

	Note
	The `prefix` value for the annotation must be in kebab case (lowercase and separated by `-` , i.e. `acme.my-project.person` ).

Table 24.2. relaxed binding rules per property source

Property Source	Simple	List
Properties Files	Camel case, kebab case, or underscore notation	Standard list syntax using `[ ]` or comma-separated values
YAML Files	Camel case, kebab case, or underscore notation	Standard YAML list syntax or comma-separated values
Environment Variables	Upper case format with underscore as the delimiter. `_` should not be used within a property name	Numeric values surrounded by underscores, such as `MY_FOO_1_BAR = my.foo[1].bar`
System properties	Camel case, kebab case, or underscore notation	Standard list syntax using `[ ]` or comma-separated values

	Tip
	We recommend that, when possible, properties are stored in lower-case kebab format, such as `my.property-name=foo` .

24.7.3 Properties Conversion

Spring attempts to coerce the external application properties to the right type when it binds to the @ConfigurationProperties beans. If you need custom type conversion, you can provide a ConversionService bean (with bean named conversionService ) or custom property editors (through a CustomEditorConfigurer bean) or custom Converters (with bean definitions annotated as @ConfigurationPropertiesBinding ).

Note

As this bean is requested very early during the application lifecycle, make sure to limit the dependencies that your ConversionService is using. Typically, any dependency that you require may not be fully initialized at creation time. You may want to rename your custom ConversionService if it is not required for configuration keys coercion and only rely on custom converters qualified with @ConfigurationPropertiesBinding .

24.7.4 @ConfigurationProperties Validation

Spring Boot attempts to validate @ConfigurationProperties classes whenever they are annotated with Spring’s @Validated annotation. You can use JSR-303 javax.validation constraint annotations directly on your configuration class. To do so, ensure that a compliant JSR-303 implementation is on your classpath and then add constraint annotations to your fields, as shown in the following example:

@ConfigurationProperties(prefix="foo")
@Validated
public class FooProperties {
	@NotNull
	private InetAddress remoteAddress;
	// ... getters and setters
}

In order to validate the values of nested properties, you must annotate the associated field as @Valid to trigger its validation. The following example builds on the preceding FooProperties example:

@ConfigurationProperties(prefix="connection")
@Validated
public class FooProperties {
	@NotNull
	private InetAddress remoteAddress;
	@Valid
	private final Security security = new Security();
	// ... getters and setters
	public static class Security {
		@NotEmpty
		public String username;
		// ... getters and setters
}

You can also add a custom Spring Validator by creating a bean definition called configurationPropertiesValidator . The @Bean method should be declared static . The configuration properties validator is created very early in the application’s lifecycle, and declaring the @Bean method as static lets the bean be created without having to instantiate the @Configuration class. Doing so avoids any problems that may be caused by early instantiation. There is a property validation sample that shows how to set things up.

	Tip
	The `spring-boot-actuator` module includes an endpoint that exposes all `@ConfigurationProperties` beans. Point your web browser to `/actuator/configprops` or use the equivalent JMX endpoint. See the " Production ready features " section for details.

24.7.5 @ConfigurationProperties vs. @Value

The @Value annotation is a core container feature, and it does not provide the same features as type-safe configuration properties. The following table summarizes the features that are supported by @ConfigurationProperties and @Value :

Feature	`@ConfigurationProperties`	`@Value`
Relaxed binding	Yes	No
Meta-data support	Yes	No
`SpEL` evaluation	No	Yes

If you define a set of configuration keys for your own components, we recommend you to group them in a POJO annotated with @ConfigurationProperties . You should also be aware that, since @Value does not support relaxed binding, it is not a good candidate if you need to provide the value by using environment variables.

Finally, while you can write a SpEL expression in @Value , such expressions are not processed from Application property files .

25. Profiles

Spring Profiles provide a way to segregate parts of your application configuration and make it be available only in certain environments. Any @Component or @Configuration can be marked with @Profile to limit when it is loaded, as shown in the following example:

@Configuration
@Profile("production")
public class ProductionConfiguration {
	// ...
}

In the normal Spring way, you can use a spring.profiles.active Environment property to specify which profiles are active. You can specify the property in any of the usual ways. For example, you could include it in your application.properties :

spring.profiles.active=dev,hsqldb

You could also specify it on the command line by using the following switch: --spring.profiles.active=dev,hsqldb .

25.1 Adding Active Profiles

The spring.profiles.active property follows the same ordering rules as other properties: The highest PropertySource wins. This means that you can specify active profiles in application.properties and then replace them by using the command line switch.

Sometimes, it is useful to have profile-specific properties that add to the active profiles rather than replace them. The spring.profiles.include property can be used to unconditionally add active profiles. The SpringApplication entry point also has a Java API for setting additional profiles (that is, on top of those activated by the spring.profiles.active property). See the setAdditionalProfiles() method.

For example, when an application with the following properties is run by using the switch, --spring.profiles.active=prod , the proddb and prodmq profiles are also activated:

---
my.property: fromyamlfile
spring.profiles: prod
spring.profiles.include:
  - proddb
  - prodmq

	Note
	Remember that the `spring.profiles` property can be defined in a YAML document to determine when this particular document is included in the configuration. See Section 73.7, “Change Configuration Depending on the Environment” for more details.

25.2 Programmatically Setting Profiles

You can programmatically set active profiles by calling SpringApplication.setAdditionalProfiles(…) before your application runs. It is also possible to activate profiles by using Spring’s ConfigurableEnvironment interface.

25.3 Profile-specific Configuration Files

Profile-specific variants of both application.properties (or application.yml ) and files referenced through @ConfigurationProperties are considered as files are loaded. See Section 24.4, “Profile-specific Properties” for details.

26. Logging

Spring Boot uses Commons Logging for all internal logging but leaves the underlying log implementation open. Default configurations are provided for Java Util Logging , Log4J2 , and Logback . In each case, loggers are pre-configured to use console output with optional file output also available.

By default, if you use the ‘Starters’, Logback is used for logging. Appropriate Logback routing is also included to ensure that dependent libraries that use Java Util Logging, Commons Logging, Log4J, or SLF4J all work correctly.

	Tip
	There are a lot of logging frameworks available for Java. Do not worry if the above list seems confusing. Generally, you do not need to change your logging dependencies and the Spring Boot defaults work just fine.

26.1 Log Format

The default log output from Spring Boot resembles the following example:

2014-03-05 10:57:51.112  INFO 45469 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet Engine: Apache Tomcat/7.0.52
2014-03-05 10:57:51.253  INFO 45469 --- [ost-startStop-1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2014-03-05 10:57:51.253  INFO 45469 --- [ost-startStop-1] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 1358 ms
2014-03-05 10:57:51.698  INFO 45469 --- [ost-startStop-1] o.s.b.c.e.ServletRegistrationBean        : Mapping servlet: 'dispatcherServlet' to [/]
2014-03-05 10:57:51.702  INFO 45469 --- [ost-startStop-1] o.s.b.c.embedded.FilterRegistrationBean  : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]

The following items are output:

Date and Time — Millisecond precision and easily sortable.
Log Level — ERROR , WARN , INFO , DEBUG , or TRACE .
Process ID.
A --- separator to distinguish the start of actual log messages.
Thread name — Enclosed in square brackets (may be truncated for console output).
Logger name — This is usually the source class name (often abbreviated).
The log message.

	Note
	Logback does not have a `FATAL` level. It is mapped to `ERROR` .

26.2 Console Output

The default log configuration echoes messages to the console as they are written. By default, ERROR -level, WARN -level, and INFO -level messages are logged. You can also enable a “debug” mode by starting your application with a --debug flag.

$ java -jar myapp.jar --debug

	Note
	You can also specify `debug=true` in your `application.properties` .

When the debug mode is enabled, a selection of core loggers (embedded container, Hibernate, and Spring Boot) are configured to output more information. Enabling the debug mode does not configure your application to log all messages with DEBUG level.

Alternatively, you can enable a “trace” mode by starting your application with a --trace flag (or trace=true in your application.properties ). Doing so enables trace logging for a selection of core loggers (embedded container, Hibernate schema generation, and the whole Spring portfolio).

26.2.1 Color-coded Output

If your terminal supports ANSI, color output is used to aid readability. You can set spring.output.ansi.enabled to a supported value to override the auto detection.

Color coding is configured by using the %clr conversion word. In its simplest form the converter colors the output according to the log level, as shown in the following example:

%clr(%5p)

The mapping of log level to a color is as follows:

Level	Color
`FATAL`	Red
`ERROR`	Red
`WARN`	Yellow
`INFO`	Green
`DEBUG`	Green
`TRACE`	Green

Alternatively, you can specify the color or style that should be used by providing it as an option to the conversion. For example, to make the text yellow, use the following setting:

%clr(%d{yyyy-MM-dd HH:mm:ss.SSS}){yellow}

The following colors and styles are supported:

blue
cyan
faint
green
magenta
red
yellow

26.3 File Output

By default, Spring Boot logs only to the console and does not write log files. If you want to write log files in addition to the console output, you need to set a logging.file or logging.path property (for example, in your application.properties ).

The following table shows how the logging.* properties can be used together:

Table 26.1. Logging properties

`logging.file`	`logging.path`	Example	Description
(none)	(none)		Console only logging.
Specific file	(none)	`my.log`	Writes to the specified log file. Names can be an exact location or relative to the current directory.
(none)	Specific directory	`/var/log`	Writes `spring.log` to the specified directory. Names can be an exact location or relative to the current directory.

Log files rotate when they reach 10 MB and, as with console output, ERROR -level, WARN -level, and INFO -level messages are logged by default. Size limits can be changed using the logging.file.max-size property. Previously rotated files are archived indefinitely unless the logging.file.max-history property has been set.

	Note
	The logging system is initialized early in the application lifecycle. Consequently, logging properties are not found in property files loaded through `@PropertySource` annotations.

	Tip
	Logging properties are independent of the actual logging infrastructure. As a result, specific configuration keys (such as `logback.configurationFile` for Logback) are not managed by spring Boot.

26.4 Log Levels

All the supported logging systems can have the logger levels set in the Spring Environment (for example, in application.properties ) by using ‘logging.level.*=LEVEL’ where ‘LEVEL’ is one of TRACE, DEBUG, INFO, WARN, ERROR, FATAL, or OFF. The root logger can be configured by using logging.level.root . The following example shows potential logging settings in application.properties :

logging.level.root=WARN
logging.level.org.springframework.web=DEBUG
logging.level.org.hibernate=ERROR

26.5 Custom Log Configuration

The various logging systems can be activated by including the appropriate libraries on the classpath and can be further customized by providing a suitable configuration file in the root of the classpath or in a location specified by the Spring Environment property logging.config .

You can force Spring Boot to use a particular logging system by using the org.springframework.boot.logging.LoggingSystem system property. The value should be the fully qualified class name of a LoggingSystem implementation. You can also disable Spring Boot’s logging configuration entirely by using a value of none .

	Note
	Since logging is initialized before the `ApplicationContext` is created, it is not possible to control logging from `@PropertySources` in Spring `@Configuration` files. System properties and the conventional Spring Boot external configuration files work fine.)

Depending on your logging system, the following files are loaded:

Logging System	Customization
Logback	`logback-spring.xml` , `logback-spring.groovy` , `logback.xml` , or `logback.groovy`
Log4j2	`log4j2-spring.xml` or `log4j2.xml`
JDK (Java Util Logging)	`logging.properties`

	Note
	When possible, we recommend that you use the `-spring` variants for your logging configuration (for example, `logback-spring.xml` rather than `logback.xml` ). If you use standard configuration locations, Spring cannot completely control log initialization.

	Warning
	There are known classloading issues with Java Util Logging that cause problems when running from an 'executable jar'. We recommend that you avoid it when running from an 'executable jar' if at all possible.

To help with the customization, some other properties are transferred from the Spring Environment to System properties, as described in the following table:

Spring Environment	System Property	Comments
`logging.exception-conversion-word`	`LOG_EXCEPTION_CONVERSION_WORD`	The conversion word used when logging exceptions.
`logging.file`	`LOG_FILE`	If defined, it is used in the default log configuration.
`logging.file.max-size`	`LOG_FILE_MAX_SIZE`	Maximum log file size (if LOG_FILE enabled). (Only supported with the default logback setup.)
`logging.file.max-history`	`LOG_FILE_MAX_HISTORY`	Maximum number of archive log files to keep (if LOG_FILE enabled). (Only supported with the default logback setup.)
`logging.path`	`LOG_PATH`	If defined, it is used in the default log configuration.
`logging.pattern.console`	`CONSOLE_LOG_PATTERN`	The log pattern to use on the console (stdout). (Only supported with the default logback setup.)
`logging.pattern.file`	`FILE_LOG_PATTERN`	The log pattern to use in a file (if `LOG_FILE` is enabled). (Only supported with the default logback setup.)
`logging.pattern.level`	`LOG_LEVEL_PATTERN`	The format to use when rendering the log level (default `%5p` ). (Only supported with the default logback setup.)
`PID`	`PID`	The current process ID (discovered if possible and when not already defined as an OS environment variable).

All the supported logging systems can consult System properties when parsing their configuration files. See the default configurations in spring-boot.jar for examples:

	Tip
	If you want to use a placeholder in a logging property, you should use Spring Boot’s syntax and not the syntax of the underlying framework. Notably, if you use Logback, you should use `:` as the delimiter between a property name and its default value and not use `:-` .

Tip

You can add MDC and other ad-hoc content to log lines by overriding only the LOG_LEVEL_PATTERN (or logging.pattern.level with Logback). For example, if you use logging.pattern.level=user:%X{user} %5p , then the default log format contains an MDC entry for "user", if it exists, as shown in the following example.

2015-09-30 12:30:04.031 user:someone INFO 22174 --- [  nio-8080-exec-0] demo.Controller
Handling authenticated request

26.6 Logback Extensions

Spring Boot includes a number of extensions to Logback that can help with advanced configuration. You can use these extensions in your logback-spring.xml configuration file.

	Note
	Because the standard `logback.xml` configuration file is loaded too early, you cannot use extensions in it. You need to either use `logback-spring.xml` or define a `logging.config` property.

	Warning
	The extensions cannot be used with Logback’s configuration scanning . If you attempt to do so, making changes to the configuration file results in an error similar to one of the following being logged:

ERROR in ch.qos.logback.core.joran.spi.Interpreter@4:71 - no applicable action for [springProperty], current ElementPath is [[configuration][springProperty]]
ERROR in ch.qos.logback.core.joran.spi.Interpreter@4:71 - no applicable action for [springProfile], current ElementPath is [[configuration][springProfile]]

26.6.1 Profile-specific Configuration

The <springProfile> tag lets you optionally include or exclude sections of configuration based on the active Spring profiles. Profile sections are supported anywhere within the <configuration> element. Use the name attribute to specify which profile accepts the configuration. Multiple profiles can be specified using a comma-separated list. The following listing shows three sample profiles:

<springProfile name="staging">
	<!-- configuration to be enabled when the "staging" profile is active -->
</springProfile>
<springProfile name="dev, staging">
	<!-- configuration to be enabled when the "dev" or "staging" profiles are active -->
</springProfile>
<springProfile name="!production">
	<!-- configuration to be enabled when the "production" profile is not active -->
</springProfile>

26.6.2 Environment Properties

The <springProperty> tag lets you expose properties from the Spring Environment for use within Logback. Doing so can be useful if you want to access values from your application.properties file in your Logback configuration. The tag works in a similar way to Logback’s standard <property> tag. However, rather than specifying a direct value , you specify the source of the property (from the Environment ). If you need to store the property somewhere other than in local scope, you can use the scope attribute. If you need a fallback value (in case the property is not set in the Environment ), you can use the defaultValue attribute.

<springProperty scope="context" name="fluentHost" source="myapp.fluentd.host"
		defaultValue="localhost"/>
<appender name="FLUENT" class="ch.qos.logback.more.appenders.DataFluentAppender">
	<remoteHost>${fluentHost}</remoteHost>
</appender>

	Note
	The `source` must be specified using kebab case (such as `my.property-name` ). However, properties can be added to the `Environment` by using the relaxed rules.

27. Developing Web Applications

Spring Boot is well suited for web application development. You can create a self-contained HTTP server by using embedded Tomcat, Jetty, Undertow, or Netty. Most web applications use the spring-boot-starter-web module to get up and running quickly. You can also choose to build reactive web applications by using the spring-boot-starter-webflux module.

If you have not yet developed a Spring Boot web application, you can follow the "Hello World!" example in the Getting started section.

27.1 The ‘Spring Web MVC Framework’

The Spring Web MVC framework (often referred to as simply ‘Spring MVC’) is a rich ‘model view controller’ web framework. Spring MVC lets you create special @Controller or @RestController beans to handle incoming HTTP requests. Methods in your controller are mapped to HTTP by using @RequestMapping annotations.

The following code shows a typical example @RestController to serve JSON data:

@RestController
@RequestMapping(value="/users")
public class MyRestController {
	@RequestMapping(value="/{user}", method=RequestMethod.GET)
	public User getUser(@PathVariable Long user) {
		// ...
	@RequestMapping(value="/{user}/customers", method=RequestMethod.GET)
	List<Customer> getUserCustomers(@PathVariable Long user) {
		// ...
	@RequestMapping(value="/{user}", method=RequestMethod.DELETE)
	public User deleteUser(@PathVariable Long user) {
		// ...
}

Spring MVC is part of the core Spring Framework, and detailed information is available in the reference documentation . There are also several guides that cover Spring MVC available at spring.io/guides .

27.1.1 Spring MVC Auto-configuration

Spring Boot provides auto-configuration for Spring MVC that works well with most applications.

The auto-configuration adds the following features on top of Spring’s defaults:

Inclusion of ContentNegotiatingViewResolver and BeanNameViewResolver beans.
Support for serving static resources, including support for WebJars (covered later in this document).
Automatic registration of Converter , GenericConverter , and Formatter beans.
Support for HttpMessageConverters (see below).
Automatic registration of MessageCodesResolver (covered later in this document).
Static index.html support.
Custom Favicon support (covered later in this document).
Automatic use of a ConfigurableWebBindingInitializer bean (covered later in this document).

If you want to keep Spring Boot MVC features and you want to add additional MVC configuration (interceptors, formatters, view controllers, and other features), you can add your own @Configuration class of type WebMvcConfigurer but without @EnableWebMvc . If you wish to provide custom instances of RequestMappingHandlerMapping , RequestMappingHandlerAdapter , or ExceptionHandlerExceptionResolver , you can declare a WebMvcRegistrationsAdapter instance to provide such components.

If you want to take complete control of Spring MVC, you can add your own @Configuration annotated with @EnableWebMvc .

27.1.2 HttpMessageConverters

Spring MVC uses the HttpMessageConverter interface to convert HTTP requests and responses. Sensible defaults are included out of the box. For example, objects can be automatically converted to JSON (by using the Jackson library) or XML (by using the Jackson XML extension, if available, or by using JAXB if the Jackson XML extension is not available). By default, strings are encoded in UTF-8 .

If you need to add or customize converters, you can use Spring Boot’s HttpMessageConverters class:

import org.springframework.boot.autoconfigure.web.HttpMessageConverters;
import org.springframework.context.annotation.*;
import org.springframework.http.converter.*;
@Configuration
public class MyConfiguration {
	@Bean
	public HttpMessageConverters customConverters() {
		HttpMessageConverter<?> additional = ...
		HttpMessageConverter<?> another = ...
		return new HttpMessageConverters(additional, another);
}

Any HttpMessageConverter bean that is present in the context is added to the list of converters. You can also override default converters in the same way.

27.1.3 Custom JSON Serializers and Deserializers

If you use Jackson to serialize and deserialize JSON data, you might want to write your own JsonSerializer and JsonDeserializer classes. Custom serializers are usually registered with Jackson through a module , but Spring Boot provides an alternative @JsonComponent annotation that makes it easier to directly register Spring Beans.

You can use the @JsonComponent annotation directly on JsonSerializer or JsonDeserializer implementations. You can also use it on classes that contains serializers/deserializers as inner-classes, as shown in the following example:

import java.io.*;
import com.fasterxml.jackson.core.*;
import com.fasterxml.jackson.databind.*;
import org.springframework.boot.jackson.*;
@JsonComponent
public class Example {
	public static class Serializer extends JsonSerializer<SomeObject> {
		// ...
	public static class Deserializer extends JsonDeserializer<SomeObject> {
		// ...
}

All @JsonComponent beans in the ApplicationContext are automatically registered with Jackson. Because @JsonComponent is meta-annotated with @Component , the usual component-scanning rules apply.

Spring Boot also provides JsonObjectSerializer and JsonObjectDeserializer base classes that provide useful alternatives to the standard Jackson versions when serializing objects. See JsonObjectSerializer and JsonObjectDeserializer in the Javadoc for details.

27.1.4 MessageCodesResolver

Spring MVC has a strategy for generating error codes for rendering error messages from binding errors: MessageCodesResolver . If you set the spring.mvc.message-codes-resolver.format property PREFIX_ERROR_CODE or POSTFIX_ERROR_CODE , Spring Boot creates one for you (see the enumeration in DefaultMessageCodesResolver.Format ).

27.1.5 Static Content

By default, Spring Boot serves static content from a directory called /static (or /public or /resources or /META-INF/resources ) in the classpath or from the root of the ServletContext . It uses the ResourceHttpRequestHandler from Spring MVC so that you can modify that behavior by adding your own WebMvcConfigurer and overriding the addResourceHandlers method.

In a stand-alone web application, the default servlet from the container is also enabled and acts as a fallback, serving content from the root of the ServletContext if Spring decides not to handle it. Most of the time, this will not happen (unless you modify the default MVC configuration) because Spring can always handle requests through the DispatcherServlet .

By default, resources are mapped on /** , but you can tune that with the spring.mvc.static-path-pattern property. For instance, relocating all resources to /resources/** can be achieved as follows:

spring.mvc.static-path-pattern=/resources/**

You can also customize the static resource locations by using the spring.resources.static-locations property (replacing the default values with a list of directory locations). The root Servlet context path "/" is automatically added as a location as well.

In addition to the ‘standard’ static resource locations mentioned earlier, a special case is made for Webjars content . Any resources with a path in /webjars/** are served from jar files if they are packaged in the Webjars format.

	Tip
	Do not use the `src/main/webapp` directory if your application is packaged as a jar. Although this directory is a common standard, it works only with war packaging, and it is silently ignored by most build tools if you generate a jar.

Spring Boot also supports the advanced resource handling features provided by Spring MVC, allowing use cases such as cache-busting static resources or using version agnostic URLs for Webjars.

To use version agnostic URLs for Webjars, add the webjars-locator dependency. Then declare your Webjar. Using jQuery as an example, adding "/webjars/jquery/dist/jquery.min.js" results in "/webjars/jquery/x.y.z/dist/jquery.min.js" . where x.y.z is the Webjar version.

	Note
	If you are using JBoss, you need to declare the `webjars-locator-jboss-vfs` dependency instead of the `webjars-locator` . Otherwise, all Webjars resolve as a `404` .

To use cache busting, the following configuration configures a cache busting solution for all static resources, effectively adding a content hash, such as <link href="/css/spring-2a2d595e6ed9a0b24f027f2b63b134d6.css"/> , in URLs:

spring.resources.chain.strategy.content.enabled=true
spring.resources.chain.strategy.content.paths=/**

	Note
	Links to resources are rewritten in templates at runtime, thanks to a `ResourceUrlEncodingFilter` that is auto-configured for Thymeleaf and FreeMarker. You should manually declare this filter when using JSPs. Other template engines are currently not automatically supported but can be with custom template macros/helpers and the use of `ResourceUrlProvider` .

When loading resources dynamically with, for example, a JavaScript module loader, renaming files is not an option. That is why other strategies are also supported and can be combined. A "fixed" strategy adds a static version string in the URL without changing the file name, as shown in the following example:

spring.resources.chain.strategy.content.enabled=true
spring.resources.chain.strategy.content.paths=/**
spring.resources.chain.strategy.fixed.enabled=true
spring.resources.chain.strategy.fixed.paths=/js/lib/
spring.resources.chain.strategy.fixed.version=v12

With this configuration, JavaScript modules located under "/js/lib/" use a fixed versioning strategy ( "/v12/js/lib/mymodule.js" ), while other resources still use the content one ( <link href="/css/spring-2a2d595e6ed9a0b24f027f2b63b134d6.css"/> ).

See ResourceProperties for more of the supported options.

	Tip
	This feature has been thoroughly described in a dedicated post and in Spring Framework’s reference documentation .

	Tip
	If possible, JSPs should be avoided. There are several known limitations when using them with embedded servlet containers.

When you use one of these templating engines with the default configuration, your templates are picked up automatically from src/main/resources/templates .

Tip

Depending on how you run your application, IntelliJ IDEA orders the classpath differently. Running your application in the IDE from its main method results in a different ordering than when you run your application by using Maven or Gradle or from its packaged jar. This can cause Spring Boot to fail to find the templates on the classpath. If you have this problem, you can reorder the classpath in the IDE to place the module’s classes and resources first. Alternatively, you can configure the template prefix to search every templates directory on the classpath, as follows: classpath*:/templates/ .

27.1.10 Error Handling

By default, Spring Boot provides an /error mapping that handles all errors in a sensible way, and it is registered as a ‘global’ error page in the servlet container. For machine clients, it produces a JSON response with details of the error, the HTTP status, and the exception message. For browser clients, there is a ‘whitelabel’ error view that renders the same data in HTML format (to customize it, add a View that resolves to ‘error’). To replace the default behavior completely, you can implement ErrorController and register a bean definition of that type or add a bean of type ErrorAttributes to use the existing mechanism but replace the contents.

Tip

The BasicErrorController can be used as a base class for a custom ErrorController . This is particularly useful if you want to add a handler for a new content type (the default is to handle text/html specifically and provide a fallback for everything else). To do so, extend BasicErrorController , add a public method with a @RequestMapping that has a produces attribute, and create a bean of your new type.

You can also define a class annotated with @ControllerAdvice to customize the JSON document to return for a particular controller and/or exception type, as shown in the following example:

@ControllerAdvice(basePackageClasses = FooController.class)
public class FooControllerAdvice extends ResponseEntityExceptionHandler {
	@ExceptionHandler(YourException.class)
	@ResponseBody
	ResponseEntity<?> handleControllerException(HttpServletRequest request, Throwable ex) {
		HttpStatus status = getStatus(request);
		return new ResponseEntity<>(new CustomErrorType(status.value(), ex.getMessage()), status);
	private HttpStatus getStatus(HttpServletRequest request) {
		Integer statusCode = (Integer) request.getAttribute("javax.servlet.error.status_code");
		if (statusCode == null) {
			return HttpStatus.INTERNAL_SERVER_ERROR;
		return HttpStatus.valueOf(statusCode);
}

In the preceding example, if YourException is thrown by a controller defined in the same package as FooController , a JSON representation of the CustomErrorType POJO is used instead of the ErrorAttributes representation.

Custom Error Pages

If you want to display a custom HTML error page for a given status code, you can add a file to an /error folder. Error pages can either be static HTML (that is, added under any of the static resource folders) or built by using templates. The name of the file should be the exact status code or a series mask.

For example, to map 404 to a static HTML file, your folder structure would be as follows:

src/
 +- main/
     +- java/
     |   + <source code>
     +- resources/
         +- public/
             +- error/
             |   +- 404.html
             +- <other public assets>

To map all 5xx errors by using a FreeMarker template, your folder structure would be as follows:

src/
 +- main/
     +- java/
     |   + <source code>
     +- resources/
         +- templates/
             +- error/
             |   +- 5xx.ftl
             +- <other templates>

For more complex mappings, you can also add beans that implement the ErrorViewResolver interface, as shown in the following example:

public class MyErrorViewResolver implements ErrorViewResolver {
	@Override
	public ModelAndView resolveErrorView(HttpServletRequest request,
			HttpStatus status, Map<String, Object> model) {
		// Use the request or status to optionally return a ModelAndView
		return ...
}

You can also use regular Spring MVC features such as @ExceptionHandler methods and @ControllerAdvice . The ErrorController then picks up any unhandled exceptions.

Mapping Error Pages outside of Spring MVC

For applications that do not use Spring MVC, you can use the ErrorPageRegistrar interface to directly register ErrorPages . This abstraction works directly with the underlying embedded servlet container and works even if you do not have a Spring MVC DispatcherServlet .

@Bean
public ErrorPageRegistrar errorPageRegistrar(){
	return new MyErrorPageRegistrar();
// ...
private static class MyErrorPageRegistrar implements ErrorPageRegistrar {
	@Override
	public void registerErrorPages(ErrorPageRegistry registry) {
		registry.addErrorPages(new ErrorPage(HttpStatus.BAD_REQUEST, "/400"));
}

	Note
	If you register an `ErrorPage` with a path that ends up being handled by a `Filter` (as is common with some non-Spring web frameworks, like Jersey and Wicket), then the `Filter` has to be explicitly registered as an `ERROR` dispatcher, as shown in the following example:

@Bean
public FilterRegistrationBean myFilter() {
	FilterRegistrationBean registration = new FilterRegistrationBean();
	registration.setFilter(new MyFilter());
	registration.setDispatcherTypes(EnumSet.allOf(DispatcherType.class));
	return registration;
}

Note that the default FilterRegistrationBean does not include the ERROR dispatcher type.

Error Handling on WebSphere Application Server

When deployed to a servlet container, Spring Boot uses its error page filter to forward a request with an error status to the appropriate error page. The request can only be forwarded to the correct error page if the response has not already been committed. By default, WebSphere Application Server 8.0 and later commits the response upon successful completion of a servlet’s service method. You should disable this behavior by setting com.ibm.ws.webcontainer.invokeFlushAfterService to false .

27.1.11 Spring HATEOAS

If you develop a RESTful API that makes use of hypermedia, Spring Boot provides auto-configuration for Spring HATEOAS that works well with most applications. The auto-configuration replaces the need to use @EnableHypermediaSupport and registers a number of beans to ease building hypermedia-based applications, including a LinkDiscoverers (for client side support) and an ObjectMapper configured to correctly marshal responses into the desired representation. The ObjectMapper is customized by setting the various spring.jackson.* properties or, if one exists, by a Jackson2ObjectMapperBuilder bean.

You can take control of Spring HATEOAS’s configuration by using @EnableHypermediaSupport . Note that this disables the ObjectMapper customization described earlier.

27.1.12 CORS Support

Cross-origin resource sharing (CORS) is a W3C specification implemented by most browsers that allows you to specify in a flexible way what kind of cross-domain requests are authorized, instead of using some less secure and less powerful approaches such as IFRAME or JSONP.

As of version 4.2, Spring MVC supports CORS . Using controller method CORS configuration with @CrossOrigin annotations in your Spring Boot application does not require any specific configuration. Global CORS configuration can be defined by registering a WebMvcConfigurer bean with a customized addCorsMappings(CorsRegistry) method, as shown in the following example:

@Configuration
public class MyConfiguration {
	@Bean
	public WebMvcConfigurer corsConfigurer() {
		return new WebMvcConfigurer() {
			@Override
			public void addCorsMappings(CorsRegistry registry) {
				registry.addMapping("/api/**");
}

27.2 The ‘Spring WebFlux Framework’

Spring WebFlux is the new reactive web framework introduced in Spring Framework 5.0. Unlike Spring MVC, it does not require the Servlet API, is fully asynchronous and non-blocking, and implements the Reactive Streams specification through the Reactor project .

Spring WebFlux comes in two flavors: functional and annotation-based. The annotation-based one is quite close to the Spring MVC model we know, as shown in the following example:

@RestController
@RequestMapping("/users")
public class MyRestController {
	@GetMapping("/{user}")
	public Mono<User> getUser(@PathVariable Long user) {
		// ...
	@GetMapping("/{user}/customers")
	Flux<Customer> getUserCustomers(@PathVariable Long user) {
		// ...
	@DeleteMapping("/{user}")
	public Mono<User> deleteUser(@PathVariable Long user) {
		// ...
}

‘WebFlux.fn’, the functional variant, separates the routing configuration from the actual handling of the requests, as shown in the following example:

@Configuration
public class RoutingConfiguration {
	@Bean
	public RouterFunction<ServerResponse> monoRouterFunction(UserHandler userHandler) {
		return route(GET("/{user}").and(accept(APPLICATION_JSON)), userHandler::getUser)
				.andRoute(GET("/{user}/customers").and(accept(APPLICATION_JSON)), userHandler::getUserCustomers)
				.andRoute(DELETE("/{user}").and(accept(APPLICATION_JSON)), userHandler::deleteUser);
@Component
public class UserHandler {
	public Mono<ServerResponse> getUser(ServerRequest request) {
		// ...
	public Mono<ServerResponse> getUserCustomers(ServerRequest request) {
		// ...
	public Mono<ServerResponse> deleteUser(ServerRequest request) {
		// ...
}

WebFlux is part of the Spring Framework. and detailed information is available in its reference documentation .

To get started, add the spring-boot-starter-webflux module to your application.

Note

Adding both spring-boot-starter-web and spring-boot-starter-webflux modules in your application results in Spring Boot auto-configuring Spring MVC, not WebFlux. This behavior has been chosen because many Spring developers add spring-boot-starter-webflux to their Spring MVC application to use the reactive WebCLient . You can still enforce your choice by setting the chosen application type to SpringApplication.setWebApplicationType(WebApplicationType.REACTIVE) .

27.2.1 Spring WebFlux Auto-configuration

Spring Boot provides auto-configuration for Spring WebFlux that works well with most applications.

The auto-configuration adds the following features on top of Spring’s defaults:

Configuring codecs for HttpMessageReader and HttpMessageWriter instances (described later in this document).
Support for serving static resources, including support for WebJars (described later in this document).

If you want to keep Spring Boot WebFlux features and you want to add additional WebFlux configuration , you can add your own @Configuration class of type WebFluxConfigurer but without @EnableWebFlux .

If you want to take complete control of Spring WebFlux, you can add your own @Configuration annotated with @EnableWebFlux .

27.2.2 HTTP Codecs with HttpMessageReaders and HttpMessageWriters

Spring WebFlux uses the HttpMessageReader and HttpMessageWriter interfaces to convert HTTP requests and responses. They are configured with CodecConfigurer to have sensible defaults by looking at the libraries available in your classpath.

Spring Boot applies further customization by using CodecCustomizer instances. For example, spring.jackson.* configuration keys are applied to the Jackson codec.

If you need to add or customize codecs, you can create a custom CodecCustomizer component, as shown in the following example:

import org.springframework.boot.web.codec.CodecCustomizer;
@Configuration
public class MyConfiguration {
	@Bean
	public CodecCustomizer myCodecCustomizer() {
		return codecConfigurer -> {
			// ...
}

You can also leverage Boot’s custom JSON serializers and deserializers .

27.2.3 Static Content

By default, Spring Boot serves static content from a directory called /static (or /public or /resources or /META-INF/resources ) in the classpath. It uses the ResourceWebHandler from Spring WebFlux so that you can modify that behavior by adding your own WebFluxConfigurer and overriding the addResourceHandlers method.

By default, resources are mapped on /** , but you can tune that by setting the spring.webflux.static-path-pattern property. For instance, relocating all resources to /resources/** can be achieved as follows:

spring.webflux.static-path-pattern=/resources/**

You can also customize the static resource locations by using spring.resources.static-locations . Doing so replaces the default values with a list of directory locations. If you do so, the default welcome page detection switches to your custom locations. So, if there is an index.html in any of your locations on startup, it is the home page of the application.

In addition to the ‘standard’ static resource locations listed earlier, a special case is made for Webjars content . Any resources with a path in /webjars/** are served from jar files if they are packaged in the Webjars format.

	Tip
	Spring WebFlux applications do not strictly depend on the Servlet API, so they cannot be deployed as war files and do not use the `src/main/webapp` directory.

27.2.4 Template Engines

As well as REST web services, you can also use Spring WebFlux to serve dynamic HTML content. Spring WebFlux supports a variety of templating technologies, including Thymeleaf, FreeMarker, and Mustache.

Spring Boot includes auto-configuration support for the following templating engines:

When you use one of these templating engines with the default configuration, your templates are picked up automatically from src/main/resources/templates .

27.2.5 Error Handling

Spring Boot provides a WebExceptionHandler that handles all errors in a sensible way. Its position in the processing order is immediately before the handlers provided by WebFlux, which are considered last. For machine clients it will produce a JSON response with details of the error, the HTTP status and the exception message. For browser clients there is a ‘whitelabel’ error handler that renders the same data in HTML format. You can also provide your own HTML templates to display errors (see the next section ).

The first step to customizing this feature is often about using the existing mechanism but replacing or augmenting the error contents. For that, you can simply add a bean of type ErrorAttributes .

To change the error handling behavior, you can implement ErrorWebExceptionHandler and register a bean definition of that type. Because a WebExceptionHandler is quite low-level, Spring Boot also provides a convenient AbstractErrorWebExceptionHandler to let you handle errors in a WebFlux functional way, as shown in the following example:

public class CustomErrorWebExceptionHandler extends AbstractErrorWebExceptionHandler {
	// Define constructor here
	@Override
	protected RouterFunction<ServerResponse> getRoutingFunction(ErrorAttributes errorAttributes) {
		return RouterFunctions
				.route(aPredicate, aHandler)
				.andRoute(anotherPredicate, anotherHandler);
}

For a more complete picture, you can also subclass DefaultErrorWebExceptionHandler directly and override specific methods.

Custom Error Pages

If you want to display a custom HTML error page for a given status code, you can add a file to an /error folder. Error pages can either be static HTML (that is, added under any of the static resource folders) or built with templates. The name of the file should be the exact status code or a series mask.

For example, to map 404 to a static HTML file, your folder structure would be as follows:

src/
 +- main/
     +- java/
     |   + <source code>
     +- resources/
         +- public/
             +- error/
             |   +- 404.html
             +- <other public assets>

To map all 5xx errors by using a Mustache template, your folder structure would be as follows:

src/
 +- main/
     +- java/
     |   + <source code>
     +- resources/
         +- templates/
             +- error/
             |   +- 5xx.mustache
             +- <other templates>

27.3 JAX-RS and Jersey

If you prefer the JAX-RS programming model for REST endpoints, you can use one of the available implementations instead of Spring MVC. Jersey 1.x and Apache CXF work quite well out of the box if you register their Servlet or Filter as a @Bean in your application context. Jersey 2.x has some native Spring support, so we also provide auto-configuration support for it in Spring Boot, together with a starter.

To get started with Jersey 2.x, include the spring-boot-starter-jersey as a dependency and then you need one @Bean of type ResourceConfig in which you register all the endpoints, as shown in the following example:

@Component
public class JerseyConfig extends ResourceConfig {
	public JerseyConfig() {
		register(Endpoint.class);
}

	Warning
	Jersey’s support for scanning executable archives is rather limited. For example, it cannot scan for endpoints in a package found in `WEB-INF/classes` when running an executable war file. To avoid this limitation, the `packages` method should not be used, and endpoints should be registered individually by using the `register` method, as shown in the preceding example.

You can also register an arbitrary number of beans implementing ResourceConfigCustomizer for more advanced customizations.

All the registered endpoints should be @Components with HTTP resource annotations ( @GET etc.), as shown in the following example:

@Component
@Path("/hello")
public class Endpoint {
	public String message() {
		return "Hello";
}

Since the Endpoint is a Spring @Component , its lifecycle is managed by Spring and you can use the @Autowired annotation to inject dependencies and use the @Value annotation to inject external configuration. By default, the Jersey servlet is registered and mapped to /* . You can change the mapping by adding @ApplicationPath to your ResourceConfig .

By default, Jersey is set up as a Servlet in a @Bean of type ServletRegistrationBean named jerseyServletRegistration . By default, the servlet is initialized lazily, but you can customize that behavior by setting spring.jersey.servlet.load-on-startup . You can disable or override that bean by creating one of your own with the same name. You can also use a filter instead of a servlet by setting spring.jersey.type=filter (in which case, the @Bean to replace or override is jerseyFilterRegistration ). The filter has an @Order , which you can set with spring.jersey.filter.order . Both the servlet and the filter registrations can be given init parameters by using spring.jersey.init.* to specify a map of properties.

There is a Jersey sample so that you can see how to set things up. There is also a Jersey 1.x sample . Note that, in the Jersey 1.x sample, the spring-boot maven plugin has been configured to unpack some Jersey jars so that they can be scanned by the JAX-RS implementation (because the sample asks for them to be scanned in its Filter registration). If any of your JAX-RS resources are packaged as nested jars, you may need to do the same.

27.4 Embedded Servlet Container Support

Spring Boot includes support for embedded Tomcat, Jetty, and Undertow servers. Most developers use the appropriate ‘Starter’ to obtain a fully configured instance. By default, the embedded server listens for HTTP requests on port 8080 .

Warning

If you choose to use Tomcat on CentOS, be aware that, by default, a temporary directory is used to store compiled JSPs, file uploads, and so on. This directory may be deleted by tmpwatch while your application is running, leading to failures. To avoid this behavior, you may want to customize your tmpwatch configuration, so that tomcat.* directories are not deleted or configure server.tomcat.basedir , so that embedded Tomcat uses a different location.

27.4.1 Servlets, Filters, and listeners

When using an embedded servlet container, you can register servlets, filters, and all the listeners (such as HttpSessionListener ) from the Servlet spec, either by using Spring beans or by scanning for Servlet components.

Registering Servlets, Filters, and Listeners as Spring Beans

Any Servlet , Filter , or servlet *Listener instance that is a Spring bean is registered with the embedded container. This can be particularly convenient if you want to refer to a value from your application.properties during configuration.

By default, if the context contains only a single Servlet, it is mapped to / . In the case of multiple servlet beans, the bean name is used as a path prefix. Filters map to /* .

If convention-based mapping is not flexible enough, you can use the ServletRegistrationBean , FilterRegistrationBean , and ServletListenerRegistrationBean classes for complete control.

27.4.2 Servlet Context Initialization

Embedded servlet containers do not directly execute the Servlet 3.0+ javax.servlet.ServletContainerInitializer interface or Spring’s org.springframework.web.WebApplicationInitializer interface. This is an intentional design decision intended to reduce the risk that third party libraries designed to run inside a war may break Spring Boot applications.

If you need to perform servlet context initialization in a Spring Boot application, you should register a bean that implements the org.springframework.boot.web.servlet.ServletContextInitializer interface. The single onStartup method provides access to the ServletContext and, if necessary, can easily be used as an adapter to an existing WebApplicationInitializer .

Scanning for Servlets, Filters, and listeners

When using an embedded container, automatic registration of @WebServlet , @WebFilter , and @WebListener annotated classes can be enabled by using @ServletComponentScan .

	Tip
	`@ServletComponentScan` has no effect in a standalone container, where the container’s built-in discovery mechanisms are used instead.

27.4.3 The ServletWebServerApplicationContext

Under the hood, Spring Boot uses a new type of ApplicationContext for embedded servlet container support. The ServletWebServerApplicationContext is a special type of WebApplicationContext that bootstraps itself by searching for a single ServletWebServerFactory bean. Usually a TomcatServletWebServerFactory , JettyServletWebServerFactory , or UndertowServletWebServerFactory has been auto-configured.

	Note
	You usually do not need to be aware of these implementation classes. Most applications are auto-configured, and the appropriate `ApplicationContext` and `ServletWebServerFactory` are created on your behalf.

27.4.4 Customizing Embedded Servlet Containers

Common servlet container settings can be configured by using Spring Environment properties. Usually, you would define the properties in your application.properties file.

Common server settings include:

Network settings: Listen port for incoming HTTP requests ( server.port ), interface address to bind to server.address , and so on.
Session settings: Whether the session is persistent ( server.session.persistence ), session timeout ( server.session.timeout ), location of session data ( server.session.store-dir ), and session-cookie configuration ( server.session.cookie.* ).
Error management: Location of the error page ( server.error.path ), and so on.
SSL
HTTP compression

Spring Boot tries as much as possible to expose common settings, but this is not always possible. For those cases, dedicated namespaces offer server-specific customizations (see server.tomcat and server.undertow ). For instance, access logs can be configured with specific features of the embedded servlet container.

	Tip
	See the `ServerProperties` class for a complete list.

Programmatic Customization

If you need to programmatically configure your embedded servlet container, you can register a Spring bean that implements the WebServerFactoryCustomizer interface. WebServerFactoryCustomizer provides access to the ConfigurableServletWebServerFactory , which includes numerous customization setter methods. Dedicated variants exist for Tomcat, Jetty, and Undertow. The following example shows programmatically setting the port:

import org.springframework.boot.web.server.WebServerFactoryCustomizer;
import org.springframework.boot.web.servlet.server.ConfigurableServletWebServerFactory;
import org.springframework.stereotype.Component;
@Component
public class CustomizationBean implements WebServerFactoryCustomizer<ConfigurableServletWebServerFactory> {
	@Override
	public void customize(ConfigurableServletWebServerFactory server) {
		server.setPort(9000);
}

Customizing ConfigurableServletWebServerFactory Directly

If the preceding customization techniques are too limited, you can register the TomcatServletWebServerFactory , JettyServletWebServerFactory , or UndertowServletWebServerFactory bean yourself.

@Bean
public ConfigurableServletWebServerFactory webServerFactory() {
	TomcatServletWebServerFactory factory = new TomcatServletWebServerFactory();
	factory.setPort(9000);
	factory.setSessionTimeout(10, TimeUnit.MINUTES);
	factory.addErrorPages(new ErrorPage(HttpStatus.NOT_FOUND, "/notfound.html"));
	return factory;
}

Setters are provided for many configuration options. Several protected method “hooks” are also provided should you need to do something more exotic. See the source code documentation for details.

27.4.5 JSP Limitations

When running a Spring Boot application that uses an embedded servlet container (and is packaged as an executable archive), there are some limitations in the JSP support.

With Tomcat, it should work if you use war packaging. That is, an executable war works and is also deployable to a standard container (not limited to, but including Tomcat). An executable jar does not work because of a hard-coded file pattern in Tomcat.
With Jetty, it should work if you use war packaging. That is, an executable war works, and is also deployable to any standard container.
Undertow does not support JSPs.
Creating a custom error.jsp page does not override the default view for error handling . Custom error pages should be used instead.

There is a JSP sample so that you can see how to set things up.

28. Security

If Spring Security is on the classpath, then web applications are secure by default. Spring Boot relies on Spring Security’s content-negotiation strategy to determine whether to use httpBasic or formLogin . To add method-level security to a web application, you can also add @EnableGlobalMethodSecurity with your desired settings. Additional information can be found in the Spring Security Reference .

The default AuthenticationManager has a single user (the user name is ‘user’, and the password is random and is printed at INFO level when the application starts), as shown in the following example:

Using default security password: 78fa095d-3f4c-48b1-ad50-e24c31d5cf35

	Note
	If you fine-tune your logging configuration, ensure that the `org.springframework.boot.autoconfigure.security` category is set to log `INFO` -level messages. Otherwise, the default password is not printed.

The default security configuration is implemented in SecurityAutoConfiguration and in the classes imported from there ( SpringBootWebSecurityConfiguration for web security and AuthenticationManagerConfiguration for authentication configuration, which is also relevant in non-web applications). To switch off the default web application security configuration completely, you can add a bean of type WebSecurityConfigurerAdapter (this does not disable the authentication manager configuration or Actuator’s security).

To also switch off the authentication manager configuration, you can add a bean of type UserDetailsService , AuthenticationProvider or AuthenticationManager . There are several secure applications in the Spring Boot samples to get you started with common use cases.

The basic features you get by default in a web application are:

A UserDetailsService bean with in-memory store and a single user with a generated password.
Form-based login or HTTP Basic security (depending on Content-Type) for the entire application (including actuator endpoints if actuator is on the classpath).

Access rules can be overriden by adding a custom WebSecurityConfigurerAdapter . Spring Boot provides convenience methods that can be used to override access rules for actuator endpoints and static resources. EndpointRequest can be used to create a RequestMatcher that is based on the management.endpoints.web.base-path property. StaticResourceRequest can be used to create a RequestMatcher for static resources in commonly used locations.

28.1 OAuth2

OAuth2 is a widely used authorization framework that is supported by Spring.

28.1.1 Client

If you have spring-security-oauth2-client on your classpath, you can take advantage of some auto-configuration to make it easy to set up an OAuth2 Client. This configuration makes use of the properties under OAuth2ClientProperties .

You can register multiple OAuth2 clients and providers under the spring.security.oauth2.client prefix, as shown in the following example:

spring.security.oauth2.client.registration.my-client-1.client-id=abcd
spring.security.oauth2.client.registration.my-client-1.client-secret=password
spring.security.oauth2.client.registration.my-client-1.client-name=Client for user scope
spring.security.oauth2.client.registration.my-client-1.provider=my-oauth-provider
spring.security.oauth2.client.registration.my-client-1.scope=user
spring.security.oauth2.client.registration.my-client-1.redirect-uri-template=http://my-redirect-uri.com
spring.security.oauth2.client.registration.my-client-1.client-authentication-method=basic
spring.security.oauth2.client.registration.my-client-1.authorization-grant-type=authorization_code
spring.security.oauth2.client.registration.my-client-2.client-id=abcd
spring.security.oauth2.client.registration.my-client-2.client-secret=password
spring.security.oauth2.client.registration.my-client-2.client-name=Client for email scope
spring.security.oauth2.client.registration.my-client-2.provider=my-oauth-provider
spring.security.oauth2.client.registration.my-client-2.scope=email
spring.security.oauth2.client.registration.my-client-2.redirect-uri-template=http://my-redirect-uri.com
spring.security.oauth2.client.registration.my-client-2.client-authentication-method=basic
spring.security.oauth2.client.registration.my-client-2.authorization-grant-type=authorization_code
spring.security.oauth2.client.provider.my-oauth-provider.authorization-uri=http://my-auth-server/oauth/authorize
spring.security.oauth2.client.provider.my-oauth-provider.token-uri=http://my-auth-server/oauth/token
spring.security.oauth2.client.provider.my-oauth-provider.user-info-uri=http://my-auth-server/userinfo
spring.security.oauth2.client.provider.my-oauth-provider.jwk-set-uri=http://my-auth-server/token_keys
spring.security.oauth2.client.provider.my-oauth-provider.user-name-attribute=name

By default, Spring Security’s OAuth2LoginAuthenticationFilter will only process URLs matching /login/oauth2/code/* . If you want to customize the redirect-uri-template to use a different pattern, you will need to provide configuration to process that custom pattern. For example, you can add your own WebSecurityConfigurerAdapter that looks like this:

public class OAuth2LoginSecurityConfig extends WebSecurityConfigurerAdapter {
	@Override
	protected void configure(HttpSecurity http) throws Exception {
			.authorizeRequests()
				.anyRequest().authenticated()
				.and()
			.oauth2Login()
				.redirectionEndpoint()
					.baseUri("/custom-callback");
}

For common OAuth2 and OpenID providers such as Google, Github, Facebook, and Okta, we provide a set of provider defaults ( google , github , facebook , and okta respectively).

If you do not need to customize these providers, you can set the provider attribute to the one for which you need to infer defaults. Also if the ID of your client matches the default supported provider, Spring Boot infers that as well.

In other words, the two configurations in the following example use the Google provider:

spring.security.oauth2.client.registration.my-client.client-id=abcd
spring.security.oauth2.client.registration.my-client.client-secret=password
spring.security.oauth2.client.registration.my-client.provider=google
spring.security.oauth2.client.registration.google.client-id=abcd
spring.security.oauth2.client.registration.google.client-secret=password

28.2 Actuator Security

If the Actuator is also in use, you can see that:

The management endpoints are secure even if the application endpoints are insecure.
Security events are transformed into AuditEvent instances and published to the AuditEventRepository .
The default user has the ACTUATOR role as well as the USER role.

The Actuator security features can be modified by using external properties ( management.security.* ). To override the application access rules but not the actuator access rules, add a @Bean of type WebSecurityConfigurerAdapter and use @Order(SecurityProperties.ACCESS_OVERRIDE_ORDER) . Use @Order(ManagementServerProperties.ACCESS_OVERRIDE_ORDER) if you do want to override the application access rules and the actuator access rules.

29. Working with SQL Databases

The Spring Framework provides extensive support for working with SQL databases, from direct JDBC access using JdbcTemplate to complete ‘object relational mapping’ technologies such as Hibernate. Spring Data provides an additional level of functionality: creating Repository implementations directly from interfaces and using conventions to generate queries from your method names.

29.1 Configure a DataSource

Java’s javax.sql.DataSource interface provides a standard method of working with database connections. Traditionally, a DataSource uses a URL along with some credentials to establish a database connection.

	Tip
	See the ‘How-to’ section for more advanced examples, typically to take full control over the configuration of the DataSource.

29.1.1 Embedded Database Support

It is often convenient to develop applications using an in-memory embedded database. Obviously, in-memory databases do not provide persistent storage. You need to populate your database when your application starts and be prepared to throw away data when your application ends.

	Tip
	The ‘How-to’ section includes a section on how to initialize a database .

Spring Boot can auto-configure embedded H2 , HSQL , and Derby databases. You need not provide any connection URLs. You need only include a build dependency to the embedded database that you want to use.

	Note
	If you are using this feature in your tests, you may notice that the same database is reused by your whole test suite regardless of the number of application contexts that you use. If you want to make sure that each context has a separate embedded database, you should set `spring.datasource.generate-unique-name` to `true` .

For example, typical POM dependencies would be as follows:

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
	<groupId>org.hsqldb</groupId>
	<artifactId>hsqldb</artifactId>
	<scope>runtime</scope>
</dependency>

	Note
	You need a dependency on `spring-jdbc` for an embedded database to be auto-configured. In this example, it is pulled in transitively via `spring-boot-starter-data-jpa` .

Tip

If, for whatever reason, you do configure the connection URL for an embedded database, take care to ensure that the database’s automatic shutdown is disabled. If you use H2, you should use DB_CLOSE_ON_EXIT=FALSE to do so. If you use HSQLDB, you should ensure that shutdown=true is not used. Disabling the database’s automatic shutdown lets Spring Boot control when the database is closed, thereby ensuring that it happens once access to the database is no longer needed.

29.1.2 Connection to a Production Database

Production database connections can also be auto-configured by using a pooling DataSource . Spring Boot uses the following algorithm for choosing a specific implementation:

We prefer HikariCP for its performance and concurrency. If HikariCP is available, we always choose it.
Otherwise, if the Tomcat pooling DataSource is available, we use it.
If neither HikariCP nor the Tomcat pooling datasource are available and if Commons DBCP2 is available, we use it.

If you use the spring-boot-starter-jdbc or spring-boot-starter-data-jpa ‘starters’, you automatically get a dependency to HikariCP .

	Note
	You can bypass that algorithm completely and specify the connection pool to use by setting the `spring.datasource.type` property. This is especially important if you are running your application in a Tomcat container, as `tomcat-jdbc` is provided by default.

	Tip
	Additional connection pools can always be configured manually. If you define your own `DataSource` bean, auto-configuration does not occur.

DataSource configuration is controlled by external configuration properties in spring.datasource.* . For example, you might declare the following section in application.properties :

spring.datasource.url=jdbc:mysql://localhost/test
spring.datasource.username=dbuser
spring.datasource.password=dbpass
spring.datasource.driver-class-name=com.mysql.jdbc.Driver

	Note
	You should at least specify the URL by setting the `spring.datasource.url` property. Otherwise, Spring Boot tries to auto-configure an embedded database.

	Tip
	You often do not need to specify the `driver-class-name` , since Spring Boot can deduce it for most databases from the `url` .

	Note
	For a pooling `DataSource` to be created, we need to be able to verify that a valid `Driver` class is available, so we check for that before doing anything. In other words, if you set `spring.datasource.driver-class-name=com.mysql.jdbc.Driver` then that class has to be loadable.

See DataSourceProperties for more of the supported options. These are the standard options that work regardless of the actual implementation. It is also possible to fine-tune implementation-specific settings using their respective prefix ( spring.datasource.hikari.* , spring.datasource.tomcat.* , and spring.datasource.dbcp2.* ). Refer to the documentation of the connection pool implementation you are using for more details.

For instance, if you use the Tomcat connection pool , you could customize many additional settings:

# Number of ms to wait before throwing an exception if no connection is available.
spring.datasource.tomcat.max-wait=10000
# Maximum number of active connections that can be allocated from this pool at the same time.
spring.datasource.tomcat.max-active=50
# Validate the connection before borrowing it from the pool.
spring.datasource.tomcat.test-on-borrow=true

29.1.3 Connection to a JNDI DataSource

If you deploy your Spring Boot application to an Application Server, you might want to configure and manage your DataSource using your Application Server’s built-in features and access it by using JNDI.

The spring.datasource.jndi-name property can be used as an alternative to the spring.datasource.url , spring.datasource.username , and spring.datasource.password properties to access the DataSource from a specific JNDI location. For example, the following section in application.properties shows how you can access a JBoss AS defined DataSource :

spring.datasource.jndi-name=java:jboss/datasources/customers

29.2 Using JdbcTemplate

Spring’s JdbcTemplate and NamedParameterJdbcTemplate classes are auto-configured, and you can @Autowire them directly into your own beans, as shown in the following example:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Component;
@Component
public class MyBean {
	private final JdbcTemplate jdbcTemplate;
	@Autowired
	public MyBean(JdbcTemplate jdbcTemplate) {
		this.jdbcTemplate = jdbcTemplate;
	// ...
}

You can customize some properties of the template by using the spring.jdbc.template.* properties as shown in the following example:

spring.jdbc.template.max-rows=500

	Note
	The `NamedParameterJdbcTemplate` reuses the same `JdbcTemplate` instance behind the scenes. If more than one `JdbcTemplate` is defined and no primary candidate exists, the `NamedParameterJdbcTemplate` is not auto-configured.

29.3 JPA and ‘Spring Data’

The Java Persistence API is a standard technology that lets you ‘map’ objects to relational databases. The spring-boot-starter-data-jpa POM provides a quick way to get started. It provides the following key dependencies:

Hibernate — One of the most popular JPA implementations.
Spring Data JPA — Makes it easy to implement JPA-based repositories.
Spring ORMs — Core ORM support from the Spring Framework.

	Tip
	We do not go into too many details of JPA or Spring Data here. You can follow the ‘Accessing Data with JPA’ guide from spring.io and read the Spring Data JPA and Hibernate reference documentation.

29.3.1 Entity Classes

Traditionally, JPA ‘Entity’ classes are specified in a persistence.xml file. With Spring Boot, this file is not necessary and ‘Entity Scanning’ is used instead. By default, all packages below your main configuration class (the one annotated with @EnableAutoConfiguration or @SpringBootApplication ) are searched.

Any classes annotated with @Entity , @Embeddable or @MappedSuperclass are considered. A typical entity class resembles the following example:

package com.example.myapp.domain;
import java.io.Serializable;
import javax.persistence.*;
@Entity
public class City implements Serializable {
	@GeneratedValue
	private Long id;
	@Column(nullable = false)
	private String name;
	@Column(nullable = false)
	private String state;
	// ... additional members, often include @OneToMany mappings
	protected City() {
		// no-args constructor required by JPA spec
		// this one is protected since it shouldn't be used directly
	public City(String name, String state) {
		this.name = name;
		this.country = country;
	public String getName() {
		return this.name;
	public String getState() {
		return this.state;
	// ... etc
}

	Tip
	You can customize entity scanning locations by using the `@EntityScan` annotation. See the “ Section 78.4, “Separate @Entity Definitions from Spring Configuration” ” how-to.

29.3.2 Spring Data JPA Repositories

Spring Data JPA repositories are interfaces that you can define to access data. JPA queries are created automatically from your method names. For example, a CityRepository interface might declare a findAllByState(String state) method to find all the cities in a given state.

For more complex queries, you can annotate your method with Spring Data’s Query annotation.

Spring Data repositories usually extend from the Repository or CrudRepository interfaces. If you use auto-configuration, repositories are searched from the package containing your main configuration class (the one annotated with @EnableAutoConfiguration or @SpringBootApplication ) down.

The following example shows a typical Spring Data repository interface definition:

package com.example.myapp.domain;
import org.springframework.data.domain.*;
import org.springframework.data.repository.*;
public interface CityRepository extends Repository<City, Long> {
	Page<City> findAll(Pageable pageable);
	City findByNameAndCountryAllIgnoringCase(String name, String country);
}

	Tip
	We have barely scratched the surface of Spring Data JPA. For complete details, see the Spring Data JPA reference documentation .

29.3.3 Creating and Dropping JPA Databases

By default, JPA databases are automatically created only if you use an embedded database (H2, HSQL, or Derby). You can explicitly configure JPA settings by using spring.jpa.* properties. For example, to create and drop tables you can add the following line to your application.properties :

spring.jpa.hibernate.ddl-auto=create-drop

	Note
	Hibernate’s own internal property name for this (if you happen to remember it better) is `hibernate.hbm2ddl.auto` . You can set it, along with other Hibernate native properties, by using `spring.jpa.properties.*` (the prefix is stripped before adding them to the entity manager). The following line shows an example of setting JPA properties for Hibernate:

spring.jpa.properties.hibernate.globally_quoted_identifiers=true

The line in the preceding example passes a value of true for the hibernate.globally_quoted_identifiers property to the Hibernate entity manager.

By default, the DDL execution (or validation) is deferred until the ApplicationContext has started. There is also a spring.jpa.generate-ddl flag, but it is not used if Hibernate auto-configuration is active, because the ddl-auto settings are more fine-grained.

29.3.4 Open EntityManager in View

If you are running a web application, Spring Boot by default registers OpenEntityManagerInViewInterceptor to apply the "Open EntityManager in View" pattern, to allow for lazy loading in web views. If you do not want this behavior, you should set spring.jpa.open-in-view to false in your application.properties .

29.4 Using H2’s Web Console

The H2 database provides a browser-based console that Spring Boot can auto-configure for you. The console is auto-configured when the following conditions are met:

You are developing a web application.
com.h2database:h2 is on the classpath.
You are using Spring Boot’s developer tools .

	Tip
	If you are not using Spring Boot’s developer tools but would still like to make use of H2’s console, you can configure the `spring.h2.console.enabled` property with a value of `true` . The H2 console is only intended for use during development, so you should take care to ensure that `spring.h2.console.enabled` is not set to `true` in production.

29.4.1 Changing the H2 Console’s Path

By default, the console is available at /h2-console . You can customize the console’s path by using the spring.h2.console.path property.

29.5 Using jOOQ

Java Object Oriented Querying ( jOOQ ) is a popular product from Data Geekery which generates Java code from your database and lets you build type-safe SQL queries through its fluent API. Both the commercial and open source editions can be used with Spring Boot.

29.5.1 Code Generation

In order to use jOOQ type-safe queries, you need to generate Java classes from your database schema. You can follow the instructions in the jOOQ user manual . If you use the jooq-codegen-maven plugin and you also use the spring-boot-starter-parent “parent POM”, you can safely omit the plugin’s <version> tag. You can also use Spring Boot-defined version variables (such as h2.version ) to declare the plugin’s database dependency. The following listing shows an example:

<plugin>
	<groupId>org.jooq</groupId>
	<artifactId>jooq-codegen-maven</artifactId>
	<executions>
	</executions>
	<dependencies>
		<dependency>
			<groupId>com.h2database</groupId>
			<artifactId>h2</artifactId>
			<version>${h2.version}</version>
		</dependency>
	</dependencies>
	<configuration>
			<driver>org.h2.Driver</driver>
			<url>jdbc:h2:~/yourdatabase</url>
		</jdbc>
		<generator>
		</generator>
	</configuration>
</plugin>

29.5.2 Using DSLContext

The fluent API offered by jOOQ is initiated through the org.jooq.DSLContext interface. Spring Boot auto-configures a DSLContext as a Spring Bean and connects it to your application DataSource . To use the DSLContext , you can @Autowire it, as shown in the following example:

@Component
public class JooqExample implements CommandLineRunner {
	private final DSLContext create;
	@Autowired
	public JooqExample(DSLContext dslContext) {
		this.create = dslContext;
}

	Tip
	The jOOQ manual tends to use a variable named `create` to hold the `DSLContext` .

You can then use the DSLContext to construct your queries, as shown in the following example:

public List<GregorianCalendar> authorsBornAfter1980() {
	return this.create.selectFrom(AUTHOR)
		.where(AUTHOR.DATE_OF_BIRTH.greaterThan(new GregorianCalendar(1980, 0, 1)))
		.fetch(AUTHOR.DATE_OF_BIRTH);
}

29.5.3 jOOQ SQL Dialect

Unless the spring.jooq.sql-dialect property has been configured, Spring Boot determines the SQL dialect to use for your datasource. If Spring Boot could not detect the dialect, it uses DEFAULT .

	Note
	Spring Boot can only auto-configure dialects supported by the open source version of jOOQ.

29.5.4 Customizing jOOQ

More advanced customizations can be achieved by defining your own @Bean definitions, which will be used when the jOOQ Configuration is created. You can define beans for the following jOOQ Types:

ConnectionProvider
TransactionProvider
RecordMapperProvider
RecordListenerProvider
ExecuteListenerProvider
VisitListenerProvider

You can also create your own org.jooq.Configuration @Bean if you want to take complete control of the jOOQ configuration.

30. Working with NoSQL Technologies

Spring Data provides additional projects that help you access a variety of NoSQL technologies, including: MongoDB , Neo4J , Elasticsearch , Solr , Redis , Gemfire , Cassandra , Couchbase and LDAP . Spring Boot provides auto-configuration for Redis, MongoDB, Neo4j, Elasticsearch, Solr Cassandra, Couchbase, and LDAP. You can make use of the other projects, but you must configure them yourself. Refer to the appropriate reference documentation at projects.spring.io/spring-data .

30.1 Redis

Redis is a cache, message broker, and richly-featured key-value store. Spring Boot offers basic auto-configuration for the Lettuce and Jedis client libraries and the abstractions on top of them provided by Spring Data Redis .

There is a spring-boot-starter-data-redis ‘Starter’ for collecting the dependencies in a convenient way. By default, it uses Lettuce . That starter handles both traditional and reactive applications.

	Tip
	we also provide a `spring-boot-starter-data-redis-reactive` ‘Starter’ for consistency with the other stores with reactive support.

30.1.1 Connecting to Redis

You can inject an auto-configured RedisConnectionFactory , StringRedisTemplate , or vanilla RedisTemplate instance as you would any other Spring Bean. By default, the instance tries to connect to a Redis server at localhost:6379 . The following listing shows an example of such a bean:

@Component
public class MyBean {
	private StringRedisTemplate template;
	@Autowired
	public MyBean(StringRedisTemplate template) {
		this.template = template;
	// ...
}

	Tip
	You can also register an arbitrary number of beans that implement `LettuceClientConfigurationBuilderCustomizer` for more advanced customizations. If you use Jedis, `JedisClientConfigurationBuilderCustomizer` is also available.

If you add your own @Bean of any of the auto-configured types, it replaces the default (except in the case of RedisTemplate , when the exclusion is based on the bean name ‘redisTemplate’, not its type). By default, if commons-pool2 is on the classpath, you get a pooled connection factory.

30.2 MongoDB

MongoDB is an open-source NoSQL document database that uses a JSON-like schema instead of traditional table-based relational data. Spring Boot offers several conveniences for working with MongoDB, including the spring-boot-starter-data-mongodb and spring-boot-starter-data-mongodb-reactive ‘Starters’.

30.2.1 Connecting to a MongoDB Database

To access Mongo databases, you can inject an auto-configured org.springframework.data.mongodb.MongoDbFactory . By default, the instance tries to connect to a MongoDB server at mongodb://localhost/test The following example shows how to connect to a MongoDB database:

import org.springframework.data.mongodb.MongoDbFactory;
import com.mongodb.DB;
@Component
public class MyBean {
	private final MongoDbFactory mongo;
	@Autowired
	public MyBean(MongoDbFactory mongo) {
		this.mongo = mongo;
	// ...
	public void example() {
		DB db = mongo.getDb();
		// ...
}

You can set the spring.data.mongodb.uri property to change the URL and configure additional settings such as the replica set , as shown in the following example:

spring.data.mongodb.uri=mongodb://user:[email protected]:12345,mongo2.example.com:23456/test

Alternatively, as long as you use Mongo 2.x, you can specify a host / port . For example, you might declare the following settings in your application.properties :

spring.data.mongodb.host=mongoserver
spring.data.mongodb.port=27017

	Note
	If you use the Mongo 3.0 Java driver, `spring.data.mongodb.host` and `spring.data.mongodb.port` are not supported. In such cases, `spring.data.mongodb.uri` should be used to provide all of the configuration.

	Tip
	If `spring.data.mongodb.port` is not specified, the default of `27017` is used. You could delete this line from the example shown earlier.

	Tip
	If you do not use Spring Data Mongo, you can inject `com.mongodb.Mongo` beans instead of using `MongoDbFactory` . You can also declare your own `MongoDbFactory` or `Mongo` bean if you want to take complete control of establishing the MongoDB connection.

30.2.2 MongoTemplate

Spring Data Mongo provides a MongoTemplate class that is very similar in its design to Spring’s JdbcTemplate . As with JdbcTemplate , Spring Boot auto-configures a bean for you to inject the template, as follows:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.stereotype.Component;
@Component
public class MyBean {
	private final MongoTemplate mongoTemplate;
	@Autowired
	public MyBean(MongoTemplate mongoTemplate) {
		this.mongoTemplate = mongoTemplate;
	// ...
}

See the MongoOperations Javadoc for complete details.

30.2.3 Spring Data MongoDB Repositories

Spring Data includes repository support for MongoDB. As with the JPA repositories discussed earlier, the basic principle is that queries are constructed automatically based on method names.

In fact, both Spring Data JPA and Spring Data MongoDB share the same common infrastructure. You could take the JPA example from earlier and, assuming that City is now a Mongo data class rather than a JPA @Entity , it works in the same way, as shown in the following example:

package com.example.myapp.domain;
import org.springframework.data.domain.*;
import org.springframework.data.repository.*;
public interface CityRepository extends Repository<City, Long> {
	Page<City> findAll(Pageable pageable);
	City findByNameAndCountryAllIgnoringCase(String name, String country);
}

	Tip
	You can customize document scanning locations using the `@EntityScan` annotation.

	Tip
	For complete details of Spring Data MongoDB, including its rich object mapping technologies, refer to the reference documentation .

30.2.4 Embedded Mongo

Spring Boot offers auto-configuration for Embedded Mongo . To use it in your Spring Boot application, add a dependency on de.flapdoodle.embed:de.flapdoodle.embed.mongo .

The port that Mongo listens on can be configured by setting the spring.data.mongodb.port property. To use a randomly allocated free port, use a value of 0. The MongoClient created by MongoAutoConfiguration is automatically configured to use the randomly allocated port.

	Note
	If you do not configure a custom port, the embedded support uses a random port (rather than 27017) by default.

If you have SLF4J on the classpath, the output produced by Mongo is automatically routed to a logger named org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongo .

You can declare your own IMongodConfig and IRuntimeConfig beans to take control of the Mongo instance’s configuration and logging routing.

30.3 Neo4j

Neo4j is an open-source NoSQL graph database that uses a rich data model of nodes related by first class relationships, which is better suited for connected big data than traditional rdbms approaches. Spring Boot offers several conveniences for working with Neo4j, including the spring-boot-starter-data-neo4j ‘Starter’.

30.3.1 Connecting to a Neo4j Database

You can inject an auto-configured Neo4jSession , Session , or Neo4jOperations instance as you would any other Spring Bean. By default, the instance tries to connect to a Neo4j server at localhost:7474 . The following example shows how to inject a Neo4j bean:

@Component
public class MyBean {
	private final Neo4jTemplate neo4jTemplate;
	@Autowired
	public MyBean(Neo4jTemplate neo4jTemplate) {
		this.neo4jTemplate = neo4jTemplate;
	// ...
}

You can take full control of the configuration by adding a org.neo4j.ogm.config.Configuration @Bean of your own. Also, adding a @Bean of type Neo4jOperations disables the auto-configuration.

You can configure the user and credentials to use by setting the spring.data.neo4j.* properties, as shown in the following example:

spring.data.neo4j.uri=http://my-server:7474
spring.data.neo4j.username=neo4j
spring.data.neo4j.password=secret

30.3.2 Using the Embedded Mode

If you add org.neo4j:neo4j-ogm-embedded-driver to the dependencies of your application, Spring Boot automatically configures an in-process embedded instance of Neo4j that does not persist any data when your application shuts down. You can explicitly disable that mode by setting spring.data.neo4j.embedded.enabled=false . You can also enable persistence for the embedded mode by providing a path to a database file, as shown in the following example:

	spring.data.neo4j.uri=file://var/tmp/graph.db

	Note
	The Neo4j OGM embedded driver does not provide the Neo4j kernel. Users are expected to provide this dependency manually. See documentation for more details.

30.3.3 Neo4jSession

By default, if you are running a web application, the session is bound to the thread for the entire processing of the request (that is, it uses the "Open Session in View" pattern). If you do not want this behavior, add the following line to your application.properties file:

spring.data.neo4j.open-in-view=false

30.3.4 Spring Data Neo4j Repositories

Spring Data includes repository support for Neo4j.

In fact, both Spring Data JPA and Spring Data Neo4j share the same common infrastructure. You could take the JPA example from earlier and, assuming that City is now a Neo4j OGM @NodeEntity rather than a JPA @Entity , it works in the same way.

	Tip
	You can customize entity scanning locations by using the `@EntityScan` annotation.

To enable repository support (and optionally support for @Transactional ), add the following two annotations to your Spring configuration:

@EnableNeo4jRepositories(basePackages = "com.example.myapp.repository")
@EnableTransactionManagement

30.3.5 Repository Example

The following examples shows an interface definition for a Neo4j repository:

package com.example.myapp.domain;
import org.springframework.data.domain.*;
import org.springframework.data.repository.*;
public interface CityRepository extends GraphRepository<City> {
	Page<City> findAll(Pageable pageable);
	City findByNameAndCountry(String name, String country);
}

	Tip
	For complete details of Spring Data Neo4j, including its rich object mapping technologies, refer to the reference documentation .

30.4 Gemfire

Spring Data Gemfire provides convenient Spring-friendly tools for accessing the Pivotal Gemfire data management platform. There is a spring-boot-starter-data-gemfire ‘Starter’ for collecting the dependencies in a convenient way. There is currently no auto-configuration support for Gemfire, but you can enable Spring Data Repositories with a single annotation: @EnableGemfireRepositories .

30.5 Solr

Apache Solr is a search engine. Spring Boot offers basic auto-configuration for the Solr 5 client library and the abstractions on top of it provided by Spring Data Solr . There is a spring-boot-starter-data-solr ‘Starter’ for collecting the dependencies in a convenient way.

30.5.1 Connecting to Solr

You can inject an auto-configured SolrClient instance as you would any other Spring bean. By default, the instance tries to connect to a server at localhost:8983/solr . The following example shows how to inject a Solr bean:

@Component
public class MyBean {
	private SolrClient solr;
	@Autowired
	public MyBean(SolrClient solr) {
		this.solr = solr;
	// ...
}

If you add your own @Bean of type SolrClient , it replaces the default.

30.5.2 Spring Data Solr Repositories

Spring Data includes repository support for Apache Solr. As with the JPA repositories discussed earlier, the basic principle is that queries are constructed for you automatically based on method names.

In fact, both Spring Data JPA and Spring Data Solr share the same common infrastructure. So you could take the JPA example from earlier and, assuming that City is now a @SolrDocument class rather than a JPA @Entity , it works in the same way.

	Tip
	For complete details of Spring Data Solr, refer to the reference documentation .

30.6 Elasticsearch

Elasticsearch is an open source, distributed, real-time search and analytics engine. Spring Boot offers basic auto-configuration for Elasticsearch and the abstractions on top of it provided by Spring Data Elasticsearch . There is a spring-boot-starter-data-elasticsearch ‘Starter’ for collecting the dependencies in a convenient way. Spring Boot also supports Jest .

30.6.1 Connecting to Elasticsearch by Using Jest

If you have Jest on the classpath, you can inject an auto-configured JestClient targeting localhost:9200 by default. You can further tune how the client is configured, as shown in the following example:

spring.elasticsearch.jest.uris=http://search.example.com:9200
spring.elasticsearch.jest.read-timeout=10000
spring.elasticsearch.jest.username=user
spring.elasticsearch.jest.password=secret

You can also register an arbitrary number of beans that implement HttpClientConfigBuilderCustomizer for more advanced customizations. The following example tunes additional HTTP settings:

static class HttpSettingsCustomizer implements HttpClientConfigBuilderCustomizer {
	@Override
	public void customize(HttpClientConfig.Builder builder) {
		builder.maxTotalConnection(100).defaultMaxTotalConnectionPerRoute(5);
}

To take full control over the registration, define a JestClient bean.

30.6.2 Connecting to Elasticsearch by Using Spring Data

To connect to Elasticsearch, you must provide the address of one or more cluster nodes. The address can be specified by setting the spring.data.elasticsearch.cluster-nodes property to a comma-separated ‘host:port’ list. With this configuration in place, an ElasticsearchTemplate or TransportClient can be injected like any other Spring bean, as shown in the following example:

spring.data.elasticsearch.cluster-nodes=localhost:9300

@Component
public class MyBean {
	private final ElasticsearchTemplate template;
	public MyBean(ElasticsearchTemplate template) {
		this.template = template;
	// ...
}

If you add your own ElasticsearchTemplate or TransportClient @Bean , it replaces the default.

30.6.3 Spring Data Elasticsearch Repositories

Spring Data includes repository support for Elasticsearch. As with the JPA repositories discussed earlier, the basic principle is that queries are constructed for you automatically based on method names.

In fact, both Spring Data JPA and Spring Data Elasticsearch share the same common infrastructure. You could take the JPA example from earlier and, assuming that City is now an Elasticsearch @Document class rather than a JPA @Entity , it works in the same way.

	Tip
	For complete details of Spring Data Elasticsearch, refer to the reference documentation .

30.7 Cassandra

Cassandra is an open source, distributed database management system designed to handle large amounts of data across many commodity servers. Spring Boot offers auto-configuration for Cassandra and the abstractions on top of it provided by Spring Data Cassandra . There is a spring-boot-starter-data-cassandra ‘Starter’ for collecting the dependencies in a convenient way.

30.7.1 Connecting to Cassandra

You can inject an auto-configured CassandraTemplate or a Cassandra Session instance as you would with any other Spring Bean. The spring.data.cassandra.* properties can be used to customize the connection. Generally, you provide keyspace-name and contact-points properties, as shown in the following example:

spring.data.cassandra.keyspace-name=mykeyspace
spring.data.cassandra.contact-points=cassandrahost1,cassandrahost2

The following code listing shows how to inject a Cassandra bean:

@Component
public class MyBean {
	private CassandraTemplate template;
	@Autowired
	public MyBean(CassandraTemplate template) {
		this.template = template;
	// ...
}

If you add your own @Bean of type CassandraTemplate , it replaces the default.

30.7.2 Spring Data Cassandra Repositories

Spring Data includes basic repository support for Cassandra. Currently, this is more limited than the JPA repositories discussed earlier and needs to annotate finder methods with @Query .

	Tip
	For complete details of Spring Data Cassandra, refer to the reference documentation .

30.8 Couchbase

Couchbase is an open-source, distributed multi-model NoSQL document-oriented database that is optimized for interactive applications. Spring Boot offers auto-configuration for Couchbase and the abstractions on top of it provided by Spring Data Couchbase . There are a spring-boot-starter-data-couchbase and spring-boot-starter-data-couchbase-reactive ‘Starters’ for collecting the dependencies in a convenient way.

30.8.1 Connecting to Couchbase

You can get a Bucket and Cluster by adding the Couchbase SDK and some configuration. The spring.couchbase.* properties can be used to customize the connection. Generally, you provide the bootstrap hosts, bucket name, and password, as shown in the following example:

spring.couchbase.bootstrap-hosts=my-host-1,192.168.1.123
spring.couchbase.bucket.name=my-bucket
spring.couchbase.bucket.password=secret

	Tip
	You need to provide at least the bootstrap host(s), in which case the bucket name is `default` and the password is the empty String. Alternatively, you can define your own `org.springframework.data.couchbase.config.CouchbaseConfigurer` `@Bean` to take control over the whole configuration.

It is also possible to customize some of the CouchbaseEnvironment settings. For instance, the following configuration changes the timeout to use to open a new Bucket and enables SSL support:

spring.couchbase.env.timeouts.connect=3000
spring.couchbase.env.ssl.key-store=/location/of/keystore.jks
spring.couchbase.env.ssl.key-store-password=secret

Check the spring.couchbase.env.* properties for more details.

30.8.2 Spring Data Couchbase Repositories

Spring Data includes repository support for Couchbase. For complete details of Spring Data Couchbase, refer to the reference documentation .

You can inject an auto-configured CouchbaseTemplate instance as you would with any other Spring Bean, provided a default CouchbaseConfigurer is available (which happens when you enable Couchbase support, as explained earlier).

The following examples shows how to inject a Couchbase bean:

@Component
public class MyBean {
	private final CouchbaseTemplate template;
	@Autowired
	public MyBean(CouchbaseTemplate template) {
		this.template = template;
	// ...
}

There are a few beans that you can define in your own configuration to override those provided by the auto-configuration:

A CouchbaseTemplate @Bean with a name of couchbaseTemplate .
An IndexManager @Bean with a name of couchbaseIndexManager .
A CustomConversions @Bean with a name of couchbaseCustomConversions .

To avoid hard-coding those names in your own config, you can reuse BeanNames provided by Spring Data Couchbase. For instance, you can customize the converters to use as follows:

@Configuration
public class SomeConfiguration {
	@Bean(BeanNames.COUCHBASE_CUSTOM_CONVERSIONS)
	public CustomConversions myCustomConversions() {
		return new CustomConversions(...);
	// ...
}

	Tip
	If you want to fully bypass the auto-configuration for Spring Data Couchbase, provide your own implementation of `org.springframework.data.couchbase.config.AbstractCouchbaseDataConfiguration` .

30.9 LDAP

LDAP (Lightweight Directory Access Protocol) is an open, vendor-neutral, industry standard application protocol for accessing and maintaining distributed directory information services over an IP network. Spring Boot offers auto-configuration for any compliant LDAP server as well as support for the embedded in-memory LDAP server from UnboundID .

LDAP abstractions are provided by Spring Data LDAP . There is a spring-boot-starter-data-ldap ‘Starter’ for collecting the dependencies in a convenient way.

30.9.1 Connecting to an LDAP Server

To connect to an LDAP server, make sure you declare a dependency on the spring-boot-starter-data-ldap ‘Starter’ or spring-ldap-core and then declare the URLs of your server in your application.properties, as shown in the following example:

spring.ldap.urls=ldap://myserver:1235
spring.ldap.username=admin
spring.ldap.password=secret

If you need to customize connection settings, you can use the spring.ldap.base and spring.ldap.base-environment properties.

30.9.2 Spring Data LDAP Repositories

Spring Data includes repository support for LDAP. For complete details of Spring Data LDAP, refer to the reference documentation .

You can also inject an auto-configured LdapTemplate instance as you would with any other Spring Bean, as shown in the following example:

@Component
public class MyBean {
	private final LdapTemplate template;
	@Autowired
	public MyBean(LdapTemplate template) {
		this.template = template;
	// ...
}

30.9.3 Embedded In-memory LDAP Server

For testing purposes Spring Boot supports auto-configuration of an in-memory LDAP server from UnboundID . To configure the server add a dependency to com.unboundid:unboundid-ldapsdk and declare a base-dn property:

spring.ldap.embedded.base-dn=dc=spring,dc=io

By default, the server starts on a random port and triggers the regular LDAP support. There is no need to specify a spring.ldap.urls property.

If there is a schema.ldif file on your classpath, it is used to initialize the server. If you want to load the initialization script from a different resource, you can also use the spring.ldap.embedded.ldif property.

By default, a standard schema is used to validate LDIF files, you can turn off validation altogether using the spring.ldap.embedded.validation.enabled property. If you have custom attributes, you can use spring.ldap.embedded.validation.schema to define your custom attribute types or object classes.

30.10 InfluxDB

InfluxDB is an open-source time series database optimized for fast, high-availability storage and retrieval of time series data in fields such as operations monitoring, application metrics, Internet-of-Things sensor data, and real-time analytics.

30.10.1 Connecting to InfluxDB

Spring Boot auto-configures an InfluxDB instance, provided the influxdb-java client is on the classpath and the URL of the database is set, as shown in the following example:

spring.influx.url=http://172.0.0.1:8086

If the connection to InfluxDB requires a user and password, you can set the spring.influx.user and spring.influx.password properties accordingly.

InfluxDB relies on OkHttp. If you need to tune the http client InfluxDB uses behind the scenes, you can register an OkHttpClient.Builder bean.

31. Caching

The Spring Framework provides support for transparently adding caching to an application. At its core, the abstraction applies caching to methods, thus reducing the number of executions based on the information available in the cache. The caching logic is applied transparently, without any interference to the invoker. Spring Boot auto-configures the cache infrastructure as long as caching support is enabled via the @EnableCaching annotation.

	Note
	Check the relevant section of the Spring Framework reference for more details.

In a nutshell, adding caching to an operation of your service is as easy as adding the relevant annotation to its method, as shown in the following example:

   import org.springframework.cache.annotation.Cacheable
import org.springframework.stereotype.Component;
@Component
public class MathService {
	@Cacheable("piDecimals")
	public int computePiDecimal(int i) {
		// ...
}

This example demonstrates the use of caching on a potentially costly operation. Before invoking computePiDecimal , the abstraction looks for an entry in the piDecimals cache that matches the i argument. If an entry is found, the content in the cache is immediately returned to the caller, and the method is not invoked. Otherwise, the method is invoked, and the cache is updated before returning the value.

	Caution
	You can also use the standard JSR-107 (JCache) annotations (such as `@CacheResult` ) transparently. However, we strongly advise you to not mix and match the Spring Cache and JCache annotations.

If you do not add any specific cache library, Spring Boot auto-configures a simple provider that uses concurrent maps in memory. When a cache is required (such as piDecimals in the preceding example), this provider creates it for you. The simple provider is not really recommended for production usage, but it is great for getting started and making sure that you understand the features. When you have made up your mind about the cache provider to use, please make sure to read its documentation to figure out how to configure the caches that your application uses. Nearly all providers require you to explicitly configure every cache that you use in the application. Some offer a way to customize the default caches defined by the spring.cache.cache-names property.

	Tip
	It is also possible to transparently update or evict data from the cache.

	Note
	If you use the cache infrastructure with beans that are not interface-based, make sure to enable the `proxyTargetClass` attribute of `@EnableCaching` .

31.1 Supported Cache Providers

The cache abstraction does not provide an actual store and relies on abstraction materialized by the org.springframework.cache.Cache and org.springframework.cache.CacheManager interfaces.

If you have not defined a bean of type CacheManager or a CacheResolver named cacheResolver (see CachingConfigurer ), Spring Boot tries to detect the following providers (in the indicated order):

Generic
JCache (JSR-107) (EhCache 3, Hazelcast, Infinispan, and others)
EhCache 2.x
Hazelcast
Infinispan
Couchbase
Redis
Caffeine
Simple

	Tip
	It is also possible to force a particular cache provider by setting the `spring.cache.type` property. Use this property if you need to disable caching altogether in certain environment (such as tests).

	Tip
	Use the `spring-boot-starter-cache` ‘Starter’ to quickly add basic caching dependencies. The starter brings in `spring-context-support` . If you add dependencies manually, you must include `spring-context-support` in order to use the JCache, EhCache 2.x, or Guava support.

If the CacheManager is auto-configured by Spring Boot, you can further tune its configuration before it is fully initialized by exposing a bean that implements the CacheManagerCustomizer interface. The following example sets a flag to say that null values should be passed down to the underlying map:

@Bean
public CacheManagerCustomizer<ConcurrentMapCacheManager> cacheManagerCustomizer() {
	return new CacheManagerCustomizer<ConcurrentMapCacheManager>() {
		@Override
		public void customize(ConcurrentMapCacheManager cacheManager) {
			cacheManager.setAllowNullValues(false);
}

	Note
	In the example above, an auto-configured `ConcurrentMapCacheManager` is expected. If that is not the case (either you provided your own config or a different cache provider was auto-configured), the customizer is not invoked at all. You can have as many customizers as you want, and you can also order them as usual by using `@Order` or `Ordered` .

31.1.1 Generic

Generic caching is used if the context defines at least one org.springframework.cache.Cache bean. A CacheManager wrapping all beans of that type is created.

31.1.2 JCache (JSR-107)

JCache is bootstrapped via the presence of a javax.cache.spi.CachingProvider on the classpath (that is, a JSR-107 compliant caching library exists on the classpath) and the JCacheCacheManager provided by the spring-boot-starter-cache ‘Starter’. Various compliant libraries are available, and Spring Boot provides dependency management for Ehcache 3, Hazelcast, and Infinispan. Any other compliant library can be added as well.

It might happen that more than one provider is present, in which case the provider must be explicitly specified. Even if the JSR-107 standard does not enforce a standardized way to define the location of the configuration file, Spring Boot does its best to accommodate setting a cache with implementation details, as shown in the following example:

   # Only necessary if more than one provider is present
spring.cache.jcache.provider=com.acme.MyCachingProvider
spring.cache.jcache.config=classpath:acme.xml

	Note
	When a cache library offers both a native implementation and JSR-107 support, Spring Boot prefers the JSR-107 support, so that the same features are available if you switch to a different JSR-107 implementation.

	Tip
	Spring Boot has general support for Hazelcast . If a single `HazelcastInstance` is available, it is automatically reused for the `CacheManager` as well, unless the `spring.cache.jcache.config` property is specified.

There are two ways to customize the underlying javax.cache.cacheManager :

Caches can be created on startup by setting the spring.cache.cache-names property. If a custom javax.cache.configuration.Configuration bean is defined, it is used to customize them.
org.springframework.boot.autoconfigure.cache.JCacheManagerCustomizer beans are invoked with the reference of the CacheManager for full customization.

	Tip
	If a standard `javax.cache.CacheManager` bean is defined, it is wrapped automatically in an `org.springframework.cache.CacheManager` implementation that the abstraction expects. No further customization is applied to it.

31.1.3 EhCache 2.x

EhCache 2.x is used if a file named ehcache.xml can be found at the root of the classpath. If EhCache 2.x is found, the EhCacheCacheManager provided by the spring-boot-starter-cache ‘Starter’ is used to bootstrap the cache manager. An alternate configuration file can be provided as well, as shown in the following example:

spring.cache.ehcache.config=classpath:config/another-config.xml

31.1.4 Hazelcast

Spring Boot has general support for Hazelcast . If a HazelcastInstance has been auto-configured, it is automatically wrapped in a CacheManager .

31.1.5 Infinispan

Infinispan has no default configuration file location, so it must be specified explicitly. Otherwise, the default bootstrap is used.

spring.cache.infinispan.config=infinispan.xml

Caches can be created on startup by setting the spring.cache.cache-names property. If a custom ConfigurationBuilder bean is defined, it is used to customize the caches.

	Note
	The support of Infinispan in Spring Boot is restricted to the embedded mode and is quite basic. If you want more options, you should use the official Infinispan Spring Boot starter instead. See Infinispan’s documentation for more details.

31.1.6 Couchbase

If the Couchbase Java client and the couchbase-spring-cache implementation are available and Couchbase is configured , a CouchbaseCacheManager is auto-configured. It is also possible to create additional caches on startup by setting the spring.cache.cache-names property. These caches operate on the Bucket that was auto-configured. You can also create additional caches on another Bucket by using the customizer. Assume you need two caches ( cache1 and cache2 ) on the "main" Bucket and one cache3 cache with a custom time to live of 2 seconds on the "another" Bucket . You can create the first two caches through configuration, as follows:

spring.cache.cache-names=cache1,cache2

Then you can define a @Configuration class to configure the extra Bucket and the cache3 cache, as follows:

@Configuration
public class CouchbaseCacheConfiguration {
	private final Cluster cluster;
	public CouchbaseCacheConfiguration(Cluster cluster) {
		this.cluster = cluster;
	@Bean
	public Bucket anotherBucket() {
		return this.cluster.openBucket("another", "secret");
	@Bean
	public CacheManagerCustomizer<CouchbaseCacheManager> cacheManagerCustomizer() {
		return c -> {
			c.prepareCache("cache3", CacheBuilder.newInstance(anotherBucket())
					.withExpiration(2));
}

This sample configuration reuses the Cluster that was created via auto-configuration.

31.1.7 Redis

If Redis is available and configured, a RedisCacheManager is auto-configured. It is possible to create additional caches on startup by setting the spring.cache.cache-names property and cache defaults can be configured using spring.cache.redis.* properties. For instance, the following configuration creates cache1 and cache2 caches with a time to live of 10 minutes:

spring.cache.cache-names=cache1,cache2
spring.cache.redis.time-to-live=600000

	Note
	By default, a key prefix is added so that, if two separate caches use the same key, Redis does not have overlapping keys and cannot return invalid values. We strongly recommend keeping this setting enabled if you create your own `RedisCacheManager` .

31.1.8 Caffeine

Caffeine is a Java 8 rewrite of Guava’s cache that supersedes support for Guava. If Caffeine is present, a CaffeineCacheManager (provided by the spring-boot-starter-cache ‘Starter’) is auto-configured. Caches can be created on startup by setting the spring.cache.cache-names property and can be customized by one of the following (in the indicated order):

A cache spec defined by spring.cache.caffeine.spec
A com.github.benmanes.caffeine.cache.CaffeineSpec bean is defined
A com.github.benmanes.caffeine.cache.Caffeine bean is defined

For instance, the following configuration creates cache1 and cache2 caches with a maximum size of 500 and a time to live of 10 minutes

spring.cache.cache-names=cache1,cache2
spring.cache.caffeine.spec=maximumSize=500,expireAfterAccess=600s

If a com.github.benmanes.caffeine.cache.CacheLoader bean is defined, it is automatically associated to the CaffeineCacheManager . Since the CacheLoader is going to be associated with all caches managed by the cache manager, it must be defined as CacheLoader<Object, Object> . The auto-configuration ignores any other generic type.

31.1.9 Simple

If none of the other providers can be found, a simple implementation using a ConcurrentHashMap as the cache store is configured. This is the default if no caching library is present in your application. By default, caches are created as needed, but you can restrict the list of available caches by setting the cache-names property. For instance, if you want only cache1 and cache2 caches, set the cache-names property as follows:

spring.cache.cache-names=cache1,cache2

If you do so and your application uses a cache not listed, then it fails at runtime when the cache is needed, but not on startup. This is similar to the way the "real" cache providers behave if you use an undeclared cache.

31.1.10 None

When @EnableCaching is present in your configuration, a suitable cache configuration is expected as well. If you need to disable caching altogether in certain environments, force the cache type to none to use a no-op implementation, as shown in the following example:

spring.cache.type=none

32. Messaging

The Spring Framework provides extensive support for integrating with messaging systems, from simplified use of the JMS API using JmsTemplate to a complete infrastructure to receive messages asynchronously. Spring AMQP provides a similar feature set for the ‘Advanced Message Queuing Protocol’. Spring Boot also provides auto-configuration options for RabbitTemplate and RabbitMQ. Spring WebSocket natively includes support for STOMP messaging, and Spring Boot has support for that through starters and a small amount of auto-configuration. Spring Boot also has support for Apache Kafka.

32.1 JMS

The javax.jms.ConnectionFactory interface provides a standard method of creating a javax.jms.Connection for interacting with a JMS broker. Although Spring needs a ConnectionFactory to work with JMS, you generally need not use it directly yourself and can instead rely on higher level messaging abstractions. (See the relevant section of the Spring Framework reference documentation for details.) Spring Boot also auto-configures the necessary infrastructure to send and receive messages.

32.1.1 ActiveMQ Support

When ActiveMQ is available on the classpath, Spring Boot can also configure a ConnectionFactory . If the broker is present, an embedded broker is automatically started and configured (provided no broker URL is specified through configuration).

	Note
	If you use `spring-boot-starter-activemq` , the necessary dependencies to connect or embed an ActiveMQ instance are provided, as is the Spring infrastructure to integrate with JMS.

ActiveMQ configuration is controlled by external configuration properties in spring.activemq.* . For example, you might declare the following section in application.properties :

spring.activemq.broker-url=tcp://192.168.1.210:9876
spring.activemq.user=admin
spring.activemq.password=secret

You can also pool JMS resources by adding a dependency to org.apache.activemq:activemq-pool and configuring the PooledConnectionFactory accordingly, as shown in the following example:

spring.activemq.pool.enabled=true
spring.activemq.pool.max-connections=50

	Tip
	See `ActiveMQProperties` for more of the supported options. You can also register an arbitrary number of beans that implement `ActiveMQConnectionFactoryCustomizer` for more advanced customizations.

By default, ActiveMQ creates a destination if it does not yet exist so that destinations are resolved against their provided names.

32.1.2 Artemis Support

Spring Boot can auto-configure a ConnectionFactory when it detects that Artemis is available on the classpath. If the broker is present, an embedded broker is automatically started and configured (unless the mode property has been explicitly set). The supported modes are embedded (to make explicit that an embedded broker is required and that an error should occur if the broker is not available on the classpath) and native (to connect to a broker using the netty transport protocol). When the latter is configured, Spring Boot configures a ConnectionFactory that connects to a broker running on the local machine with the default settings.

	Note
	If you are using `spring-boot-starter-artemis` , the necessary dependencies to connect to an existing Artemis instance are provided, as well as the Spring infrastructure to integrate with JMS. Adding `org.apache.activemq:artemis-jms-server` to your application lets you use embedded mode.

Artemis configuration is controlled by external configuration properties in spring.artemis.* . For example, you might declare the following section in application.properties :

spring.artemis.mode=native
spring.artemis.host=192.168.1.210
spring.artemis.port=9876
spring.artemis.user=admin
spring.artemis.password=secret

When embedding the broker, you can choose if you want to enable persistence and list the destinations that should be made available. These can be specified as a comma-separated list to create them with the default options, or you can define bean(s) of type org.apache.activemq.artemis.jms.server.config.JMSQueueConfiguration or org.apache.activemq.artemis.jms.server.config.TopicConfiguration , for advanced queue and topic configurations, respectively.

See ArtemisProperties for more supported options.

No JNDI lookup is involved, and destinations are resolved against their names, using either the ‘name’ attribute in the Artemis configuration or the names provided through configuration.

32.1.3 Using a JNDI ConnectionFactory

If you are running your application in an application server, Spring Boot tries to locate a JMS ConnectionFactory by using JNDI. By default, the java:/JmsXA and java:/XAConnectionFactory location are checked. You can use the spring.jms.jndi-name property if you need to specify an alternative location, as shown in the following example:

spring.jms.jndi-name=java:/MyConnectionFactory

32.1.4 Sending a Message

Spring’s JmsTemplate is auto-configured, and you can autowire it directly into your own beans, as shown in the following example:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jms.core.JmsTemplate;
import org.springframework.stereotype.Component;
@Component
public class MyBean {
	private final JmsTemplate jmsTemplate;
	@Autowired
	public MyBean(JmsTemplate jmsTemplate) {
		this.jmsTemplate = jmsTemplate;
	// ...
}

	Note
	`JmsMessagingTemplate` can be injected in a similar manner. If a `DestinationResolver` or a `MessageConverter` bean is defined, it is associated automatically to the auto-configured `JmsTemplate` .

32.1.5 Receiving a Message

When the JMS infrastructure is present, any bean can be annotated with @JmsListener to create a listener endpoint. If no JmsListenerContainerFactory has been defined, a default one is configured automatically. If a DestinationResolver or a MessageConverter beans is defined, it is associated automatically to the default factory.

By default, the default factory is transactional. If you run in an infrastructure where a JtaTransactionManager is present, it is associated to the listener container by default. If not, the sessionTransacted flag is enabled. In that latter scenario, you can associate your local data store transaction to the processing of an incoming message by adding @Transactional on your listener method (or a delegate thereof). This ensures that the incoming message is acknowledged, once the local transaction has completed. This also includes sending response messages that have been performed on the same JMS session.

The following component creates a listener endpoint on the someQueue destination:

@Component
public class MyBean {
	@JmsListener(destination = "someQueue")
	public void processMessage(String content) {
		// ...
}

	Tip
	See the Javadoc of `@EnableJms` for more details.

If you need to create more JmsListenerContainerFactory instances or if you want to override the default, Spring Boot provides a DefaultJmsListenerContainerFactoryConfigurer that you can use to initialize a DefaultJmsListenerContainerFactory with the same settings as the one that is auto-configured.

For instance, the following example exposes another factory that uses a specific MessageConverter :

@Configuration
static class JmsConfiguration {
	@Bean
	public DefaultJmsListenerContainerFactory myFactory(
			DefaultJmsListenerContainerFactoryConfigurer configurer) {
		DefaultJmsListenerContainerFactory factory =
				new DefaultJmsListenerContainerFactory();
		configurer.configure(factory, connectionFactory());
		factory.setMessageConverter(myMessageConverter());
		return factory;
}

Then you can use the factory in any @JmsListener -annotated method as follows:

@Component
public class MyBean {
	@JmsListener(destination = "someQueue", containerFactory="myFactory")
	public void processMessage(String content) {
		// ...
}

32.2 AMQP

The Advanced Message Queuing Protocol (AMQP) is a platform-neutral, wire-level protocol for message-oriented middleware. The Spring AMQP project applies core Spring concepts to the development of AMQP-based messaging solutions. Spring Boot offers several conveniences for working with AMQP through RabbitMQ, including the spring-boot-starter-amqp ‘Starter’.

32.2.1 RabbitMQ support

RabbitMQ is a lightweight, reliable, scalable, and portable message broker based on the AMQP protocol. Spring uses RabbitMQ to communicate through the AMQP protocol.

RabbitMQ configuration is controlled by external configuration properties in spring.rabbitmq.* . For example, you might declare the following section in application.properties :

spring.rabbitmq.host=localhost
spring.rabbitmq.port=5672
spring.rabbitmq.username=admin
spring.rabbitmq.password=secret

See RabbitProperties for more of the supported options.

	Tip
	See Understanding AMQP, the protocol used by RabbitMQ for more details.

32.2.2 Sending a Message

Spring’s AmqpTemplate and AmqpAdmin are auto-configured, and you can autowire them directly into your own beans, as shown in the following example:

import org.springframework.amqp.core.AmqpAdmin;
import org.springframework.amqp.core.AmqpTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
@Component
public class MyBean {
	private final AmqpAdmin amqpAdmin;
	private final AmqpTemplate amqpTemplate;
	@Autowired
	public MyBean(AmqpAdmin amqpAdmin, AmqpTemplate amqpTemplate) {
		this.amqpAdmin = amqpAdmin;
		this.amqpTemplate = amqpTemplate;
	// ...
}

	Note
	`RabbitMessagingTemplate` can be injected in a similar manner. If a `MessageConverter` bean is defined, it is associated automatically to the auto-configured `AmqpTemplate` .

If necessary, any org.springframework.amqp.core.Queue that is defined as a bean is automatically used to declare a corresponding queue on the RabbitMQ instance.

To retry operations, you can enable retries on the AmqpTemplate (for example, in the event that the broker connection is lost). Retries are disabled by default.

32.2.3 Receiving a Message

When the Rabbit infrastructure is present, any bean can be annotated with @RabbitListener to create a listener endpoint. If no RabbitListenerContainerFactory has been defined, a default SimpleRabbitListenerContainerFactory is automatically configured and you can switch to a direct container using the spring.rabbitmq.listener.type property. If a MessageConverter or a MessageRecoverer bean is defined, it is automatically associated with the default factory.

The following sample component creates a listener endpoint on the someQueue queue:

@Component
public class MyBean {
	@RabbitListener(queues = "someQueue")
	public void processMessage(String content) {
		// ...
}

	Tip
	See the Javadoc of `@EnableRabbit` for more details.

If you need to create more RabbitListenerContainerFactory instances or if you want to override the default, Spring Boot provides a SimpleRabbitListenerContainerFactoryConfigurer and a DirectRabbitListenerContainerFactoryConfigurer that you can use to initialize a SimpleRabbitListenerContainerFactory and a DirectRabbitListenerContainerFactory with the same settings as the factories used by the auto-configuration.

	Tip
	It does not matter which container type you chose. Those two beans are exposed by the auto-configuration.

For instance, the following configuration class exposes another factory that uses a specific MessageConverter :

@Configuration
static class RabbitConfiguration {
	@Bean
	public SimpleRabbitListenerContainerFactory myFactory(
			SimpleRabbitListenerContainerFactoryConfigurer configurer) {
		SimpleRabbitListenerContainerFactory factory =
				new SimpleRabbitListenerContainerFactory();
		configurer.configure(factory, connectionFactory);
		factory.setMessageConverter(myMessageConverter());
		return factory;
}

Then you can use the factory in any @RabbitListener -annotated method as follows:

@Component
public class MyBean {
	@RabbitListener(queues = "someQueue", containerFactory="myFactory")
	public void processMessage(String content) {
		// ...
}

You can enable retries to handle situations where your listener throws an exception. By default, RejectAndDontRequeueRecoverer is used, but you can define a MessageRecoverer of your own. When retries are exhausted, the message is rejected and either dropped or routed to a dead-letter exchange if the broker is configured to do so. By default, retries are disabled.

Important

By default, if retries are disabled and the listener throws an exception, the delivery is retried indefinitely. You can modify this behavior in two ways: Set the defaultRequeueRejected property to false so that zero re-deliveries are attempted or throw an AmqpRejectAndDontRequeueException to signal the message should be rejected. The latter is the mechanism used when retries are enabled and the maximum delivery attempts are reached.

32.3 Apache Kafka Support

Apache Kafka is supported by providing auto-configuration of the spring-kafka project.

Kafka configuration is controlled by external configuration properties in spring.kafka.* . For example, you might declare the following section in application.properties :

spring.kafka.bootstrap-servers=localhost:9092
spring.kafka.consumer.group-id=myGroup

	Tip
	To create a topic on startup, add a bean of type `NewTopic` . If the topic already exists, the bean is ignored.

See KafkaProperties for more supported options.

32.3.1 Sending a Message

Spring’s KafkaTemplate is auto-configured, and you can autowire it directly in your own beans, as shown in the following example:

@Component
public class MyBean {
	private final KafkaTemplate kafkaTemplate;
	@Autowired
	public MyBean(KafkaTemplate kafkaTemplate) {
		this.kafkaTemplate = kafkaTemplate;
	// ...
}

	Note
	If a `RecordMessageConverter` bean is defined, it is automatically associated to the auto-configured `KafkaTemplate` .

32.3.2 Receiving a Message

When the Apache Kafka infrastructure is present, any bean can be annotated with @KafkaListener to create a listener endpoint. If no KafkaListenerContainerFactory has been defined, a default one is automatically configured with keys defined in spring.kafka.listener.* . Also, if a RecordMessageConverter bean is defined, it is automatically associated to the default factory.

The following component creates a listener endpoint on the someTopic topic:

@Component
public class MyBean {
	@KafkaListener(topics = "someTopic")
	public void processMessage(String content) {
		// ...
}

32.3.3 Additional Kafka Properties

The properties supported by auto configuration are shown in Appendix A, Common application properties . Note that, for the most part, these properties (hyphenated or camelCase) map directly to the Apache Kafka dotted properties. Refer to the Apache Kafka documentation for details.

The first few of these properties apply to both producers and consumers but can be specified at the producer or consumer level if you wish to use different values for each. Apache Kafka designates properties with an importance of HIGH, MEDIUM, or LOW. Spring Boot auto-configuration supports all HIGH importance properties, some selected MEDIUM and LOW properties, and any properties that do not have a default value.

Only a subset of the properties supported by Kafka are available through the KafkaProperties class. If you wish to configure the producer or consumer with additional properties that are not directly supported, use the following properties:

spring.kafka.properties.foo.bar=baz
spring.kafka.consumer.properties.fiz.buz=qux
spring,kafka.producer.properties.baz.qux=fiz

This sets the common foo.bar Kafka property to baz (applies to both producers and consumers), the consumer fiz.buz property to qux and the baz.qux producer property to fiz .

	Important
	Properties set in this way override any configuration item that Spring Boot explicitly supports.

33. Calling REST Services with ‘RestTemplate’

If you need to call remote REST services from your application, you can use the Spring Framework’s RestTemplate class. Since RestTemplate instances often need to be customized before being used, Spring Boot does not provide any single auto-configured RestTemplate bean. It does, however, auto-configure a RestTemplateBuilder , which can be used to create RestTemplate instances when needed. The auto-configured RestTemplateBuilder ensures that sensible HttpMessageConverters are applied to RestTemplate instances.

The following code shows a typical example:

@Service
public class MyService {
	private final RestTemplate restTemplate;
	public MyBean(RestTemplateBuilder restTemplateBuilder) {
		this.restTemplate = restTemplateBuilder.build();
	public Details someRestCall(String name) {
		return this.restTemplate.getForObject("/{name}/details", Details.class, name);
}

	Tip
	`RestTemplateBuilder` includes a number of useful methods that can be used to quickly configure a `RestTemplate` . For example, to add BASIC auth support you can use `builder.basicAuthorization("user", "password").build()` .

33.1 RestTemplate Customization

There are three main approaches to RestTemplate customization, depending on how broadly you want the customizations to apply.

To make the scope of any customizations as narrow as possible, inject the auto-configured RestTemplateBuilder and then call its methods as required. Each method call returns a new RestTemplateBuilder instance, so the customizations only affect this use of the builder.

To make an application-wide, additive customization, use a RestTemplateCustomizer bean. All such beans are automatically registered with the auto-configured RestTemplateBuilder and are applied to any templates that are built with it.

The following example shows a customizer that configures the use of a proxy for all hosts except 192.168.0.5 :

static class ProxyCustomizer implements RestTemplateCustomizer {
	@Override
	public void customize(RestTemplate restTemplate) {
		HttpHost proxy = new HttpHost("proxy.example.com");
		HttpClient httpClient = HttpClientBuilder.create()
				.setRoutePlanner(new DefaultProxyRoutePlanner(proxy) {
					@Override
					public HttpHost determineProxy(HttpHost target,
							HttpRequest request, HttpContext context)
									throws HttpException {
						if (target.getHostName().equals("192.168.0.5")) {
							return null;
						return super.determineProxy(target, request, context);
				}).build();
		restTemplate.setRequestFactory(
				new HttpComponentsClientHttpRequestFactory(httpClient));
}

Finally, the most extreme (and rarely used) option is to create your own RestTemplateBuilder bean. Doing so switches off the auto-configuration of a RestTemplateBuilder and prevents any RestTemplateCustomizer beans from being used.

34. Calling REST Services with ‘WebClient’

If you have Spring WebFlux on your classpath, you can also choose to use WebClient to call remote REST services, Compared to RestTemplate , this client has a more functional feel and is fully reactive. You can create your own client instance with the builder, WebClient.create() . See the relevant section on WebClient .

Spring Boot creates and pre-configures such a builder for you. For example, client HTTP codecs are configured in the same fashion as the server ones (see WebFlux HTTP codecs auto-configuration ).

The following code shows a typical example:

@Service
public class MyService {
	private final WebClient webClient;
	public MyBean(WebClient.Builder webClientBuilder) {
		this.webClient = webClientBuilder.baseUrl("http://example.org").build();
	public Mono<Details> someRestCall(String name) {
		return this.webClient.get().url("/{name}/details", name)
						.retrieve().bodyToMono(Details.class);
}

34.1 WebClient Customization

There are three main approaches to WebClient customization, depending on how broadly you want the customizations to apply.

To make the scope of any customizations as narrow as possible, inject the auto-configured WebClient.Builder and then call its methods as required. WebClient.Builder instances are stateful: Any change on the builder is reflected in all clients subsequently created with it. If you want to create several clients with the same builder, you can also consider cloning the builder with WebClient.Builder other = builder.clone(); .

To make an application-wide, additive customization to all WebClient.Builder instances, you can declare WebClientCustomizer beans and change the WebClient.Builder locally at the point of injection.

Finally, you can fall back to the original API and use WebClient.create() . In that case, no auto-configuration or WebClientCustomizer is applied.

35. Validation

The method validation feature supported by Bean Validation 1.1 is automatically enabled as long as a JSR-303 implementation (such as Hibernate validator) is on the classpath. This lets bean methods be annotated with javax.validation constraints on their parameters and/or on their return value. Target classes with such annotated methods need to be annotated with the @Validated annotation at the type level for their methods to be searched for inline constraint annotations.

For instance, the following service triggers the validation of the first argument, making sure its size is between 8 and 10:

@Service
@Validated
public class MyBean {
	public Archive findByCodeAndAuthor(@Size(min = 8, max = 10) String code,
			Author author) {
}

36. Sending Email

The Spring Framework provides an easy abstraction for sending email by using the JavaMailSender interface, and Spring Boot provides auto-configuration for it as well as a starter module.

	Tip
	See the reference documentation for a detailed explanation of how you can use `JavaMailSender` .

If spring.mail.host and the relevant libraries (as defined by spring-boot-starter-mail ) are available, a default JavaMailSender is created if none exists. The sender can be further customized by configuration items from the spring.mail namespace, see MailProperties for more details.

In particular, certain default timeout values are infinite, and you may want to change that to avoid having a thread blocked by an unresponsive mail server, as shown in the following example:

spring.mail.properties.mail.smtp.connectiontimeout=5000
spring.mail.properties.mail.smtp.timeout=3000
spring.mail.properties.mail.smtp.writetimeout=5000

37. Distributed Transactions with JTA

Spring Boot supports distributed JTA transactions across multiple XA resources by using either an Atomikos or Bitronix embedded transaction manager. JTA transactions are also supported when deploying to a suitable Java EE Application Server.

When a JTA environment is detected, Spring’s JtaTransactionManager is used to manage transactions. Auto-configured JMS, DataSource, and JPA beans are upgraded to support XA transactions. You can use standard Spring idioms, such as @Transactional , to participate in a distributed transaction. If you are within a JTA environment and still want to use local transactions, you can set the spring.jta.enabled property to false to disable the JTA auto-configuration.

37.1 Using an Atomikos Transaction Manager

Atomikos is a popular open source transaction manager which can be embedded into your Spring Boot application. You can use the spring-boot-starter-jta-atomikos Starter to pull in the appropriate Atomikos libraries. Spring Boot auto-configures Atomikos and ensures that appropriate depends-on settings are applied to your Spring beans for correct startup and shutdown ordering.

By default Atomikos transaction logs are written to a transaction-logs directory in your application home directory (the directory in which your application jar file resides). You can customize this directory by setting a spring.jta.log-dir property in your application.properties file. Properties starting with spring.jta.atomikos.properties can also be used to customize the Atomikos UserTransactionServiceImp . See the AtomikosProperties Javadoc for complete details.

Note

To ensure that multiple transaction managers can safely coordinate the same resource managers, each Atomikos instance must be configured with a unique ID. By default, this ID is the IP address of the machine on which Atomikos is running. To ensure uniqueness in production, you should configure the spring.jta.transaction-manager-id property with a different value for each instance of your application.

37.2 Using a Bitronix Transaction Manager

By default, Bitronix transaction log files ( part1.btm and part2.btm ) are written to a transaction-logs directory in your application home directory. You can customize this directory by setting the spring.jta.log-dir property. Properties starting with spring.jta.bitronix.properties are also bound to the bitronix.tm.Configuration bean, allowing for complete customization. See the Bitronix documentation for details.

Note

To ensure that multiple transaction managers can safely coordinate the same resource managers, each Bitronix instance must be configured with a unique ID. By default, this ID is the IP address of the machine on which Bitronix is running. To ensure uniqueness in production, you should configure the spring.jta.transaction-manager-id property with a different value for each instance of your application.

37.3 Using a Narayana Transaction Manager

By default, Narayana transaction logs are written to a transaction-logs directory in your application home directory (the directory in which your application jar file resides). You can customize this directory by setting a spring.jta.log-dir property in your application.properties file. Properties starting with spring.jta.narayana.properties can also be used to customize the Narayana configuration. See the NarayanaProperties Javadoc for complete details.

	Note
	To ensure that multiple transaction managers can safely coordinate the same resource managers, each Narayana instance must be configured with a unique ID. By default, this ID is set to `1` . To ensure uniqueness in production, you should configure the `spring.jta.transaction-manager-id` property with a different value for each instance of your application.

37.4 Using a Java EE Managed Transaction Manager

If you package your Spring Boot application as a war or ear file and deploy it to a Java EE application server, you can use your application server’s built-in transaction manager. Spring Boot tries to auto-configure a transaction manager by looking at common JNDI locations ( java:comp/UserTransaction , java:comp/TransactionManager , and so on). If you use a transaction service provided by your application server, you generally also want to ensure that all resources are managed by the server and exposed over JNDI. Spring Boot tries to auto-configure JMS by looking for a ConnectionFactory at the JNDI path ( java:/JmsXA or java:/XAConnectionFactory ), and you can use the spring.datasource.jndi-name property to configure your DataSource .

37.5 Mixing XA and Non-XA JMS Connections

When using JTA, the primary JMS ConnectionFactory bean is XA aware and participates in distributed transactions. In some situations, you might want to process certain JMS messages using a non-XA ConnectionFactory . For example, your JMS processing logic might take longer than the XA timeout.

If you want to use a non-XA ConnectionFactory , you can inject the nonXaJmsConnectionFactory bean rather than the @Primary jmsConnectionFactory bean. For consistency the jmsConnectionFactory bean is also provided by using the bean alias xaJmsConnectionFactory .

The following example shows how to inject ConnectionFactory instances:

// Inject the primary (XA aware) ConnectionFactory
@Autowired
private ConnectionFactory defaultConnectionFactory;
// Inject the XA aware ConnectionFactory (uses the alias and injects the same as above)
@Autowired
@Qualifier("xaJmsConnectionFactory")
private ConnectionFactory xaConnectionFactory;
// Inject the non-XA aware ConnectionFactory
@Autowired
@Qualifier("nonXaJmsConnectionFactory")
private ConnectionFactory nonXaConnectionFactory;

37.6 Supporting an Alternative Embedded Transaction Manager

The XAConnectionFactoryWrapper and XADataSourceWrapper interfaces can be used to support alternative embedded transaction managers. The interfaces are responsible for wrapping XAConnectionFactory and XADataSource beans and exposing them as regular ConnectionFactory and DataSource beans, which transparently enroll in the distributed transaction. DataSource and JMS auto-configuration use JTA variants, provided you have a JtaTransactionManager bean and appropriate XA wrapper beans registered within your ApplicationContext .

The BitronixXAConnectionFactoryWrapper and BitronixXADataSourceWrapper provide good examples of how to write XA wrappers.

38. Hazelcast

If Hazelcast is on the classpath and a suitable configuration is found, Spring Boot auto-configures a HazelcastInstance that you can inject in your application.

If you define a com.hazelcast.config.Config bean, Spring Boot uses that. If your configuration defines an instance name, Spring Boot tries to locate an existing instance rather than creating a new one.

You could also specify the hazelcast.xml configuration file to use via configuration, as shown in the following example:

spring.hazelcast.config=classpath:config/my-hazelcast.xml

Otherwise, Spring Boot tries to find the Hazelcast configuration from the default locations: hazelcast.xml in the working directory or at the root of the classpath. We also check if the hazelcast.config system property is set. See the Hazelcast documentation for more details.

If hazelcast-client is present on the classpath, Spring Boot first attempts to create a client by checking the following configuration options:

The presence of a com.hazelcast.client.config.ClientConfig bean.
A configuration file defined by the spring.hazelcast.config property.
The presence of the hazelcast.client.config system property.
A hazelcast-client.xml in the working directory or at the root of the classpath.

	Note
	Spring Boot also has explicit caching support for Hazelcast . If caching is enabled, the `HazelcastInstance` is automatically wrapped in a `CacheManager` implementation.

39. Quartz Scheduler

Spring Boot offers several conveniences for working with the Quartz scheduler, including the spring-boot-starter-quartz ‘Starter’. If Quartz is available, a Scheduler is auto-configured (via the SchedulerFactoryBean abstraction).

Beans of the following types are automatically picked up and associated with the Scheduler :

JobDetail : defines a particular Job. JobDetail instances can be built with the JobBuilder API.
Calendar .
Trigger : defines when a particular job is triggered.

By default, an in-memory JobStore is used. However, it is possible to configure a JDBC-based store if a DataSource bean is available in your application and if the spring.quartz.job-store-type property is configured accordingly, as shown in the following example:

spring.quartz.job-store-type=jdbc

When the jdbc store is used, the schema can be initialized on startup, as shown in the following example:

spring.quartz.jdbc.initialize-schema=true

	Note
	By default, the database is detected and initialized by using the standard scripts provided with the Quartz library. It is also possible to provide a custom script by setting the `spring.quartz.jdbc.schema` property.

Quartz Scheduler configuration can be customized by using Quartz configuration properties () spring.quartz.properties.* ) and SchedulerFactoryBeanCustomizer beans, which allow programmatic SchedulerFactoryBean customization.

Jobs can define setters to inject data map properties. Regular beans can also be injected in a similar manner, as shown in the following example:

public class SampleJob extends QuartzJobBean {
	private MyService myService;
	private String name;
	// Inject "MyService" bean
	public void setMyService(MyService myService) { ... }
	// Inject the "name" job data property
	public void setName(String name) { ... }
	@Override
	protected void executeInternal(JobExecutionContext context)
			throws JobExecutionException {
}

40. Spring Integration

Spring Boot offers several conveniences for working with Spring Integration, including the spring-boot-starter-integration ‘Starter’. Spring Integration provides abstractions over messaging and also other transports such as HTTP, TCP, and others. If Spring Integration is available on your classpath, it is initialized through the @EnableIntegration annotation.

Spring Boot also configures some features that are triggered by the presence of additional Spring Integration modules. If 'spring-integration-jmx' is also on the classpath, message processing statistics are published over JMX . If 'spring-integration-jdbc' is available, the default database schema can be created on startup, as shown in the following line:

spring.integration.jdbc.initialize-schema=always

See the IntegrationAutoConfiguration and IntegrationProperties classes for more details.

41. Spring Session

Spring Boot provides Spring Session auto-configuration for a wide range of data stores. When building a Servlet web application, the following stores can be auto-configured:

JDBC
Redis
Hazelcast
MongoDB

When building a reactive web application, the following stores can be auto-configured:

Redis
MongoDB

If Spring Session is available, you must choose the StoreType that you wish to use to store the sessions. For instance, to use JDBC as the back-end store, you can configure your application as follows:

spring.session.store-type=jdbc

	Tip
	You can disable Spring Session by setting the `store-type` to `none` .

Each store has specific additional settings. For instance, it is possible to customize the name of the table for the JDBC store, as shown in the following example:

spring.session.jdbc.table-name=SESSIONS

42. Monitoring and Management over JMX

Java Management Extensions (JMX) provide a standard mechanism to monitor and manage applications. By default, Spring Boot creates an MBeanServer a bean with an ID of ‘mbeanServer’ and exposes any of your beans that are annotated with Spring JMX annotations ( @ManagedResource , @ManagedAttribute , and @ManagedOperation ).

See the JmxAutoConfiguration class for more details.

43. Testing

Spring Boot provides a number of utilities and annotations to help when testing your application. Test support is provided by two modules; spring-boot-test contains core items, and spring-boot-test-autoconfigure supports auto-configuration for tests.

Most developers use the spring-boot-starter-test ‘Starter’, which imports both Spring Boot test modules as well as JUnit, AssertJ, Hamcrest, and a number of other useful libraries.

43.1 Test Scope Dependencies

The spring-boot-starter-test ‘Starter’ (in the test scope )contains the following provided libraries:

JUnit : The de-facto standard for unit testing Java applications.
Spring Test & Spring Boot Test: Utilities and integration test support for Spring Boot applications.
AssertJ : A fluent assertion library.
Hamcrest : A library of matcher objects (also known as constraints or predicates).
Mockito : A Java mocking framework.
JSONassert : An assertion library for JSON.
JsonPath : XPath for JSON.

We generally find these common libraries to be useful when writing tests. If these libraries do not suit your needs, you can add additional test dependencies of your own.

43.2 Testing Spring Applications

One of the major advantages of dependency injection is that it should make your code easier to unit test. You can instantiate objects using the new operator without even involving Spring. You can also use mock objects instead of real dependencies.

Often, you need to move beyond ‘unit testing’ and start ‘integration testing’ (with a Spring ApplicationContext ). It is useful to be able to perform integration testing without requiring deployment of your application or needing to connect to other infrastructure.

The Spring Framework includes a dedicated test module for such integration testing. You can declare a dependency directly to org.springframework:spring-test or use the spring-boot-starter-test ‘Starter’ to pull it in transitively.

If you have not used the spring-test module before, you should start by reading the relevant section of the Spring Framework reference documentation.

43.3 Testing Spring Boot Applications

A Spring Boot application is a Spring ApplicationContext , so nothing very special has to be done to test it beyond what you would normally do with a vanilla Spring context. One thing to watch out for, though, is that the external properties, logging, and other features of Spring Boot are installed in the context by default only if you use SpringApplication to create it.

Spring Boot provides a @SpringBootTest annotation, which can be used as an alternative to the standard spring-test @ContextConfiguration annotation when you need Spring Boot features. The annotation works by creating the ApplicationContext used in your tests through SpringApplication .

You can use the webEnvironment attribute of @SpringBootTest to further refine how your tests run:

MOCK : Loads a WebApplicationContext and provides a mock servlet environment. Embedded servlet containers are not started when using this annotation. If servlet APIs are not on your classpath, this mode transparently falls back to creating a regular non-web ApplicationContext . It can be used in conjunction with @AutoConfigureMockMvc for MockMvc -based testing of your application.
RANDOM_PORT : Loads an ServletWebServerApplicationContext and provides a real servlet environment. Embedded servlet containers are started and listen on a random port.
DEFINED_PORT : Loads a ServletWebServerApplicationContext and provides a real servlet environment. Embedded servlet containers are started and listen on a defined port (from your application.properties or on the default port of 8080 ).
NONE : Loads an ApplicationContext by using SpringApplication but does not provide any servlet environment (mock or otherwise).

	Note
	If your test is `@Transactional` , it rolls back the transaction at the end of each test method by default. However, as using this arrangement with either `RANDOM_PORT` or `DEFINED_PORT` implicitly provides a real servlet environment, the HTTP client and server run in separate threads and, thus, in separate transactions. Any transaction initiated on the server does not roll back in this case.

	Note
	In addition to `@SpringBootTest` , a number of other annotations are also provided for testing more specific slices of an application. You can find more detail later in this document.

	Tip
	Do not forget to add `@RunWith(SpringRunner.class)` to your test. Otherwise, the annotations are ignored.

43.3.1 Detecting Test Configuration

If you are familiar with the Spring Test Framework, you may be used to using @ContextConfiguration(classes=…) in order to specify which Spring @Configuration to load. Alternatively, you might have often used nested @Configuration classes within your test.

When testing Spring Boot applications, this is often not required. Spring Boot’s @*Test annotations search for your primary configuration automatically whenever you do not explicitly define one.

The search algorithm works up from the package that contains the test until it finds a class annotated with @SpringBootApplication or @SpringBootConfiguration . As long as you structured your code in a sensible way, your main configuration is usually found.

	Note
	If you use a annotation to test a more specific slice of your application, you should avoid adding configuration settings that are specific to a particular area on the method’s application class.

If you want to customize the primary configuration, you can use a nested @TestConfiguration class. Unlike a nested @Configuration class, which would be used instead of your application’s primary configuration, a nested @TestConfiguration class is used in addition to your application’s primary configuration.

	Note
	Spring’s test framework caches application contexts between tests. Therefore, as long as your tests share the same configuration (no matter how it’s discovered), the potentially time-consuming process of loading the context happens only once.

43.3.2 Excluding Test Configuration

If your application uses component scanning, for example if you use @SpringBootApplication or @ComponentScan , you may find top-level configuration classes created only for specific tests accidentally get picked up everywhere.

As we have seen earlier , @TestConfiguration can be used on an inner class of a test to customize the primary configuration. When placed on a top-level class, @TestConfiguration indicates that classes in src/test/java should not be picked up by scanning. You can then import that class explicitly where it is required, as shown in the following example:

@RunWith(SpringRunner.class)
@SpringBootTest
@Import(MyTestsConfiguration.class)
public class MyTests {
	@Test
	public void exampleTest() {
}

	Note
	If you directly use `@ComponentScan` (that is, not through `@SpringBootApplication` ) you need to register the `TypeExcludeFilter` with it. See the Javadoc for details.

43.3.3 Working with Random Ports

If you need to start a full running server for tests, we recommend that you use random ports. If you use @SpringBootTest(webEnvironment=WebEnvironment.RANDOM_PORT) , an available port is picked at random each time your test runs.

The @LocalServerPort annotation can be used to inject the actual port used into your test. For convenience, tests that need to make REST calls to the started server can additionally @Autowire a TestRestTemplate , which resolves relative links to the running server, as shown in the following example:

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
import org.springframework.boot.test.web.client.TestRestTemplate;
import org.springframework.test.context.junit4.SpringRunner;
import static org.assertj.core.api.Assertions.assertThat;
@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
public class RandomPortExampleTests {
	@Autowired
	private TestRestTemplate restTemplate;
	@Test
	public void exampleTest() {
		String body = this.restTemplate.getForObject("/", String.class);
		assertThat(body).isEqualTo("Hello World");
}

43.3.4 Mocking and Spying Beans

When running tests, it is sometimes necessary to mock certain components within your application context. For example, you may have a facade over some remote service that is unavailable during development. Mocking can also be useful when you want to simulate failures that might be hard to trigger in a real environment.

Spring Boot includes a @MockBean annotation that can be used to define a Mockito mock for a bean inside your ApplicationContext . You can use the annotation to add new beans or replace a single existing bean definition. The annotation can be used directly on test classes, on fields within your test, or on @Configuration classes and fields. When used on a field, the instance of the created mock is also injected. Mock beans are automatically reset after each test method.

Note

If your test uses one of Spring Boot’s test annotations (such as @SpringBootTest ), this feature is automatically enabled. To use this feature with a different arrangement, a listener need to be explicitly added, as shown in the following example:

@TestExecutionListeners(MockitoTestExecutionListener.class)

The following example replaces an existing RemoteService bean with a mock implementation:

import org.junit.*;
import org.junit.runner.*;
import org.springframework.beans.factory.annotation.*;
import org.springframework.boot.test.context.*;
import org.springframework.boot.test.mock.mockito.*;
import org.springframework.test.context.junit4.*;
import static org.assertj.core.api.Assertions.*;
import static org.mockito.BDDMockito.*;
@RunWith(SpringRunner.class)
@SpringBootTest
public class MyTests {
	@MockBean
	private RemoteService remoteService;
	@Autowired
	private Reverser reverser;
	@Test
	public void exampleTest() {
		// RemoteService has been injected into the reverser bean
		given(this.remoteService.someCall()).willReturn("mock");
		String reverse = reverser.reverseSomeCall();
		assertThat(reverse).isEqualTo("kcom");
}

Additionally, you can use @SpyBean to wrap any existing bean with a Mockito spy . See the Javadoc for full details.

43.3.5 Auto-configured Tests

Spring Boot’s auto-configuration system works well for applications but can sometimes be a little too much for tests. It often helps to load only the parts of the configuration that are required to test a ‘slice’ of your application. For example, you might want to test that Spring MVC controllers are mapping URLs correctly, and you don’t want to involve database calls in those tests, or you might want to test JPA entities, and you are not interested in the web layer when those tests run.

The spring-boot-test-autoconfigure module includes a number of annotations that can be used to automatically configure such ‘slices’. Each of them works in a similar way, providing a @…Test annotation that loads the ApplicationContext and one or more @AutoConfigure… annotations that can be used to customize auto-configuration settings.

	Note
	Each slice loads a very restricted set of auto-configuration classes. If you need to exclude one of them, most `@…Test` annotations provide an `excludeAutoConfiguration` attribute. Alternatively, you can use `@ImportAutoConfiguration#exclude` .

	Tip
	It is also possible to use the `@AutoConfigure…` annotations with the standard `@SpringBootTest` annotation. You can use this combination if you are not interested in ‘slicing’ your application but you want some of the auto-configured test beans.

43.3.6 Auto-configured JSON Tests

To test that object JSON serialization and deserialization is working as expected you can use the @JsonTest annotation. @JsonTest auto-configures the available supported JSON mapper, which can be one of the following libraries:

Jackson ObjectMapper , any @JsonComponent beans and any Jackson Module s
Gson
Jsonb

If you need to configure elements of the auto-configuration, you can use the @AutoConfigureJsonTesters annotation.

Spring Boot includes AssertJ-based helpers that work with the JSONassert and JsonPath libraries to check that JSON is as expected. The JacksonTester , GsonTester , JsonbTester , and BasicJsonTester classes can be used for Jackson, Gson, Jsonb, and Strings respectively. Any helper fields on the test class can be @Autowired when using @JsonTest . The following example shows a test class for Jackson:

import org.junit.*;
import org.junit.runner.*;
import org.springframework.beans.factory.annotation.*;
import org.springframework.boot.test.autoconfigure.json.*;
import org.springframework.boot.test.context.*;
import org.springframework.boot.test.json.*;
import org.springframework.test.context.junit4.*;
import static org.assertj.core.api.Assertions.*;
@RunWith(SpringRunner.class)
@JsonTest
public class MyJsonTests {
	@Autowired
	private JacksonTester<VehicleDetails> json;
	@Test
	public void testSerialize() throws Exception {
		VehicleDetails details = new VehicleDetails("Honda", "Civic");
		// Assert against a `.json` file in the same package as the test
		assertThat(this.json.write(details)).isEqualToJson("expected.json");
		// Or use JSON path based assertions
		assertThat(this.json.write(details)).hasJsonPathStringValue("@.make");
		assertThat(this.json.write(details)).extractingJsonPathStringValue("@.make")
				.isEqualTo("Honda");
	@Test
	public void testDeserialize() throws Exception {
		String content = "{\"make\":\"Ford\",\"model\":\"Focus\"}";
		assertThat(this.json.parse(content))
				.isEqualTo(new VehicleDetails("Ford", "Focus"));
		assertThat(this.json.parseObject(content).getMake()).isEqualTo("Ford");
}

	Note
	JSON helper classes can also be used directly in standard unit tests. Simply call the `initFields` method of the helper in your `@Before` method if you do not use `@JsonTest` .

A list of the auto-configuration that is enabled by @JsonTest can be found in the appendix .

43.3.7 Auto-configured Spring MVC Tests

To test Spring MVC controllers are working as expected, you can use the @WebMvcTest annotation. @WebMvcTest auto-configures the Spring MVC infrastructure and limits scanned beans to @Controller , @ControllerAdvice , @JsonComponent , Converter , GenericConverter , Filter , WebMvcConfigurer , and HandlerMethodArgumentResolver . Regular @Component beans are not scanned when using this annotation.

	Tip
	If you need to register extra components such as Jackson `Module` , you can import additional configuration classes using `@Import` on your test.

Often, @WebMvcTest is limited to a single controller and is used in combination with @MockBean to provide mock implementations for required collaborators.

@WebMvcTest also auto-configures MockMvc . Mock MVC offers a powerful way to quickly test MVC controllers without needing to start a full HTTP server.

	Tip
	You can also auto-configure `MockMvc` in a non- `@WebMvcTest` (such as `@SpringBootTest` ) by annotating it with `@AutoConfigureMockMvc` . The following example uses `MockMvc` :

import org.junit.*;
import org.junit.runner.*;
import org.springframework.beans.factory.annotation.*;
import org.springframework.boot.test.autoconfigure.web.servlet.*;
import org.springframework.boot.test.mock.mockito.*;
import static org.assertj.core.api.Assertions.*;
import static org.mockito.BDDMockito.*;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.*;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;
@RunWith(SpringRunner.class)
@WebMvcTest(UserVehicleController.class)
public class MyControllerTests {
	@Autowired
	private MockMvc mvc;
	@MockBean
	private UserVehicleService userVehicleService;
	@Test
	public void testExample() throws Exception {
		given(this.userVehicleService.getVehicleDetails("sboot"))
				.willReturn(new VehicleDetails("Honda", "Civic"));
		this.mvc.perform(get("/sboot/vehicle").accept(MediaType.TEXT_PLAIN))
				.andExpect(status().isOk()).andExpect(content().string("Honda Civic"));
}

	Tip
	If you need to configure elements of the auto-configuration (for example, when servlet filters should be applied) you can use attributes in the `@AutoConfigureMockMvc` annotation.

If you use HtmlUnit or Selenium, auto-configuration also provides an HTMLUnit WebClient bean and/or a WebDriver bean. The following example uses HtmlUnit:

import com.gargoylesoftware.htmlunit.*;
import org.junit.*;
import org.junit.runner.*;
import org.springframework.beans.factory.annotation.*;
import org.springframework.boot.test.autoconfigure.web.servlet.*;
import org.springframework.boot.test.mock.mockito.*;
import static org.assertj.core.api.Assertions.*;
import static org.mockito.BDDMockito.*;
@RunWith(SpringRunner.class)
@WebMvcTest(UserVehicleController.class)
public class MyHtmlUnitTests {
	@Autowired
	private WebClient webClient;
	@MockBean
	private UserVehicleService userVehicleService;
	@Test
	public void testExample() throws Exception {
		given(this.userVehicleService.getVehicleDetails("sboot"))
				.willReturn(new VehicleDetails("Honda", "Civic"));
		HtmlPage page = this.webClient.getPage("/sboot/vehicle.html");
		assertThat(page.getBody().getTextContent()).isEqualTo("Honda Civic");
}

	Note
	By default, Spring Boot puts `WebDriver` beans in a special “scope” to ensure that the driver is quit after each test and that a new instance is injected. If you do not want this behavior, you can add `@Scope("singleton")` to your `WebDriver` `@Bean` definition.

A list of the auto-configuration settings that are enabled by @WebMvcTest can be found in the appendix .

43.3.8 Auto-configured Spring WebFlux Tests

To test that Spring WebFlux controllers are working as expected, you can use the @WebFluxTest annotation. @WebFluxTest auto-configures the Spring WebFlux infrastructure and limits scanned beans to @Controller , @ControllerAdvice , @JsonComponent , Converter , GenericConverter , and WebFluxConfigurer . Regular @Component beans are not scanned when the @WebFluxTest annotation is used.

	Tip
	If you need to register extra components such as Jackson `Module` , you can import additional configuration classes using `@Import` on your test.

Often, @WebFluxTest is limited to a single controller and used in combination with the @MockBean annotation to provide mock implementations for required collaborators.

@WebFluxTest also auto-configures WebTestClient , which offers a powerful way to quickly test WebFlux controllers without needing to start a full HTTP server.

	Tip
	You can also auto-configure `WebTestClient` in a non- `@WebFluxTest` (such as `@SpringBootTest` ) by annotating it with `@AutoConfigureWebTestClient` . The following example shows a class that uses both `@WebFluxTest` and a `WebTestClient` :

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.reactive.WebFluxTest;
import org.springframework.http.MediaType;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.test.web.reactive.server.WebTestClient;
@RunWith(SpringRunner.class)
@WebFluxTest(UserVehicleController.class)
public class MyControllerTests {
	@Autowired
	private WebTestClient webClient;
	@MockBean
	private UserVehicleService userVehicleService;
	@Test
	public void testExample() throws Exception {
		given(this.userVehicleService.getVehicleDetails("sboot"))
				.willReturn(new VehicleDetails("Honda", "Civic"));
		this.webClient.get().uri("/sboot/vehicle").accept(MediaType.TEXT_PLAIN)
				.exchange()
				.expectStatus().isOk()
				.expectBody(String.class).isEqualTo("Honda Civic");
}

A list of the auto-configuration that is enabled by @WebFluxTest can be found in the appendix .

43.3.9 Auto-configured Data JPA Tests

You can use the @DataJpaTest annotation to test JPA applications. By default, it configures an in-memory embedded database, scans for @Entity classes, and configures Spring Data JPA repositories. Regular @Component beans are not loaded into the ApplicationContext .

By default, data JPA tests are transactional and roll back at the end of each test. See the relevant section in the Spring Framework Reference Documentation for more details. If that is not what you want, you can disable transaction management for a test or for the whole class as follows:

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
@RunWith(SpringRunner.class)
@DataJpaTest
@Transactional(propagation = Propagation.NOT_SUPPORTED)
public class ExampleNonTransactionalTests {
}

Data JPA tests may also inject a TestEntityManager bean, which provides an alternative to the standard JPA EntityManager that is specifically designed for tests. If you want to use TestEntityManager outside of @DataJpaTest instances, you can also use the @AutoConfigureTestEntityManager annotation. A JdbcTemplate is also available if you need that. The following example shows the @DataJpaTest annotation in use:

import org.junit.*;
import org.junit.runner.*;
import org.springframework.boot.test.autoconfigure.orm.jpa.*;
import static org.assertj.core.api.Assertions.*;
@RunWith(SpringRunner.class)
@DataJpaTest
public class ExampleRepositoryTests {
	@Autowired
	private TestEntityManager entityManager;
	@Autowired
	private UserRepository repository;
	@Test
	public void testExample() throws Exception {
		this.entityManager.persist(new User("sboot", "1234"));
		User user = this.repository.findByUsername("sboot");
		assertThat(user.getUsername()).isEqualTo("sboot");
		assertThat(user.getVin()).isEqualTo("1234");
}

In-memory embedded databases generally work well for tests, since they are fast and do not require any installation. If, however, you prefer to run tests against a real database you can use the @AutoConfigureTestDatabase annotation, as shown in the following example:

@RunWith(SpringRunner.class)
@DataJpaTest
@AutoConfigureTestDatabase(replace=Replace.NONE)
public class ExampleRepositoryTests {
	// ...
}

A list of the auto-configuration settings that are enabled by @DataJpaTest can be found in the appendix .

43.3.10 Auto-configured JDBC Tests

@JdbcTest is similar to @DataJpaTest but for pure JDBC-related tests. By default, it also configures an in-memory embedded database and a JdbcTemplate . Regular @Component beans are not loaded into the ApplicationContext .

By default, JDBC tests are transactional and roll back at the end of each test. See the relevant section in the Spring Framework Reference Documentation for more details. If that is not what you want, you can disable transaction management for a test or for the whole class as follows:

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.autoconfigure.jdbc.JdbcTest;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
@RunWith(SpringRunner.class)
@JdbcTest
@Transactional(propagation = Propagation.NOT_SUPPORTED)
public class ExampleNonTransactionalTests {
}

If you prefer your test to run against a real database, you can use the @AutoConfigureTestDatabase annotation in the same way as for DataJpaTest . (See Section 43.3.9, “Auto-configured Data JPA Tests” .)

A list of the auto-configuration that is enabled by @JdbcTest can be found in the appendix .

43.3.11 Auto-configured jOOQ Tests

You can use @JooqTest in a similar fashion as @JdbcTest but for jOOQ-related tests. As jOOQ relies heavily on a Java-based schema that corresponds with the database schema, the existing DataSource is used. If you want to replace it with an in-memory database, you can use @AutoconfigureTestDatabase to override those settings.

@JooqTest configures a DSLContext . Regular @Component beans are not loaded into the ApplicationContext . The following example shows the @JooqTest annotation in use:

import org.jooq.DSLContext;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.autoconfigure.jooq.JooqTest;
import org.springframework.test.context.junit4.SpringRunner;
@RunWith(SpringRunner.class)
@JooqTest
public class ExampleJooqTests {
	@Autowired
	private DSLContext dslContext;
}

JOOQ tests are transactional and roll back at the end of each test by default. If that is not what you want, you can disable transaction management for a test or for the whole test class as shown in the JDBC example .

A list of the auto-configuration that is enabled by @JooqTest can be found in the appendix .

43.3.12 Auto-configured Data MongoDB Tests

You can use @DataMongoTest to test MongoDB applications. By default, it configures an in-memory embedded MongoDB (if available), configures a MongoTemplate , scans for @Document classes, and configures Spring Data MongoDB repositories. Regular @Component beans are not loaded into the ApplicationContext . The following class shows the @DataMongoTest annotation in use:

import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.data.mongo.DataMongoTest;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.test.context.junit4.SpringRunner;
@RunWith(SpringRunner.class)
@DataMongoTest
public class ExampleDataMongoTests {
	@Autowired
	private MongoTemplate mongoTemplate;
}

In-memory embedded MongoDB generally works well for tests, since it is fast and does not require any developer installation. If, however, you prefer to run tests against a real MongoDB server, you should exclude the embedded MongoDB auto-configuration, as shown in the following example:

import org.junit.runner.RunWith;
 import org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongoAutoConfiguration;
import org.springframework.boot.test.autoconfigure.data.mongo.DataMongoTest;
import org.springframework.test.context.junit4.SpringRunner;
@RunWith(SpringRunner.class)
@DataMongoTest(excludeAutoConfiguration = EmbeddedMongoAutoConfiguration.class)
public class ExampleDataMongoNonEmbeddedTests {
}

A list of the auto-configuration settings that are enabled by @DataMongoTest can be found in the appendix .

43.3.13 Auto-configured Data Neo4j Tests

You can use @DataNeo4jTest to test Neo4j applications. By default, it uses an in-memory embedded Neo4j (if the embedded driver is available), scans for @NodeEntity classes, and configures Spring Data Neo4j repositories. Regular @Component beans are not loaded into the ApplicationContext :

import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.data.neo4j.DataNeo4jTest;
import org.springframework.test.context.junit4.SpringRunner;
@RunWith(SpringRunner.class)
@DataNeo4jTest
public class ExampleDataNeo4jTests {
	@Autowired
	private YourRepository repository;
}

By default, Data Neo4j tests are transactional and roll back at the end of each test. See the relevant section in the Spring Framework Reference Documentation for more details. If that is not what you want, you can disable transaction management for a test or for the whole class as follows:

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.autoconfigure.data.neo4j.DataNeo4jTest;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
@RunWith(SpringRunner.class)
@DataNeo4jTest
@Transactional(propagation = Propagation.NOT_SUPPORTED)
public class ExampleNonTransactionalTests {
}

A list of the auto-configuration settings that are enabled by @DataNeo4jTest can be found in the appendix .

43.3.14 Auto-configured Data Redis Tests

You can use @DataRedisTest to test Redis applications. By default, it scans for @RedisHash classes and configures Spring Data Redis repositories. Regular @Component beans are not loaded into the ApplicationContext . The following example shows the @DataRedisTest annotation in use:

import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.data.redis.DataRedisTest;
import org.springframework.test.context.junit4.SpringRunner;
@RunWith(SpringRunner.class)
@DataRedisTest
public class ExampleDataRedisTests {
	@Autowired
	private YourRepository repository;
}

A list of the auto-configuration settings that are enabled by @DataRedisTest can be found in the appendix .

43.3.15 Auto-configured Data LDAP Tests

You can use @DataLdapTest to test LDAP applications. By default, it configures an in-memory embedded LDAP (if available), configures an LdapTemplate , scans for @Entry classes, and configures Spring Data LDAP repositories. Regular @Component beans are not loaded into the ApplicationContext . The following example shows the @DataLdapTest annotation in use:

import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.data.ldap.DataLdapTest;
import org.springframework.ldap.core.LdapTemplate;
import org.springframework.test.context.junit4.SpringRunner;
@RunWith(SpringRunner.class)
@DataLdapTest
public class ExampleDataLdapTests {
	@Autowired
	private LdapTemplate ldapTemplate;
}

In-memory embedded LDAP generally works well for tests, since it is fast and does not require any developer installation. If, however, you prefer to run tests against a real LDAP server, you should exclude the embedded LDAP auto-configuration, as shown in the following example:

import org.junit.runner.RunWith;
import org.springframework.boot.autoconfigure.ldap.embedded.EmbeddedLdapAutoConfiguration;
import org.springframework.boot.test.autoconfigure.data.ldap.DataLdapTest;
import org.springframework.test.context.junit4.SpringRunner;
@RunWith(SpringRunner.class)
@DataLdapTest(excludeAutoConfiguration = EmbeddedLdapAutoConfiguration.class)
public class ExampleDataLdapNonEmbeddedTests {
}

A list of the auto-configuration settings that are enabled by @DataLdapTest can be found in the appendix .

43.3.16 Auto-configured REST Clients

You can use the @RestClientTest annotation to test REST clients. By default, it auto-configures Jackson, GSON, and Jsonb support, configures a RestTemplateBuilder , and adds support for MockRestServiceServer . The specific beans that you want to test should be specified by using the value or components attribute of @RestClientTest , as shown in the following example:

@RunWith(SpringRunner.class)
@RestClientTest(RemoteVehicleDetailsService.class)
public class ExampleRestClientTest {
	@Autowired
	private RemoteVehicleDetailsService service;
	@Autowired
	private MockRestServiceServer server;
	@Test
	public void getVehicleDetailsWhenResultIsSuccessShouldReturnDetails()
			throws Exception {
		this.server.expect(requestTo("/greet/details"))
				.andRespond(withSuccess("hello", MediaType.TEXT_PLAIN));
		String greeting = this.service.callRestService();
		assertThat(greeting).isEqualTo("hello");
}

A list of the auto-configuration settings that are enabled by @RestClientTest can be found in the appendix .

43.3.17 Auto-configured Spring REST Docs Tests

You can use the @AutoConfigureRestDocs annotation to use Spring REST Docs in your tests with Mock MVC or REST Assured. It removes the need for the JUnit rule in Spring REST Docs.

@AutoConfigureRestDocs can be used to override the default output directory ( target/generated-snippets if you are using Maven or build/generated-snippets if you are using Gradle). It can also be used to configure the host, scheme, and port that appears in any documented URIs.

Auto-configured Spring REST Docs Tests with Mock MVC

@AutoConfigureRestDocs customizes the MockMvc bean to use Spring REST Docs. You can inject it by using @Autowired and use it in your tests as you normally would when using Mock MVC and Spring REST Docs, as shown in the following example:

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
import org.springframework.http.MediaType;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.test.web.servlet.MockMvc;
import static org.springframework.restdocs.mockmvc.MockMvcRestDocumentation.document;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;
@RunWith(SpringRunner.class)
@WebMvcTest(UserController.class)
@AutoConfigureRestDocs
public class UserDocumentationTests {
	@Autowired
	private MockMvc mvc;
	@Test
	public void listUsers() throws Exception {
		this.mvc.perform(get("/users").accept(MediaType.TEXT_PLAIN))
				.andExpect(status().isOk())
				.andDo(document("list-users"));
}

If you require more control over Spring REST Docs configuration than offered by the attributes of @AutoConfigureRestDocs , a RestDocsMockMvcConfigurationCustomizer bean can be used, as shown in the following example:

@TestConfiguration
static class CustomizationConfiguration
		implements RestDocsMockMvcConfigurationCustomizer {
	@Override
	public void customize(MockMvcRestDocumentationConfigurer configurer) {
		configurer.snippets().withTemplateFormat(TemplateFormats.markdown());
}

If you want to make use of Spring REST Docs support for a parameterized output directory, you can create a RestDocumentationResultHandler bean. The auto-configuration calls alwaysDo with this result handler, thereby causing each MockMvc call to automatically generate the default snippets. The following example shows a RestDocumentationResultHandler being defined:

@TestConfiguration
static class ResultHandlerConfiguration {
	@Bean
	public RestDocumentationResultHandler restDocumentation() {
		return MockMvcRestDocumentation.document("{method-name}");
}

Auto-configured Spring REST Docs Tests with REST Assured

@AutoConfigureRestDocs makes a RequestSpecification bean, preconfigured to use Spring REST Docs, available to your tests. You can inject it by using @Autowired and use it in your tests as you normally would when using REST Assured and Spring REST Docs, as shown in the following example:

import io.restassured.specification.RequestSpecification;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.restdocs.AutoConfigureRestDocs;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
import org.springframework.boot.web.server.LocalServerPort;
import org.springframework.test.context.junit4.SpringRunner;
import static io.restassured.RestAssured.given;
import static org.hamcrest.CoreMatchers.is;
import static org.springframework.restdocs.restassured3.RestAssuredRestDocumentation.document;
@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
@AutoConfigureRestDocs
public class UserDocumentationTests {
	@LocalServerPort
	private int port;
	@Autowired
	private RequestSpecification documentationSpec;
	@Test
	public void listUsers() throws Exception {
		given(this.documentationSpec).filter(document("list-users")).when()
				.port(this.port).get("/").then().assertThat().statusCode(is(200));
}

If you require more control over Spring REST Docs configuration than offered by the attributes of @AutoConfigureRestDocs , a RestDocsRestAssuredConfigurationCustomizer bean can be used, as shown in the following example:

@TestConfiguration
public static class CustomizationConfiguration
		implements RestDocsRestAssuredConfigurationCustomizer {
	@Override
	public void customize(RestAssuredRestDocumentationConfigurer configurer) {
		configurer.snippets().withTemplateFormat(TemplateFormats.markdown());
}

43.3.18 User Configuration and Slicing

If you structure your code in a sensible way, your @SpringBootApplication class is used by default as the configuration of your tests.

It then becomes important not to litter the application’s main class with configuration settings that are specific to a particular area of its functionality.

Assume that you are using Spring Batch and you rely on the auto-configuration for it. You could define your @SpringBootApplication as follows:

@SpringBootApplication
@EnableBatchProcessing
public class SampleApplication { ... }

Because this class is the source configuration for the test, any slice test actually tries to start Spring Batch, which is definitely not what you want to do. A recommended approach is to move that area-specific configuration to a separate @Configuration class at the same level as your application, as shown in the following example:

@Configuration
@EnableBatchProcessing
public class BatchConfiguration { ... }

	Note
	Depending on the complexity of your application, you may either have a single `@Configuration` class for your customizations or one class per domain area when it makes sense. The latter approach lets you enable it in one of your tests, if necessary, with the `@Import` annotation.

Another source of confusion is classpath scanning. Assume that, while you structured your code in a sensible way, you need to scan an additional package. Your application may resemble the following code:

@SpringBootApplication
@ComponentScan({ "com.example.app", "org.acme.another" })
public class SampleApplication { ... }

This effectively overrides the default component scan directive with the side effect of scanning those two packages regardless of the slice that you chose. For instance, a @DataJpaTest seems to suddenly scan components and user configurations of your application. Again, moving the custom directive to a separate class is a good way to fix this issue.

	Tip
	If this is not an option for you, you can create a `@SpringBootConfiguration` somewhere in the hierarchy of your test so that it is used instead. Alternatively, you can specify a source for your test, which disables the behavior of finding a default one.

43.3.19 Using Spock to Test Spring Boot Applications

If you wish to use Spock to test a Spring Boot application, you should add a dependency on Spock’s spock-spring module to your application’s build. spock-spring integrates Spring’s test framework into Spock. It is recommended that you use Spock 1.1 or later to benefit from a number of improvements to Spock’s Spring Framework and Spring Boot integration. See the documentation for Spock’s Spring module for further details.

43.4 Test Utilities

A few test utility classes that are generally useful when testing your application are packaged as part of spring-boot .

43.4.1 ConfigFileApplicationContextInitializer

ConfigFileApplicationContextInitializer is an ApplicationContextInitializer that you can apply to your tests to load Spring Boot application.properties files. You can use it when you do not need the full set of features provided by @SpringBootTest .

@ContextConfiguration(classes = Config.class,
	initializers = ConfigFileApplicationContextInitializer.class)

	Note
	Using `ConfigFileApplicationContextInitializer` alone does not provide support for `@Value("${…}")` injection. Its only job is to ensure that `application.properties` files are loaded into Spring’s `Environment` . For `@Value` support, you need to either additionally configure a `PropertySourcesPlaceholderConfigurer` or use `@SpringBootTest` , where one will be auto-configured for you.

43.4.2 EnvironmentTestUtils

EnvironmentTestUtils lets you quickly add properties to a ConfigurableEnvironment or ConfigurableApplicationContext . You can call it with key=value strings, as follows:

EnvironmentTestUtils.addEnvironment(env, "org=Spring", "name=Boot");

43.4.3 OutputCapture

OutputCapture is a JUnit Rule that you can use to capture System.out and System.err output. You can declare the capture as a @Rule and then use toString() for assertions, as follows:

import org.junit.Rule;
import org.junit.Test;
import org.springframework.boot.test.rule.OutputCapture;
import static org.hamcrest.Matchers.*;
import static org.junit.Assert.*;
public class MyTest {
	@Rule
	public OutputCapture capture = new OutputCapture();
	@Test
	public void testName() throws Exception {
		System.out.println("Hello World!");
		assertThat(capture.toString(), containsString("World"));
}

43.4.4 TestRestTemplate

TestRestTemplate is a convenience alternative to Spring’s RestTemplate that is useful in integration tests. You can get a vanilla template or one that sends Basic HTTP authentication (with a username and password). In either case, the template behaves in a test-friendly way by not throwing exceptions on server-side errors. It is recommended, but not mandatory, to use the Apache HTTP Client (version 4.3.2 or better). If you have that on your classpath, the TestRestTemplate responds by configuring the client appropriately. If you do use Apache’s HTTP client, some additional test-friendly features are enabled:

Redirects are not followed (so you can assert the response location).
Cookies are ignored (so the template is stateless).

TestRestTemplate can be instantiated directly in your integration tests, as shown in the following example:

public class MyTest {
	private TestRestTemplate template = new TestRestTemplate();
	@Test
	public void testRequest() throws Exception {
		HttpHeaders headers = template.getForEntity("http://myhost.com/example", String.class).getHeaders();
		assertThat(headers.getLocation().toString(), containsString("myotherhost"));
}

Alternatively, if you use the @SpringBootTest annotation with WebEnvironment.RANDOM_PORT or WebEnvironment.DEFINED_PORT , you can just inject a fully configured TestRestTemplate and start using it. If necessary, additional customizations can be applied through the RestTemplateBuilder bean. Any URLs that do not specify a host and port automatically connect to the embedded server, as shown in the following example:

@RunWith(SpringRunner.class)
@SpringBootTest
public class MyTest {
	@Autowired
	private TestRestTemplate template;
	@Test
	public void testRequest() throws Exception {
		HttpHeaders headers = template.getForEntity("/example", String.class).getHeaders();
		assertThat(headers.getLocation().toString(), containsString("myotherhost"));
	@TestConfiguration
	static class Config {
		@Bean
		public RestTemplateBuilder restTemplateBuilder() {
			return new RestTemplateBuilder()
				.additionalMessageConverters(...)
				.customizers(...);
}

44. WebSockets

Spring Boot provides WebSockets auto-configuration for embedded Tomcat 8.5, Jetty 9, and Undertow. If you deploy a war file to a standalone container, Spring Boot assumes that the container is responsible for the configuration of its WebSocket support.

Spring Framework provides rich WebSocket support that can be easily accessed through the spring-boot-starter-websocket module.

45. Web Services

Spring Boot provides Web Services auto-configuration so that all you must do is define your Endpoints .

The Spring Web Services features can be easily accessed with the spring-boot-starter-webservices module.

SimpleWsdl11Definition and SimpleXsdSchema beans can be automatically created for your WSDLs and XSDs respectively. To do so, configure their location, as shown in the following example:

spring.webservices.wsdl-locations=classpath:/wsdl

46. Creating Your Own Auto-configuration

If you work in a company that develops shared libraries, or if you work on an open-source or commercial library, you might want to develop your own auto-configuration. Auto-configuration classes can be bundled in external jars and still be picked-up by Spring Boot.

Auto-configuration can be associated to a "starter" that provides the auto-configuration code as well as the typical libraries that you would use with it. We first cover what you need to know to build your own auto-configuration and then we move on to the typical steps required to create a custom starter .

	Tip
	A demo project is available to showcase how you can create a starter step-by-step.

46.1 Understanding Auto-configured Beans

Under the hood, auto-configuration is implemented with standard @Configuration classes. Additional @Conditional annotations are used to constrain when the auto-configuration should apply. Usually, auto-configuration classes use @ConditionalOnClass and @ConditionalOnMissingBean annotations. This ensures that auto-configuration applies only when relevant classes are found and when you have not declared your own @Configuration .

You can browse the source code of spring-boot-autoconfigure to see the @Configuration classes that we provide (see the META-INF/spring.factories file).

46.2 Locating Auto-configuration Candidates

Spring Boot checks for the presence of a META-INF/spring.factories file within your published jar. The file should list your configuration classes under the EnableAutoConfiguration key, as shown in the following example:

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.mycorp.libx.autoconfigure.LibXAutoConfiguration,\
com.mycorp.libx.autoconfigure.LibXWebAutoConfiguration

You can use the @AutoConfigureAfter or @AutoConfigureBefore annotations if your configuration needs to be applied in a specific order. For example, if you provide web-specific configuration, your class may need to be applied after WebMvcAutoConfiguration .

If you want to order certain auto-configurations that should not have any direct knowledge of each other, you can also use @AutoConfigureOrder . That annotation has the same semantic as the regular @Order annotation but provides a dedicated order for auto-configuration classes.

	Note
	Auto-configurations must be loaded that way only . Make sure that they are defined in a specific package space and that, in particular, they are never the target of component scanning.

46.3 Condition Annotations

You almost always want to include one or more @Conditional annotations on your auto-configuration class. The @ConditionalOnMissingBean annotation is one common example that is used to allow developers to ‘override’ auto-configuration if they are not happy with your defaults.

Spring Boot includes a number of @Conditional annotations that you can reuse in your own code by annotating @Configuration classes or individual @Bean methods. These annotations include:

Section 46.3.1, “Class Conditions”
Section 46.3.2, “Bean Conditions”
Section 46.3.3, “Property Conditions”
Section 46.3.4, “Resource Conditions”
Section 46.3.5, “Web Application Conditions”
Section 46.3.6, “SpEL Expression Conditions”

46.3.1 Class Conditions

The @ConditionalOnClass and @ConditionalOnMissingClass annotations let configuration be included based on the presence or absence of specific classes. Due to the fact that annotation metadata is parsed by using ASM , you can use the value attribute to refer to the real class, even though that class might not actually appear on the running application classpath. You can also use the name attribute if you prefer to specify the class name by using a String value.

	Tip
	If you use `@ConditionalOnClass` or `@ConditionalOnMissingClass` as a part of a meta-annotation to compose your own composed annotations, you must use `name` as referring to the class in such a case is not handled.

46.3.2 Bean Conditions

The @ConditionalOnBean and @ConditionalOnMissingBean annotations let a bean be included based on the presence or absence of specific beans. You can use the value attribute to specify beans by type or name to specify beans by name. The search attribute lets you limit the ApplicationContext hierarchy that should be considered when searching for beans.

When placed on a @Bean method, the target type defaults to the return type of the method, as shown in the following example:

@Configuration
public class MyAutoConfiguration {
	@Bean
	@ConditionalOnMissingBean
	public MyService myService() { ... }
}

In the preceding example, the myService bean is going to be created if no bean of type MyService is already contained in the ApplicationContext .

	Tip
	You need to be very careful about the order that bean definitions are added as these conditions are evaluated based on what has been processed so far. For this reason, we recommend only using `@ConditionalOnBean` and `@ConditionalOnMissingBean` annotations on auto-configuration classes (since these are guaranteed to load after any user-defined bean definitions have been added).

	Note
	`@ConditionalOnBean` and `@ConditionalOnMissingBean` do not prevent `@Configuration` classes from being created. Using these conditions at the class level is equivalent to marking each contained `@Bean` method with the annotation.

46.3.3 Property Conditions

The @ConditionalOnProperty annotation lets configuration be included based on a Spring Environment property. Use the prefix and name attributes to specify the property that should be checked. By default, any property that exists and is not equal to false is matched. You can also create more advanced checks by using the havingValue and matchIfMissing attributes.

46.3.4 Resource Conditions

The @ConditionalOnResource annotation lets configuration be included only when a specific resource is present. Resources can be specified by using the usual Spring conventions, as shown in the following example: file:/home/user/test.dat .

46.3.5 Web Application Conditions

The @ConditionalOnWebApplication and @ConditionalOnNotWebApplication annotations let configuration be included depending on whether the application is a 'web application'. A web application is any application that is using a Spring WebApplicationContext , defines a session scope, or has a StandardServletEnvironment .

46.3.6 SpEL Expression Conditions

The @ConditionalOnExpression annotation lets configuration be included based on the result of a SpEL expression .

46.4 Creating Your Own Starter

A full Spring Boot starter for a library may contain the following components:

The autoconfigure module that contains the auto-configuration code.
The starter module that provides a dependency to the autoconfigure module as well as the library and any additional dependencies that are typically useful. In a nutshell, adding the starter should provide everything needed to start using that library.

	Tip
	You may combine the auto-configuration code and the dependency management in a single module if you do not need to separate those two concerns.

46.4.1 Naming

You should make sure to provide a proper namespace for your starter. Do not start your module names with spring-boot , even if you are using a different Maven groupId . We may offer official support for the thing you auto-configure in the future.

As a rule of thumb, you should name a combined module after the starter. For example, assume that you are creating a starter for "acme" and that you name the auto-configure module acme-spring-boot-autoconfigure and the starter acme-spring-boot-starter . If you only have one module that combines the two, name it acme-spring-boot-starter .

Also, if your starter provides configuration keys, use a proper (that is, unique) namespace for them. In particular, do not include your keys in the namespaces that Spring Boot uses (such as server , management , spring , and so on). If you use the same namespace, we may modify these namespaces in the future in ways that break your modules.

Make sure to trigger meta-data generation so that IDE assistance is available for your keys as well. You may want to review the generated meta-data ( META-INF/spring-configuration-metadata.json ) to make sure your keys are properly documented.

46.4.2 `autoconfigure` Module

The autoconfigure module contains everything that is necessary to get started with the library. It may also contain configuration key definitions (such as @ConfigurationProperties ) and any callback interface that can be used to further customize how the components are initialized.

	Tip
	You should mark the dependencies to the library as optional so that you can include the `autoconfigure` module in your projects more easily. If you do it that way, the library is not provided and, by default, Spring Boot backs off.

46.4.3 Starter Module

The starter is really an empty jar. Its only purpose is to provide the necessary dependencies to work with the library. You can think of it as an opinionated view of what is required to get started.

Do not make assumptions about the project in which your starter is added. If the library you are auto-configuring typically requires other starters, mention them as well. Providing a proper set of default dependencies may be hard if the number of optional dependencies is high, as you should avoid including dependencies that are unnecessary for a typical usage of the library. In other words, you should not include optional dependencies.

47. What to Read Next

If you want to learn more about any of the classes discussed in this section, you can check out the Spring Boot API documentation or you can browse the source code directly . If you have specific questions, take a look at the how-to section.

If you are comfortable with Spring Boot’s core features, you can continue on and read about production-ready features .

Part V. Spring Boot Actuator: Production-ready features

Spring Boot includes a number of additional features to help you monitor and manage your application when you push it to production. You can choose to manage and monitor your application by using HTTP endpoints or with JMX. Auditing, health, and metrics gathering can also be automatically applied to your application.

48. Enabling Production-ready Features

The spring-boot-actuator module provides all of Spring Boot’s production-ready features. The simplest way to enable the features is to add a dependency to the spring-boot-starter-actuator ‘Starter’.

To add the actuator to a Maven based project, add the following ‘Starter’ dependency:

<dependencies>
	<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-actuator</artifactId>
	</dependency>
</dependencies>

For Gradle, use the following declaration:

dependencies {
	compile("org.springframework.boot:spring-boot-starter-actuator")
}

49. Endpoints

Actuator endpoints let you monitor and interact with your application. Spring Boot includes a number of built-in endpoints and lets you add your own. For example, the health endpoint provides basic application health information.

The way that endpoints are exposed depends on the type of technology that you choose. Most applications choose HTTP monitoring, where the ID of the endpoint along with a prefix of /actuator is mapped to a URL. For example, by default, the health endpoint is mapped to /actuator/health .

The following technology-agnostic endpoints are available:

ID	Description
`auditevents`	Exposes audit events information for the current application.
`conditions`	Showing the conditions that were evaluated on configuration and auto-configuration classes and the reasons why they did or did not match.
`beans`	Displays a complete list of all the Spring beans in your application.
`configprops`	Displays a collated list of all `@ConfigurationProperties` .
`env`	Exposes properties from Spring’s `ConfigurableEnvironment` .
`flyway`	Shows any Flyway database migrations that have been applied.
`health`	Shows application health information.
`info`	Displays arbitrary application info.
`loggers`	Shows and modifies the configuration of loggers in the application.
`liquibase`	Shows any Liquibase database migrations that have been applied.
`metrics`	Shows ‘metrics’ information for the current application.
`mappings`	Displays a collated list of all `@RequestMapping` paths.
`scheduledtasks`	Displays the scheduled tasks in your application.
`sessions`	Allows retrieval and deletion of user sessions from a Spring Session-backed session store. Not available when using Spring Session’s support for reactive web applications.
`shutdown`	Lets the application be gracefully shutdown (not enabled by default).
`threaddump`	Performs a thread dump.
`trace`	Displays trace information (by default, the last 100 HTTP requests).

If your application is a web application (Spring MVC, Spring WebFlux, or Jersey), you can use the following additional endpoints:

ID	Description
`heapdump`	Returns a GZip compressed `hprof` heap dump file.
`logfile`	Returns the contents of the logfile (if `logging.file` or `logging.path` properties have been set). Supports the use of the HTTP `Range` header to retrieve part of the log file’s content.
`prometheus`	Exposes metrics in a format that can be scraped by a Prometheus server.

To learn more about the Actuator’s endpoints and their request and response formats, please refer to the separate API documentation that is available in the following formats:

HTML
PDF

49.1 Exposing Endpoints

Since Endpoints may contain sensitive information, careful consideration should be given about when to expose them. Out of the box, Spring Boot will expose all enabled endpoints over JMX, but only the health and info endpoints over HTTP.

To change the endpoints that are exposed you can use the expose and exclude property for the technology. For example, to only expose the health over JMX you would use:

application.properties.

management.endpoints.jmx.expose=health

The * character can be used to indicate all endpoints. For example, to expose everything over HTTP except the env endpoint you would use:

application.properties.

management.endpoints.web.expose=*
management.endpoints.web.exclude=env

	Note
	If your application is exposed publicly we strongly recommend that you also secure your endpoints .

	Tip
	If you want to implement your own strategy for when endpoints are exposed you can register an `EndpointFilter` bean.

49.2 Securing HTTP Endpoints

You should take care to secure HTTP endpoints in the same way that you would any other sensitive URL. Spring Boot will not apply any security on your behalf, however, it does provide some convenient RequestMatcher s that can be used in combination with Spring Security.

A typical Spring Security configuration could look something like this:

@Configuration
public class ActuatorSecurity extends WebSecurityConfigurerAdapter {
	@Override
	protected void configure(HttpSecurity http) throws Exception {
		http.requestMatcher(EndpointRequest.toAnyEndpoint()).authorizeRequests()
				.anyRequest().hasRole("ENDPOINT_ADMIN")
				.and()
			.httpBasic();
}

The above uses EndpointRequest.toAnyEndpoint() to match a request to any endpoint, then ensure that all have the ENDPOINT_ADMIN role. Several other matcher methods are also available on EndpointRequest (see the API documentation for details).

If you deploy applications behind a firewall, you may prefer that all your actuator endpoints can be accessed without requiring authentication. You can do so by changing the management.endpoints.web.expose property, as follows:

application.properties.

management.endpoints.web.expose=*

49.3 Customizing Endpoints

Endpoints can be customized by using Spring properties. You can change whether an endpoint is enabled and the amount of time it will cache responses.

For example, the following application.properties changes the time-to-live of the beans endpoint to 10 seconds and also enables shutdown :

management.endpoint.beans.cache.time-to-live=10s
management.endpoint.shutdown.enabled=true

	Note
	The prefix `management.endpoint.<name>` is used to uniquely identify the endpoint that is being configured.

By default, all endpoints except for shutdown are enabled. If you prefer to specifically “opt-in” endpoint enablement, you can use the management.endpoints.enabled-by-default property. For example, the following settings disable all endpoints except for info :

management.endpoints.enabled-by-default=false
management.endpoint.info.enabled=true

	Note
	Disabled endpoints are removed entirely from the `ApplicationContext` . If you only want to change the technologies over which an endpoint is exposed you can use the `expose` and `exclude` properties (see Section 49.1, “Exposing Endpoints” ).

49.4 Hypermedia for Actuator Web Endpoints

A “discovery page” is added with links to all the endpoints. The “discovery page” is available on /actuator by default.

When a custom management context path is configured, the “discovery page” automatically moves from /actuator to the root of the management context. For example, if the management context path is /management , then the discovery page is available from /management . When the management context path is set to / , the discovery page is disabled to prevent the possibility of a clash with other mappings.

49.5 Actuator Web Endpoint Paths

By default, endpoints are exposed over HTTP under the /actuator path using ID of the endpoint. For example, the beans endpoint is exposed under /actuator/beans . If you want to map endpoints to a different path you can use the management.endpoints.web.path-mapping property. You can also use management.endpoints.web.base-path if you want change the base path.

Here’s an example that remaps /actuator/health to /healthcheck :

application.properties.

management.endpoints.web.base-path=/
management.endpoints.path-mapping.health=healthcheck

49.6 CORS Support

Cross-origin resource sharing (CORS) is a W3C specification that allows you to specify in a flexible way what kind of cross domain requests are authorized. If you use Spring MVC or Spring WebFlux, Actuator’s web endpoints can be configured to support such scenarios.

CORS support is disabled by default and is only enabled once the management.endpoints.web.cors.allowed-origins property has been set. The following configuration permits GET and POST calls from the example.com domain:

management.endpoints.web.cors.allowed-origins=http://example.com
management.endpoints.web.cors.allowed-methods=GET,POST

	Tip
	See CorsEndpointProperties for a complete list of options.

49.7 Adding Custom Endpoints

If you add a @Bean annotated with @Endpoint , any methods annotated with @ReadOperation , @WriteOperation or @DeleteOperation are automatically exposed over JMX and, in a web application, over HTTP as well.

You can also write technology specific endpoints by using @JmxEndpoint or @WebEndpoint . These endpoints are filtered to their respective technologies. For example, @WebEndpoint will be exposed only over HTTP and not over JMX.

Finally, it’s possible to write technology specific extensions using @EndpointWebExtension and @EndpointJmxExtension . These annotations allow you to provide technology specific operations to augment an existing endpoint.

Tip

If you add endpoints as a library feature, consider adding a configuration class annotated with @ManagementContextConfiguration to /META-INF/spring.factories under the key, org.springframework.boot.actuate.autoconfigure.ManagementContextConfiguration . If you do so and if your users ask for a separate management port or address, the endpoint moves to a child context with all the other web endpoints.

49.8 Health Information

You can use health information to check the status of your running application. It is often used by monitoring software to alert someone when a production system goes down. The information exposed by the health endpoint depends on the management.endpoint.health.show-details property. By default, the property’s value is false and a simple ‘status’ message is returned. When the property’s value is set to true , additional details from the individual health indicators are also displayed.

Health information is collected from all HealthIndicator beans defined in your ApplicationContext . Spring Boot includes a number of auto-configured HealthIndicators , and you can also write your own. By default, the final system state is derived by the HealthAggregator , which sorts the statuses from each HealthIndicator based on an ordered list of statuses. The first status in the sorted list is used as the overall health status. If no HealthIndicator returns a status that is known to the HealthAggregator , an UNKNOWN status is used.

49.8.1 Auto-configured HealthIndicators

The following HealthIndicators are auto-configured by Spring Boot when appropriate:

Name	Description
`CassandraHealthIndicator`	Checks that a Cassandra database is up.
`DiskSpaceHealthIndicator`	Checks for low disk space.
`DataSourceHealthIndicator`	Checks that a connection to `DataSource` can be obtained.
`ElasticsearchHealthIndicator`	Checks that an Elasticsearch cluster is up.
`JmsHealthIndicator`	Checks that a JMS broker is up.
`MailHealthIndicator`	Checks that a mail server is up.
`MongoHealthIndicator`	Checks that a Mongo database is up.
`Neo4jHealthIndicator`	Checks that a Neo4j server is up.
`RabbitHealthIndicator`	Checks that a Rabbit server is up.
`RedisHealthIndicator`	Checks that a Redis server is up.
`SolrHealthIndicator`	Checks that a Solr server is up.

	Tip
	It is possible to disable them all using the `management.health.defaults.enabled` property.

49.8.2 Writing Custom HealthIndicators

To provide custom health information, you can register Spring beans that implement the HealthIndicator interface. You need to provide an implementation of the health() method and return a Health response. The Health response should include a status and can optionally include additional details to be displayed. The following code shows a sample HealthIndicator implementation:

import org.springframework.boot.actuate.health.Health;
import org.springframework.boot.actuate.health.HealthIndicator;
import org.springframework.stereotype.Component;
@Component
public class MyHealthIndicator implements HealthIndicator {
	@Override
	public Health health() {
		int errorCode = check(); // perform some specific health check
		if (errorCode != 0) {
			return Health.down().withDetail("Error Code", errorCode).build();
		return Health.up().build();
}

	Note
	The identifier for a given `HealthIndicator` is the name of the bean without the `HealthIndicator` suffix, if it exists. In the preceding example, the health information is available in an entry named `my` .

In addition to Spring Boot’s predefined Status types, it is also possible for Health to return a custom Status that represents a new system state. In such cases, a custom implementation of the HealthAggregator interface also needs to be provided, or the default implementation has to be configured by using the management.health.status.order configuration property.

For example, assume a new Status with code FATAL is being used in one of your HealthIndicator implementations. To configure the severity order, add the following to your application properties:

management.health.status.order=FATAL, DOWN, OUT_OF_SERVICE, UNKNOWN, UP

The HTTP status code in the response reflects the overall health status (for example, UP maps to 200, while OUT_OF_SERVICE and DOWN map to 503). You might also want to register custom status mappings if you access the health endpoint over HTTP. For example, the following property maps FATAL to 503 (service unavailable):

management.health.status.http-mapping.FATAL=503

	Tip
	If you need more control, you can define your own `HealthStatusHttpMapper` bean.

The following table shows the default status mappings for the built-in statuses:

Status	Mapping
DOWN	SERVICE_UNAVAILABLE (503)
OUT_OF_SERVICE	SERVICE_UNAVAILABLE (503)
UP	No mapping by default, so http status is 200
UNKNOWN	No mapping by default, so http status is 200

49.8.3 Reactive Health Indicators

For reactive applications, such as those using Spring WebFlux, ReactiveHealthIndicators provide a non-blocking contract for getting application health. Similar to a traditional HealthIndicator , health information is collected from all ReactiveHealthIndicator beans defined in your ApplicationContext . Regular HealthIndicators that do not check against a reactive API are included and executed on the elastic scheduler.

To provide custom health information from a reactive API, you can register Spring beans that implement the ReactiveHealthIndicator interface. The following code shows a sample ReactiveHealthIndicator implementation:

@Component
public class MyReactiveHealthIndicator implements ReactiveHealthIndicator {
	@Override
	public Mono<Health> health() {
		return doHealthCheck() //perform some specific health check that returns a Mono<Health>
			.onErrorResume(ex -> Mono.just(new Health.Builder().down(ex).build())));
}

	Tip
	To handle the error automatically, consider extending from `AbstractReactiveHealthIndicator` .

49.8.4 Auto-configured ReactiveHealthIndicators

The following ReactiveHealthIndicators are auto-configured by Spring Boot when appropriate:

Name	Description
`RedisReactiveHealthIndicator`	Checks that a Redis server is up.

	Tip
	Those reactive indicators replace the regular ones if necessary. Also, any `HealthIndicator` that is not handled explicitly is wrapped automatically.

49.9 Application Information

Application information exposes various information collected from all InfoContributor beans defined in your ApplicationContext . Spring Boot includes a number of auto-configured InfoContributors , and you can write your own.

49.9.1 Auto-configured InfoContributors

The following InfoContributors are auto-configured by Spring Boot, when appropriate:

Name	Description
`EnvironmentInfoContributor`	Expose any key from the `Environment` under the `info` key.
`GitInfoContributor`	Expose git information if a `git.properties` file is available.
`BuildInfoContributor`	Expose build information if a `META-INF/build-info.properties` file is available.

	Tip
	It is possible to disable them all using the `management.info.defaults.enabled` property.

49.9.2 Custom Application Information

You can customize the data exposed by the info endpoint by setting info.* Spring properties. All Environment properties under the info key are automatically exposed. For example, you could add the following settings to your application.properties file:

info.app.encoding=UTF-8
info.app.java.source=1.8
info.app.java.target=1.8

Tip

Rather than hardcoding those values, you could also expand info properties at build time .

Assuming you use Maven, you could rewrite the preceding example as follows:

info.app.encoding[email protected]@
info.app.java.source[email protected]@
info.app.java.target[email protected]@

49.9.3 Git Commit Information

Another useful feature of the info endpoint is its ability to publish information about the state of your git source code repository when the project was built. If a GitProperties bean is available, the git.branch , git.commit.id and git.commit.time properties are exposed.

	Tip
	A `GitProperties` bean is auto-configured if a `git.properties` file is available at the root of the classpath. See " Generate git information " for more details.

If you want to display the full git information (that is, the full content of git.properties ), use the management.info.git.mode property, as follows:

management.info.git.mode=full

49.9.4 Build Information

If a BuildProperties bean is available, the info endpoint can also publish information about your build. This happens if a META-INF/build-info.properties file is available in the classpath.

	Tip
	The Maven and Gradle plugins can both generate that file. See " Generate build information " for more details.

49.9.5 Writing Custom InfoContributors

To provide custom application information, you can register Spring beans that implement the InfoContributor interface.

The following example contributes an example entry with a single value:

import java.util.Collections;
import org.springframework.boot.actuate.info.Info;
import org.springframework.boot.actuate.info.InfoContributor;
import org.springframework.stereotype.Component;
@Component
public class ExampleInfoContributor implements InfoContributor {
	@Override
	public void contribute(Info.Builder builder) {
		builder.withDetail("example",
				Collections.singletonMap("key", "value"));
}

If you reach the info endpoint, you should see a response that contains the following additional entry:

{
	"example": {
		"key" : "value"
}

50. Monitoring and Management over HTTP

If you are developing a web application, Spring Boot Actuator auto-configures all enabled endpoints to be exposed over HTTP. The default convention is to use the id of the endpoint with a prefix of /actuator as the URL path. For example, health is exposed as /actuator/health .

	Tip
	Actuator is supported natively with Spring MVC, Spring WebFlux and Jersey.

50.1 Customizing the Management Endpoint Paths

Sometimes, it is useful to customize the prefix for the management endpoints. For example, your application might already use /actuator for another purpose. You can use the management.endpoints.web.base-path property to change the prefix for your management endpoint, as shown in the following example:

management.endpoints.web.base-path=/manage

The preceding application.properties example changes the endpoint from /actuator/{id} to /manage/{id} (e.g. /manage/info ).

	Note
	Unless the management port has been configured to expose endpoints using a different HTTP port , `management.endpoints.web.base-path` is relative to `server.context-path` . If `management.server.port` is configured, `management.endpoints.web.base-path` is relative to `management.server.servlet.context-path` .

50.2 Customizing the Management Server Port

Exposing management endpoints by using the default HTTP port is a sensible choice for cloud based deployments. If, however, your application runs inside your own data center, you may prefer to expose endpoints by using a different HTTP port.

You can set the management.server.port property to change the HTTP port, as shown in the following example:

management.server.port=8081

Since your management port is often protected by a firewall and not exposed to the public, you might not need security on the management endpoints, even if your main application is secure. In that case, you should have Spring Security on the classpath, and you can disable management security as follows:

management.security.enabled=false

(If you do not have Spring Security on the classpath, there is no need to explicitly disable the management security in this way. Doing so might even break the application.)

50.3 Configuring Management-specific SSL

When configured to use a custom port, the management server can also be configured with its own SSL by using the various management.server.ssl.* properties. For example, doing so lets a management server be available via HTTP while the main application uses HTTPS, as shown in the following property settings:

server.port=8443
server.ssl.enabled=true
server.ssl.key-store=classpath:store.jks
server.ssl.key-password=secret
management.server.port=8080
management.server.ssl.enabled=false

Alternatively, both the main server and the management server can use SSL but with different key stores, as follows:

server.port=8443
server.ssl.enabled=true
server.ssl.key-store=classpath:main.jks
server.ssl.key-password=secret
management.server.port=8080
management.server.ssl.enabled=true
management.server.ssl.key-store=classpath:management.jks
management.server.ssl.key-password=secret

50.4 Customizing the Management Server Address

You can customize the address that the management endpoints are available on by setting the management.server.address property. Doing so can be useful if you want to listen only on an internal or ops-facing network or to listen only for connections from localhost .

	Note
	You can only listen on a different address if the port is different from the main server port.

The following example application.properties does not allow remote management connections:

management.server.port=8081
management.server.address=127.0.0.1

50.5 Disabling HTTP Endpoints

If you do not want to expose endpoints over HTTP, you can set the management port to -1 , as shown in the following example:

management.server.port=-1

51. Monitoring and Management over JMX

Java Management Extensions (JMX) provide a standard mechanism to monitor and manage applications. By default, Spring Boot exposes management endpoints as JMX MBeans under the org.springframework.boot domain.

51.1 Customizing MBean Names

The name of the MBean is usually generated from the id of the endpoint. For example the health endpoint is exposed as org.springframework.boot:type=Endpoint,name=Health .

If your application contains more than one Spring ApplicationContext , you may find that names clash. To solve this problem, you can set the management.endpoints.jmx.unique-names property to true so that MBean names are always unique.

You can also customize the JMX domain under which endpoints are exposed. The following settings show an example of doing so in application.properties :

management.endpoints.jmx.domain=com.example.myapp
management.endpoints.jmx.unique-names=true

51.2 Disabling JMX Endpoints

If you do not want to expose endpoints over JMX, you can set the management.endpoints.jmx.enabled property to false , as shown in the following example:

management.endpoints.jmx.enabled=false

51.3 Using Jolokia for JMX over HTTP

Jolokia is a JMX-HTTP bridge that provides an alternative method of accessing JMX beans. To use Jolokia, include a dependency to org.jolokia:jolokia-core . For example, with Maven, you would add the following dependency:

<dependency>
	<groupId>org.jolokia</groupId>
	<artifactId>jolokia-core</artifactId>
	</dependency>

Jolokia can then be accessed by using /actuator/jolokia on your management HTTP server.

51.3.1 Customizing Jolokia

Jolokia has a number of settings that you would traditionally configure using servlet parameters. With Spring Boot, you can use your application.properties . Prefix the parameter with management.jolokia.config. , as shown in the following example:

management.jolokia.config.debug=true

51.3.2 Disabling Jolokia

If you use Jolokia but do not want Spring Boot to configure it, set the management.jolokia.enabled property to false , as follows:

management.jolokia.enabled=false

52. Loggers

Spring Boot Actuator includes the ability to view and configure the log levels of your application at runtime. You can view either the entire list or an individual logger’s configuration, which is made up of both the explicitly configured logging level as well as the effective logging level given to it by the logging framework. These levels can be one of:

TRACE
DEBUG
INFO
WARN
ERROR
FATAL
OFF
null

null indicates that there is no explicit configuration.

52.1 Configure a Logger

In order to configure a given logger, you POST a partial entity to the resource’s URI, as shown in the following example:

{
	"configuredLevel": "DEBUG"
}

	Tip
	To "reset" the specific level of the logger (and use the default configuration instead), you can pass a value of `null` as the `configuredLevel` .

53. Metrics

Spring Boot Actuator provides dependency management and auto-configuration for Micrometer , an application metrics facade that supports numerous monitoring systems:

Micrometer provides a separate module for each supported monitoring system. Depending on one (or more) of these modules is sufficient to get started with Micrometer in your Spring Boot application. To learn more about Micrometer’s capabilities, please refer to its reference documentation .

53.1 Spring MVC Metrics

Auto-configuration enables the instrumentation of requests handled by Spring MVC. When spring.metrics.web.server.auto-time-requests is true , this instrumentation occurs for all requests. Alternatively, when set to false , you can enable instrumentation by adding @Timed to a request-handling method.

By default, metrics are generated with the name, http.server.requests . The name can be customized by setting the spring.metrics.web.server.requests-metrics-name property.

53.1.1 Spring MVC Metric Tags

By default, Spring MVC-related metrics are tagged with the following information:

The request’s method.
The request’s URI (templated if possible).
The simple class name of any exception that was thrown while handling the request.
The response’s status.

To customize the tags, provide a @Bean that implements WebMvcTagsProvider .

53.2 WebFlux Metrics

Auto-configuration enables the instrumentation of all requests handled by WebFlux controllers. You can also use a helper class, RouterFunctionMetrics , to instrument applications that use WebFlux’s functional programming model.

By default, metrics are generated with the name http.server.requests . You can customize the name by setting the spring.metrics.web.server.requests-metrics-name property.

53.2.1 WebFlux Metric Tags

By default, WebFlux-related metrics for the annotation-based programming model are tagged with the following information:

The request’s method.
The request’s URI (templated if possible).
The simple class name of any exception that was thrown while handling the request.
The response’s status.

To customize the tags, provide a @Bean that implements WebFluxTagsProvider .

By default, metrics for the functional programming model are tagged with the following information:

The request’s method
The request’s URI (templated if possible).
The response’s status.

To customize the tags, use the defaultTags method on your RouterFunctionMetrics instance.

53.3 RestTemplate Metrics

Auto-configuration customizes the auto-configured RestTemplate to enable the instrumentation of its requests. MetricsRestTemplateCustomizer can be used to customize your own RestTemplate instances.

By default, metrics are generated with the name, http.client.requests . The name can be customized by setting the spring.metrics.web.client.requests-metrics-name property.

53.3.1 RestTemplate Metric Tags

By default, metrics generated by an instrumented RestTemplate are tagged with the following information:

The request’s method.
The request’s URI (templated if possible).
The response’s status.
The request URI’s host.

53.4 DataSource metrics

Auto-configuration will enable the instrumentation of all available DataSource s with a metric named data.source . Data source instrumentation results in gauges representing the currently active, maximum allowed, and minimum allowed connections in the pool. Each of these gauges has a name which is prefixed by data.source by default. The prefix can be customized by using the spring.metrics.jdbc.datasource-metric-name property.

Metrics will also be tagged by the name of the DataSource computed based on the bean name.

53.5 Spring Integration Metrics

Auto-configuration enables binding of a number of Spring Integration-related metrics:

Table 53.1. General metrics

Metric	Description
`spring.integration.channelNames`	Number of Spring Integration channels
`spring.integration.handlerNames`	Number of Spring Integration handlers
`spring.integration.sourceNames`	Number of Spring Integration sources

Table 53.2. Channel metrics

Metric	Description
`spring.integration.channel.receives`	Number of receives
`spring.integration.channel.sendErrors`	Number of failed sends
`spring.integration.channel.sends`	Number of successful sends

Table 53.3. Handler metrics

Metric	Description
`spring.integration.handler.duration.max`	Maximum handler duration in milliseconds
`spring.integration.handler.duration.min`	Minimum handler duration in milliseconds
`spring.integration.handler.duration.mean`	Mean handler duration in milliseconds
`spring.integration.handler.activeCount`	Number of active handlers

Table 53.4. Source metrics

Metric	Description
`spring.integration.source.messages`	Number of successful source calls

54. Auditing

Once Spring Security is in play Spring Boot Actuator has a flexible audit framework that publishes events (by default, ‘authentication success’, ‘failure’ and ‘access denied’ exceptions). This feature can be very useful for reporting and for implementing a lock-out policy based on authentication failures. To customize published security events, you can provide your own implementations of AbstractAuthenticationAuditListener and AbstractAuthorizationAuditListener .

You can also use the audit services for your own business events. To do so, either inject the existing AuditEventRepository into your own components and use that directly or publish an AuditApplicationEvent with the Spring ApplicationEventPublisher (by implementing ApplicationEventPublisherAware ).

55. Tracing

Tracing is automatically enabled for all HTTP requests. You can view the trace endpoint and obtain basic information about the last 100 requests. The following listing shows sample output:

[{
	"timestamp": 1394343677415,
	"info": {
		"method": "GET",
		"path": "/trace",
		"headers": {
			"request": {
				"Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
				"Connection": "keep-alive",
				"Accept-Encoding": "gzip, deflate",
				"User-Agent": "Mozilla/5.0 Gecko/Firefox",
				"Accept-Language": "en-US,en;q=0.5",
				"Cookie": "_ga=GA1.1.827067509.1390890128; ..."
				"Authorization": "Basic ...",
				"Host": "localhost:8080"
			"response": {
				"Strict-Transport-Security": "max-age=31536000 ; includeSubDomains",
				"X-Application-Context": "application:8080",
				"Content-Type": "application/json;charset=UTF-8",
				"status": "200"
	"timestamp": 1394343684465,
}]

By default, the trace includes the following information:

Name	Description
Request Headers	Headers from the request.
Response Headers	Headers from the response.
Cookies	`Cookie` from request headers and `Set-Cookie` from response headers.
Errors	The error attributes (if any).
Time Taken	The time taken to service the request in milliseconds.

55.1 Custom tracing

If you need to trace additional events, you can inject a TraceRepository into your Spring beans. The add method accepts a single Map structure that is converted to JSON and logged.

By default, an InMemoryTraceRepository that stores the last 100 events is used. If you need to expand the capacity, you can define your own instance of the InMemoryTraceRepository bean. You can also create your own alternative TraceRepository implementation.

56. Process Monitoring

In the spring-boot module, you can find two classes to create files that are often useful for process monitoring:

ApplicationPidFileWriter creates a file containing the application PID (by default, in the application directory with the file name, application.pid ).
EmbeddedServerPortFileWriter creates a file (or files) containing the ports of the embedded server (by default, in the application directory with the file name application.port ).

By default, these writers are not activated, but you can enable them in one of the ways described in the next section.

56.1 Extend Configuration

In the META-INF/spring.factories file, you can activate the listener(s) that writes a PID file, as shown in the following example:

org.springframework.context.ApplicationListener=\
org.springframework.boot.system.ApplicationPidFileWriter,\
org.springframework.boot.system.EmbeddedServerPortFileWriter

56.2 Programmatically

You can also activate a listener by invoking the SpringApplication.addListeners(…) method and passing the appropriate Writer object. This method also lets you customize the file name and path in the Writer constructor.

57. Cloud Foundry Support

Spring Boot’s actuator module includes additional support that is activated when you deploy to a compatible Cloud Foundry instance. The /cloudfoundryapplication path provides an alternative secured route to all @Endpoint beans.

The extended support lets Cloud Foundry management UIs (such as the web application that you can use to view deployed applications) be augmented with Spring Boot actuator information. For example, an application status page may include full health information instead of the typical “running” or “stopped” status.

	Note
	The `/cloudfoundryapplication` path is not directly accessible to regular users. In order to use the endpoint, a valid UAA token must be passed with the request.

57.1 Disabling Extended Cloud Foundry Actuator Support

If you want to fully disable the /cloudfoundryapplication endpoints, you can add the following setting to your application.properties file:

application.properties.

management.cloudfoundry.enabled=false

57.2 Cloud Foundry Self-signed Certificates

By default, the security verification for /cloudfoundryapplication endpoints makes SSL calls to various Cloud Foundry services. If your Cloud Foundry UAA or Cloud Controller services use self-signed certificates, you need to set the following property:

application.properties.

management.cloudfoundry.skip-ssl-validation=true

57.3 Custom Security Configuration

If you define custom security configuration and you want extended Cloud Foundry actuator support, you should ensure that /cloudfoundryapplication/** paths are open. Without a direct open route, your Cloud Foundry application manager is not able to obtain endpoint data.

For Spring Security, you typically include something like mvcMatchers("/cloudfoundryapplication/**").permitAll() in your configuration, as shown in the following example:

@Override
protected void configure(HttpSecurity http) throws Exception {
		.authorizeRequests()
			.mvcMatchers("/cloudfoundryapplication/**")
				.permitAll()
			.mvcMatchers("/mypath")
				.hasAnyRole("SUPERUSER")
			.anyRequest()
				.authenticated().and()
		.httpBasic();
}

58. What to Read Next

If you want to explore some of the concepts discussed in this chapter, you can take a look at the actuator sample applications . You also might want to read about graphing tools such as Graphite .

Otherwise, you can continue on, to read about ‘deployment options’ or jump ahead for some in-depth information about Spring Boot’s build tool plugins .

Part VI. Deploying Spring Boot Applications

Spring Boot’s flexible packaging options provide a great deal of choice when it comes to deploying your application. You can deploy Spring Boot applications to a variety of cloud platforms, to container images (such as Docker), or to virtual/real machines.

This section covers some of the more common deployment scenarios.

59. Deploying to the Cloud

Spring Boot’s executable jars are ready-made for most popular cloud PaaS (Platform-as-a-Service) providers. These providers tend to require that you “bring your own container”. They manage application processes (not Java applications specifically), so they need some intermediary layer that adapts your application to the cloud’s notion of a running process.

Ideally, your application, like a Spring Boot executable jar, has everything that it needs to run packaged within it.

In this section, we look at what it takes to get the simple application that we developed in the “Getting Started” section up and running in the Cloud.

59.1 Cloud Foundry

Cloud Foundry provides default buildpacks that come into play if no other buildpack is specified. The Cloud Foundry Java buildpack has excellent support for Spring applications, including Spring Boot. You can deploy stand-alone executable jar applications as well as traditional .war packaged applications.

Once you have built your application (by using, for example, mvn clean package ) and have installed the cf command line tool , deploy your application by using the cf push command, substituting the path to your compiled .jar . Be sure to have logged in with your cf command line client before pushing an application. The following line shows using the cf push command to deploy an application:

$ cf push acloudyspringtime -p target/demo-0.0.1-SNAPSHOT.jar

	Note
	In the preceding example, we substitute `acloudyspringtime` for whatever value you give `cf` as the name of your application.

See the cf push documentation for more options. If there is a Cloud Foundry manifest.yml file present in the same directory, it is considered.

At this point, cf starts uploading your application, producing output similar to the following example:

Uploading acloudyspringtime... OK
Preparing to start acloudyspringtime... OK
-----> Downloaded app package (8.9M)
-----> Java Buildpack Version: v3.12 (offline) | https://github.com/cloudfoundry/java-buildpack.git#6f25b7e
-----> Downloading Open Jdk JRE 1.8.0_121 from https://java-buildpack.cloudfoundry.org/openjdk/trusty/x86_64/openjdk-1.8.0_121.tar.gz (found in cache)
       Expanding Open Jdk JRE to .java-buildpack/open_jdk_jre (1.6s)
-----> Downloading Open JDK Like Memory Calculator 2.0.2_RELEASE from https://java-buildpack.cloudfoundry.org/memory-calculator/trusty/x86_64/memory-calculator-2.0.2_RELEASE.tar.gz (found in cache)
       Memory Settings: -Xss349K -Xmx681574K -XX:MaxMetaspaceSize=104857K -Xms681574K -XX:MetaspaceSize=104857K
-----> Downloading Container Certificate Trust Store 1.0.0_RELEASE from https://java-buildpack.cloudfoundry.org/container-certificate-trust-store/container-certificate-trust-store-1.0.0_RELEASE.jar (found in cache)
       Adding certificates to .java-buildpack/container_certificate_trust_store/truststore.jks (0.6s)
-----> Downloading Spring Auto Reconfiguration 1.10.0_RELEASE from https://java-buildpack.cloudfoundry.org/auto-reconfiguration/auto-reconfiguration-1.10.0_RELEASE.jar (found in cache)
Checking status of app 'acloudyspringtime'...
  0 of 1 instances running (1 starting)
  0 of 1 instances running (1 starting)
  0 of 1 instances running (1 starting)
  1 of 1 instances running (1 running)
App started

Congratulations! The application is now live!

Once your application is live, you can verify the status of the deployed application by using the cf apps command, as shown in the following example:

$ cf apps
Getting applications in ...
name                 requested state   instances   memory   disk   urls
acloudyspringtime    started           1/1         512M     1G     acloudyspringtime.cfapps.io
...

Once Cloud Foundry acknowledges that your application has been deployed, you should be able to find the application at the URI given. In the preceding example, you could find it at http://acloudyspringtime.cfapps.io/ .

59.1.1 Binding to Services

By default, metadata about the running application as well as service connection information is exposed to the application as environment variables (for example: $VCAP_SERVICES ). This architecture decision is due to Cloud Foundry’s polyglot (any language and platform can be supported as a buildpack) nature. Process-scoped environment variables are language agnostic.

Environment variables do not always make for the easiest API, so Spring Boot automatically extracts them and flattens the data into properties that can be accessed through Spring’s Environment abstraction, as shown in the following example:

@Component
class MyBean implements EnvironmentAware {
	private String instanceId;
	@Override
	public void setEnvironment(Environment environment) {
		this.instanceId = environment.getProperty("vcap.application.instance_id");
	// ...
}

All Cloud Foundry properties are prefixed with vcap . You can use vcap properties to access application information (such as the public URL of the application) and service information (such as database credentials). See ‘CloudFoundryVcapEnvironmentPostProcessor’ Javadoc for complete details.

	Tip
	The Spring Cloud Connectors project is a better fit for tasks such as configuring a DataSource. Spring Boot includes auto-configuration support and a `spring-boot-starter-cloud-connectors` starter.

59.2 Heroku

Heroku is another popular PaaS platform. To customize Heroku builds, you provide a Procfile , which provides the incantation required to deploy an application. Heroku assigns a port for the Java application to use and then ensures that routing to the external URI works.

You must configure your application to listen on the correct port. The following example shows the Procfile for our starter REST application:

web: java -Dserver.port=$PORT -jar target/demo-0.0.1-SNAPSHOT.jar

Spring Boot makes -D arguments available as properties accessible from a Spring Environment instance. The server.port configuration property is fed to the embedded Tomcat, Jetty, or Undertow instance which, then uses the port when it starts up. The $PORT environment variable is assigned to us by the Heroku PaaS.

This should be everything you need. The most common deployment workflow for Heroku deployments is to git push the code to production, as shown in the following example:

$ git push heroku master
Initializing repository, done.
Counting objects: 95, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (78/78), done.
Writing objects: 100% (95/95), 8.66 MiB | 606.00 KiB/s, done.
Total 95 (delta 31), reused 0 (delta 0)
-----> Java app detected
-----> Installing OpenJDK 1.8... done
-----> Installing Maven 3.3.1... done
-----> Installing settings.xml... done
-----> Executing: mvn -B -DskipTests=true clean install
       [INFO] Scanning for projects...
       Downloading: http://repo.spring.io/...
       Downloaded: http://repo.spring.io/... (818 B at 1.8 KB/sec)
       Downloaded: http://s3pository.heroku.com/jvm/... (152 KB at 595.3 KB/sec)
       [INFO] Installing /tmp/build_0c35a5d2-a067-4abc-a232-14b1fb7a8229/target/...
       [INFO] Installing /tmp/build_0c35a5d2-a067-4abc-a232-14b1fb7a8229/pom.xml ...
       [INFO] ------------------------------------------------------------------------
       [INFO] BUILD SUCCESS
       [INFO] ------------------------------------------------------------------------
       [INFO] Total time: 59.358s
       [INFO] Finished at: Fri Mar 07 07:28:25 UTC 2014
       [INFO] Final Memory: 20M/493M
       [INFO] ------------------------------------------------------------------------
-----> Discovering process types
       Procfile declares types -> web
-----> Compressing... done, 70.4MB
-----> Launching... done, v6
       http://agile-sierra-1405.herokuapp.com/ deployed to Heroku
To [email protected]:agile-sierra-1405.git
 * [new branch]      master -> master

Your application should now be up and running on Heroku.

59.3 OpenShift

OpenShift is the Red Hat public (and enterprise) extension of the Kubernetes container orchestration platform. Similarly to Kubernetes, OpenShift has many options for installing Spring Boot based applications.

OpenShift has many resources describing how to deploy Spring Boot applications, which include:

59.4 Amazon Web Services (AWS)

Amazon Web Services offers multiple ways to install Spring Boot-based applications, either as traditional web applications (war) or as executable jar files with an embedded web server. The options include:

AWS Elastic Beanstalk
AWS Code Deploy
AWS OPS Works
AWS Cloud Formation
AWS Container Registry

Each has different features and pricing model. In this document, we describe only the simplest option: AWS Elastic Beanstalk.

59.4.1 AWS Elastic Beanstalk

As described in the official Elastic Beanstalk Java guide , there are two main options to deploy a Java application. You can either use the “Tomcat Platform” or the “Java SE platform”.

Using the Tomcat Platform

This option applies to Spring Boot projects that produce a war file. There is no any special configuration required. You need only follow the official guide.

Using the Java SE Platform

This option applies to Spring Boot projects that produce a jar file and run an embedded web container. Elastic Beanstalk environments run an nginx instance on port 80 to proxy the actual application, running on port 5000. To configure it, add the following line to your application.properties file:

server.port=5000

Upload binaries instead of sources

By default, Elastic Beanstalk uploads sources and compiles them in AWS. However, it is best to upload the binaries instead. To do so, add the following lines to your .elasticbeanstalk/config.yml file:

deploy:
	artifact: target/demo-0.0.1-SNAPSHOT.jar

Reduce costs by setting the environment type

By default an Elastic Beanstalk environment is load balanced. The load balancer has a significant cost. To avoid that cost, set the environment type to “Single instance”, as described in Amazon documentation. You can also create single instance environments by using the CLI and the following command:

eb create -s

59.4.2 Summary

This is one of the easiest ways to get to AWS, but there are more things to cover, such as how to integrate Elastic Beanstalk into any CI / CD tool, use the Elastic Beanstalk Maven plugin instead of the CLI, and others. There is a exampledriven.wordpress.com/2017/01/09/spring-boot-aws-elastic-beanstalk-example/ [blog post] covering these topics more in detail.

59.5 Boxfuse and Amazon Web Services

Boxfuse works by turning your Spring Boot executable jar or war into a minimal VM image that can be deployed unchanged either on VirtualBox or on AWS. Boxfuse comes with deep integration for Spring Boot and uses the information from your Spring Boot configuration file to automatically configure ports and health check URLs. Boxfuse leverages this information both for the images it produces as well as for all the resources it provisions (instances, security groups, elastic load balancers, and so on).

Once you have created a Boxfuse account , connected it to your AWS account, installed the latest version of the Boxfuse Client, and ensured that the application has been built by Maven or Gradle (by using, for example, mvn clean package ), you can deploy your Spring Boot application to AWS with a command similar to the following:

$ boxfuse run myapp-1.0.jar -env=prod

See the boxfuse run documentation for more options. If there is a boxfuse.com/docs/commandline/#configuration [ boxfuse.conf ] file present in the current directory, it is considered.

	Tip
	By default, Boxfuse activates a Spring profile named `boxfuse` on startup. If your executable jar or war contains an boxfuse.com/docs/payloads/springboot.html#configuration [ `application-boxfuse.properties` ] file, Boxfuse bases its configuration based on the properties it contains.

At this point, boxfuse creates an image for your application, uploads it, and configures and starts the necessary resources on AWS resulting in output similar to the following example:

Fusing Image for myapp-1.0.jar ...
Image fused in 00:06.838s (53937 K) -> axelfontaine/myapp:1.0
Creating axelfontaine/myapp ...
Pushing axelfontaine/myapp:1.0 ...
Verifying axelfontaine/myapp:1.0 ...
Creating Elastic IP ...
Mapping myapp-axelfontaine.boxfuse.io to 52.28.233.167 ...
Waiting for AWS to create an AMI for axelfontaine/myapp:1.0 in eu-central-1 (this may take up to 50 seconds) ...
AMI created in 00:23.557s -> ami-d23f38cf
Creating security group boxfuse-sg_axelfontaine/myapp:1.0 ...
Launching t2.micro instance of axelfontaine/myapp:1.0 (ami-d23f38cf) in eu-central-1 ...
Instance launched in 00:30.306s -> i-92ef9f53
Waiting for AWS to boot Instance i-92ef9f53 and Payload to start at http://52.28.235.61/ ...
Payload started in 00:29.266s -> http://52.28.235.61/
Remapping Elastic IP 52.28.233.167 to i-92ef9f53 ...
Waiting 15s for AWS to complete Elastic IP Zero Downtime transition ...
Deployment completed successfully. axelfontaine/myapp:1.0 is up and running at http://myapp-axelfontaine.boxfuse.io/

Your application should now be up and running on AWS.

See the blog post on deploying Spring Boot apps on EC2 as well as the documentation for the Boxfuse Spring Boot integration to get started with a Maven build to run the app.

59.6 Google Cloud

Google Cloud has several options that can be used to launch Spring Boot applications. The easiest to get started with is probably App Engine, but you could also find ways to run Spring Boot in a container with Container Engine or on a virtual machine with Compute Engine.

To run in App Engine, you can create a project in the UI first, which sets up a unique identifier for you and also sets up HTTP routes. Add a Java app to the project and leave it empty and then use the Google Cloud SDK to push your Spring Boot app into that slot from the command line or CI build.

App Engine needs you to create an app.yaml file to describe the resources your app requires. Normally you put this file in src/main/appengine , and it should resemble the following file:

service: default
runtime: java
env: flex
runtime_config:
  jdk: openjdk8
handlers:
- url: /.*
  script: this field is required, but ignored
manual_scaling:
  instances: 1
health_check:
  enable_health_check: False
env_variables:
  ENCRYPT_KEY: your_encryption_key_here

You can deploy the app (for example, with a Maven plugin) by adding the project ID to the build configuration, as shown in the following example:

<plugin>
	<groupId>com.google.cloud.tools</groupId>
	<artifactId>appengine-maven-plugin</artifactId>
	<version>1.3.0</version>
	<configuration>
		<project>myproject</project>
	</configuration>
</plugin>

Then deploy with mvn appengine:deploy (if you need to authenticate first, the build fails).

	Note
	Google App Engine Classic is tied to the Servlet 2.5 API, so you cannot deploy a Spring Application there without some modifications. See the Servlet 2.5 section of this guide.

60. Installing Spring Boot Applications

In additional to running Spring Boot applications by using java -jar , it is also possible to make fully executable applications for Unix systems. A fully executable jar can be executed like any other executable binary or it can be registered with init.d or systemd . This makes it very easy to install and manage Spring Boot applications in common production environments.

Warning

Fully executable jars work by embedding an extra script at the front of the file. Currently, some tools do not accept this format, so you may not always be able to use this technique. For example, jar -xf may silently fail to extract a jar or war that has been made fully executable. It is recommended that you only make your jar or war fully executable if you intend to execute it directly, rather than running it with java -jar or deploying it to a servlet container.

To create a ‘fully executable’ jar with Maven, use the following plugin configuration:

<plugin>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-maven-plugin</artifactId>
	<configuration>
		<executable>true</executable>
	</configuration>
</plugin>

The following example shows the equivalent Gradle configuration:

bootJar {
	launchScript()
}

You can then run your application by typing ./my-application.jar (where my-application is the name of your artifact). The directory containing the jar is used as your application’s working directory.

60.1 Supported Operating Systems

The default script supports most Linux distributions and is tested on CentOS and Ubuntu. Other platforms, such as OS X and FreeBSD, require the use of a custom embeddedLaunchScript .

60.2 Unix/Linux Services

Spring Boot application can be easily started as Unix/Linux services by using either init.d or systemd .

60.2.1 Installation as an `init.d` Service (System V)

If you configured Spring Boot’s Maven or Gradle plugin to generate a fully executable jar , and you do not use a custom embeddedLaunchScript , your application can be used as an init.d service. To do so, symlink the jar to init.d to support the standard start , stop , restart and status commands.

The script supports the following features:

Starts the services as the user that owns the jar file
Tracks the application’s PID by using /var/run/<appname>/<appname>.pid
Writes console logs to /var/log/<appname>.log

Assuming that you have a Spring Boot application installed in /var/myapp , to install a Spring Boot application as an init.d service, create a symlink, as follows:

$ sudo ln -s /var/myapp/myapp.jar /etc/init.d/myapp

Once installed, you can start and stop the service in the usual way. For example, on a Debian based system, you could start it with the following command:

$ service myapp start

	Tip
	If your application fails to start, check the log file written to `/var/log/<appname>.log` for errors.

You can also flag the application to start automatically by using your standard operating system tools. For example, on Debian, you could use the following command:

$ update-rc.d myapp defaults <priority>

Securing an `init.d` Service

	Note
	The following is a set of guidelines on how to secure a Spring Boot application that runs as an init.d service. It is not intended to be an exhaustive list of everything that should be done to harden an application and the environment in which it runs.

When executed as root, as is the case when root is being used to start an init.d service, the default executable script runs the application as the user who owns the jar file. You should never run a Spring Boot application as root , so your application’s jar file should never be owned by root. Instead, create a specific user to run your application and use chown to make it the owner of the jar file, as shown in the following example:

$ chown bootapp:bootapp your-app.jar

In this case, the default executable script runs the application as the bootapp user.

	Tip
	To reduce the chances of the application’s user account being compromised, you should consider preventing it from using a login shell. For example, you can set the account’s shell to `/usr/sbin/nologin` .

You should also take steps to prevent the modification of your application’s jar file. Firstly, configure its permissions so that it cannot be written and can only be read or executed by its owner, as shown in the following example:

$ chmod 500 your-app.jar

Second, you should also take steps to limit the damage if your application or the account that’s running it is compromised. If an attacker does gain access, they could make the jar file writable and change its contents. One way to protect against this is to make it immutable by using chattr , as shown in the following example:

$ sudo chattr +i your-app.jar

This will prevent any user, including root, from modifying the jar.

If root is used to control the application’s service and you use a .conf file to customize its startup, the .conf file is read and evaluated by the root user. It should be secured accordingly. Use chmod so that the file can only be read by the owner and use chown to make root the owner, as shown in the following example:

$ chmod 400 your-app.conf
$ sudo chown root:root your-app.conf

60.2.2 Installation as a `systemd` Service

systemd is the successor of the System V init system and is now being used by many modern Linux distributions. Although you can continue to use init.d scripts with systemd , it is also possible to launch Spring Boot applications by using systemd ‘service’ scripts.

Assuming that you have a Spring Boot application installed in /var/myapp , to install a Spring Boot application as a systemd service, create a script named myapp.service and place it in /etc/systemd/system directory. The following script offers an example:

[Unit]
Description=myapp
After=syslog.target
[Service]
User=myapp
ExecStart=/var/myapp/myapp.jar
SuccessExitStatus=143
[Install]
WantedBy=multi-user.target

	Important
	Remember to change the `Description` , `User` and `ExecStart` fields for your application.

	Note
	The `ExecStart` field does not declare the script action command, which means that the `run` command is used by default.

Note that, unlike when running as an init.d service, the user that runs the application, the PID file, and the console log file are managed by systemd itself and therefore must be configured by using appropriate fields in the ‘service’ script. Consult the service unit configuration man page for more details.

To flag the application to start automatically on system boot, use the following command:

$ systemctl enable myapp.service

Refer to man systemctl for more details.

60.2.3 Customizing the Startup Script

The default embedded startup script written by the Maven or Gradle plugin can be customized in a number of ways. For most people, using the default script along with a few customizations is usually enough. If you find you cannot customize something that you need to, you can always use the embeddedLaunchScript option to write your own file entirely.

Customizing the Start Script when It Is Written

It often makes sense to customize elements of the start script as it is written into the jar file. For example, init.d scripts can provide a “description”. Since you know the description up front (and it need not change), you may as well provide it when the jar is generated.

To customize written elements, use the embeddedLaunchScriptProperties option of the Spring Boot Maven or Gradle plugins.

The following property substitutions are supported with the default script:

Name	Description
`mode`	The script mode. Defaults to `auto` .
`initInfoProvides`	The `Provides` section of “INIT INFO”. Defaults to `spring-boot-application` for Gradle and to `${project.artifactId}` for Maven.
`initInfoRequiredStart`	The `Required-Start` section of “INIT INFO”. Defaults to `$remote_fs $syslog $network` .
`initInfoRequiredStop`	The `Required-Stop` section of “INIT INFO”. Defaults to `$remote_fs $syslog $network` .
`initInfoDefaultStart`	The `Default-Start` section of “INIT INFO”. Defaults to `2 3 4 5` .
`initInfoDefaultStop`	The `Default-Stop` section of “INIT INFO”. Defaults to `0 1 6` .
`initInfoShortDescription`	The `Short-Description` section of “INIT INFO”. Defaults to `Spring Boot Application` for Gradle and to `${project.name}` for Maven.
`initInfoDescription`	The `Description` section of “INIT INFO”. Defaults to `Spring Boot Application` for Gradle and to `${project.description}` (falling back to `${project.name}` ) for Maven.
`initInfoChkconfig`	The `chkconfig` section of “INIT INFO”. Defaults to `2345 99 01` .
`confFolder`	The default value for `CONF_FOLDER` . Defaults to the folder containing the jar.
`inlinedConfScript`	Reference to a file script that should be inlined in the default launch script. This can be used to set environmental variables such as `JAVA_OPTS` before any external config files are loaded.
`logFolder`	The default value for `LOG_FOLDER` . Only valid for an `init.d` service.
`logFilename`	The default value for `LOG_FILENAME` . Only valid for an `init.d` service.
`pidFolder`	The default value for `PID_FOLDER` . Only valid for an `init.d` service.
`pidFilename`	The default value for the name of the PID file in `PID_FOLDER` . Only valid for an `init.d` service.
`useStartStopDaemon`	Whether the `start-stop-daemon` command, when it’s available, should be used to control the process. Defaults to `true` .
`stopWaitTime`	The default value for `STOP_WAIT_TIME` . Only valid for an `init.d` service. Defaults to 60 seconds.

Customizing a Script When It Runs

For items of the script that need to be customized after the jar has been written, you can use environment variables or a config file .

The following environment properties are supported with the default script:

Variable	Description
`MODE`	The “mode” of operation. The default depends on the way the jar was built but is usually `auto` (meaning it tries to guess if it is an init script by checking if it is a symlink in a directory called `init.d` ). You can explicitly set it to `service` so that the `stop\|start\|status\|restart` commands work or to `run` if you want to run the script in the foreground.
`USE_START_STOP_DAEMON`	Whether the `start-stop-daemon` command, when it’s available, should be used to control the process. Defaults to `true` .
`PID_FOLDER`	The root name of the pid folder ( `/var/run` by default).
`LOG_FOLDER`	The name of the folder in which to put log files ( `/var/log` by default).
`CONF_FOLDER`	The name of the folder from which to read .conf files (same folder as jar-file by default).
`LOG_FILENAME`	The name of the log file in the `LOG_FOLDER` ( `<appname>.log` by default).
`APP_NAME`	The name of the app. If the jar is run from a symlink, the script guesses the app name if it is not a symlink or you want to explicitly set the app name, this can be useful.
`RUN_ARGS`	The arguments to pass to the program (the Spring Boot app).
`JAVA_HOME`	The location of the `java` executable is discovered by using the `PATH` by default, but you can set it explicitly if there is an executable file at `$JAVA_HOME/bin/java` .
`JAVA_OPTS`	Options that are passed to the JVM when it is launched.
`JARFILE`	The explicit location of the jar file, in case the script is being used to launch a jar that it is not actually embedded.
`DEBUG`	If not empty, sets the `-x` flag on the shell process, making it easy to see the logic in the script.
`STOP_WAIT_TIME`	The time in seconds to wait when stopping the application before forcing a shutdown ( `60` by default).

	Note
	The `PID_FOLDER` , `LOG_FOLDER` , and `LOG_FILENAME` variables are only valid for an `init.d` service. For `systemd` , the equivalent customizations are made by using the ‘service’ script. See the service unit configuration man page for more details.

With the exception of JARFILE and APP_NAME , the above settings can be configured by using a .conf file. The file is expected to be next to the jar file and have the same name but suffixed with .conf rather than .jar . For example, a jar named /var/myapp/myapp.jar uses the configuration file named /var/myapp/myapp.conf .

myapp.conf.

JAVA_OPTS=-Xmx1024M
LOG_FOLDER=/custom/log/folder

	Tip
	If you do not like having the config file next to the jar file, you can set a `CONF_FOLDER` environment variable to customize the location of the config file.

To learn about securing this file appropriately, see the guidelines for securing an init.d service .

60.3 Microsoft Windows Services

A Spring Boot application can be started as a Windows service by using winsw .

A sample ( maintained separately ) describes step-by-step how you can create a Windows service for your Spring Boot application.

61. What to Read Next

Check out the Cloud Foundry , Heroku , OpenShift , and Boxfuse web sites for more information about the kinds of features that a PaaS can offer. These are just four of the most popular Java PaaS providers. Since Spring Boot is so amenable to cloud-based deployment, you can freely consider other providers as well.

The next section goes on to cover the Spring Boot CLI , or you can jump ahead to read about build tool plugins .

Part VII. Spring Boot CLI

The Spring Boot CLI is a command line tool that you can use if you want to quickly develop a Spring application. It lets you run Groovy scripts, which means that you have a familiar Java-like syntax without so much boilerplate code. You can also bootstrap a new project or write your own command for it.

62. Installing the CLI

The Spring Boot CLI (Command-Line Interface) can be installed manually by using SDKMAN! (the SDK Manager) or by using Homebrew or MacPorts if you are an OSX user. See Section 10.2, “Installing the Spring Boot CLI” in the “Getting started” section for comprehensive installation instructions.

63. Using the CLI

Once you have installed the CLI, you can run it by typing spring and pressing Enter at the command line. If you run spring without any arguments, a simple help screen is displayed, as follows:

$ spring
usage: spring [--help] [--version]
       <command> [<args>]
Available commands are:
  run [options] <files> [--] [args]
    Run a spring groovy script
  ... more command help is shown here

You can type spring help to get more details about any of the supported commands, as shown in the following example:

$ spring help run
spring run - Run a spring groovy script
usage: spring run [options] <files> [--] [args]
Option                     Description
------                     -----------
--autoconfigure [Boolean]  Add autoconfigure compiler
                             transformations (default: true)
--classpath, -cp           Additional classpath entries
-e, --edit                 Open the file with the default system
                             editor
--no-guess-dependencies    Do not attempt to guess dependencies
--no-guess-imports         Do not attempt to guess imports
-q, --quiet                Quiet logging
-v, --verbose              Verbose logging of dependency
                             resolution
--watch                    Watch the specified file for changes

The version command provides a quick way to check which version of Spring Boot you are using, as follows:

$ spring version
Spring CLI v2.0.0.M7

63.1 Running Applications with the CLI

You can compile and run Groovy source code by using the run command. The Spring Boot CLI is completely self-contained, so you don’t need any external Groovy installation.

The following example shows a “hello world” web application written in Groovy:

hello.groovy.

@RestController
class WebApplication {
	@RequestMapping("/")
	String home() {
		"Hello World!"
To compile and run the application type the following command:
$ spring run hello.groovy
To pass command-line arguments to the application, use a -- to separate the commands
from the “spring” command arguments, as shown in the following example:
$ spring run hello.groovy -- --server.port=9000
To set JVM command line arguments, you can use the JAVA_OPTS environment variable, as
shown in the following example:
$ JAVA_OPTS=-Xmx1024m spring run hello.groovy
Note
When setting JAVA_OPTS on Microsoft Windows, make sure to quote the entire
instruction, such as set "JAVA_OPTS=-Xms256m -Xmx2048m". Doing so ensures the values
are properly passed to the process.63.1.1 Deduced “grab” Dependencies
Standard Groovy includes a @Grab annotation, which lets you declare dependencies on
third-party libraries. This useful technique lets Groovy download jars in the same way as
Maven or Gradle would but without requiring you to use a build tool.
Spring Boot extends this technique further and tries to deduce which libraries to “grab”
based on your code. For example, since the WebApplication code shown previously uses
@RestController annotations, Spring Boot grabs "Tomcat" and "Spring MVC".
The following items are used as “grab hints”:
Items Grabs
JdbcTemplate, NamedParameterJdbcTemplate, DataSource JDBC Application.
@EnableJms JMS Application.
@EnableCaching Caching abstraction.
@Test JUnit.
@EnableRabbit RabbitMQ.
@EnableReactor Project Reactor.
extends Specification Spock test.
@EnableBatchProcessing Spring Batch.
@MessageEndpoint @EnableIntegrationPatterns Spring Integration.
@Controller @RestController @EnableWebMvc Spring MVC + Embedded Tomcat.
@EnableWebSecurity Spring Security.
@EnableTransactionManagement Spring Transaction Management.




    
Tip
See subclasses of
CompilerAutoConfiguration
in the Spring Boot CLI source code to understand exactly how customizations are applied.
63.1.2 Deduced “grab” Coordinates
Spring Boot extends Groovy’s standard @Grab support by letting you specify a dependency
without a group or version (for example, @Grab('freemarker')). Doing so consults Spring
Boot’s default dependency metadata to deduce the artifact’s group and version. Note that
the default metadata is tied to the version of the CLI that you use – it changes only when
you move to a new version of the CLI, putting you in control of when the versions of your
dependencies may change. A table showing the dependencies and their versions that are
included in the default metadata can be found in the appendix.
63.1.3 Default Import Statements
To help reduce the size of your Groovy code, several import statements are automatically
included. Notice how the preceding example refers to @Component, @RestController, and
@RequestMapping without needing to use fully-qualified names or import statements.
Tip
Many Spring annotations work without using import statements. Try running your
application to see what fails before adding imports.
63.1.4 Automatic Main Method
Unlike the equivalent Java application, you do not need to include a
public static void main(String[] args) method with your Groovy scripts. A
SpringApplication is automatically created, with your compiled code acting as the
source.
63.1.5 Custom Dependency Management
By default, the CLI uses the dependency management declared in spring-boot-dependencies
when resolving @Grab dependencies. Additional dependency management, which overrides
the default dependency management, can be configured by using the
@DependencyManagementBom annotation. The annotation’s value should specify the
coordinates (groupId:artifactId:version) of one or more Maven BOMs.
For example, consider the following declaration:
@DependencyManagementBom("com.example.custom-bom:1.0.0")
The preceding declaration picks up custom-bom-1.0.0.pom in a Maven repository under
com/example/custom-versions/1.0.0/.
When you specify multiple BOMs, they are applied in the order in which you declare them,
as shown in the following example:
@DependencyManagementBom(["com.example.custom-bom:1.0.0",
		"com.example.another-bom:1.0.0"])
The preceding example indicates that dependency management in another-bom overrides the
dependency management in custom-bom.
You can use @DependencyManagementBom anywhere that you can use @Grab. However, to
ensure consistent ordering of the dependency management, you can use
@DependencyManagementBom at most once in your application. A useful source of dependency
management (which is a superset of Spring Boot’s dependency management) is the
Spring IO Platform, which you might include with the following
line:
@DependencyManagementBom('io.spring.platform:platform-bom:1.1.2.RELEASE')

63.2 Applications with Multiple Source Files

You can use “shell globbing” with all commands that accept file input. Doing so lets you use multiple files from a single directory, as shown in the following example:

$ spring run *.groovy

63.3 Packaging Your Application

You can use the jar command to package your application into a self-contained executable jar file, as shown in the following example:

$ spring jar my-app.jar *.groovy

The resulting jar contains the classes produced by compiling the application and all of the application’s dependencies so that it can then be run by using java -jar . The jar file also contains entries from the application’s classpath. You can add explicit paths to the jar by using --include and --exclude . Both are comma-separated, and both accept prefixes, in the form of “+” and “-”, to signify that they should be removed from the defaults. The default includes are as follows:

public/**, resources/**, static/**, templates/**, META-INF/**, *

The default excludes are as follows:

.*, repository/**, build/**, target/**, **/*.jar, **/*.groovy

Type spring help jar on the command line for more information.

63.4 Initialize a New Project

The init command lets you create a new project by using start.spring.io without leaving the shell, as shown in the following example:

$ spring init --dependencies=web,data-jpa my-project
Using service at https://start.spring.io
Project extracted to '/Users/developer/example/my-project'

The preceding example creates a my-project directory with a Maven-based project that uses spring-boot-starter-web and spring-boot-starter-data-jpa . You can list the capabilities of the service by using the --list flag, as shown in the following example:

$ spring init --list
=======================================
Capabilities of https://start.spring.io
=======================================
Available dependencies:
-----------------------
actuator - Actuator: Production ready features to help you monitor and manage your application
web - Web: Support for full-stack web development, including Tomcat and spring-webmvc
websocket - Websocket: Support for WebSocket development
ws - WS: Support for Spring Web Services
Available project types:
------------------------
gradle-build -  Gradle Config [format:build, build:gradle]
gradle-project -  Gradle Project [format:project, build:gradle]
maven-build -  Maven POM [format:build, build:maven]
maven-project -  Maven Project [format:project, build:maven] (default)
...

The init command supports many options. See the help output for more details. For instance, the following command creates a Gradle project that uses Java 8 and war packaging:

$ spring init --build=gradle --java-version=1.8 --dependencies=websocket --packaging=war sample-app.zip
Using service at https://start.spring.io
Content saved to 'sample-app.zip'

63.5 Using the Embedded Shell

Spring Boot includes command-line completion scripts for the BASH and zsh shells. If you do not use either of these shells (perhaps you are a Windows user), you can use the shell command to launch an integrated shell, as shown in the following example:

$ spring shell
Spring Boot (v2.0.0.M7)
Hit TAB to complete. Type \'help' and hit RETURN for help, and \'exit' to quit.

From inside the embedded shell, you can run other commands directly:

$ version
Spring CLI v2.0.0.M7

The embedded shell supports ANSI color output as well as tab completion. If you need to run a native command, you can use the ! prefix. To exit the embedded shell, press ctrl-c .

63.6 Adding Extensions to the CLI

You can add extensions to the CLI by using the install command. The command takes one or more sets of artifact coordinates in the format group:artifact:version , as shown in the following example:

$ spring install com.example:spring-boot-cli-extension:1.0.0.RELEASE

In addition to installing the artifacts identified by the coordinates you supply, all of the artifacts' dependencies are also installed.

To uninstall a dependency, use the uninstall command. As with the install command, it takes one or more sets of artifact coordinates in the format group:artifact:version , as shown in the following example:

$ spring uninstall com.example:spring-boot-cli-extension:1.0.0.RELEASE

It uninstalls the artifacts identified by the coordinates you supply and their dependencies.

To uninstall all additional dependencies, you can use the --all option, as shown in the following example:

$ spring uninstall --all

64. Developing Applications with the Groovy Beans DSL

Spring Framework 4.0 has native support for a beans{} “DSL” (borrowed from Grails ), and you can embed bean definitions in your Groovy application scripts by using the same format. This is sometimes a good way to include external features like middleware declarations, as shown in the following example:

@Configuration
class Application implements CommandLineRunner {
	@Autowired
	SharedService service
	@Override
	void run(String... args) {
		println service.message
import my.company.SharedService
beans {
	service(SharedService) {
		message = "Hello World"
}

You can mix class declarations with beans{} in the same file as long as they stay at the top level, or, if you prefer, you can put the beans DSL in a separate file.

65. Configuring the CLI with `settings.xml`

The Spring Boot CLI uses Aether, Maven’s dependency resolution engine, to resolve dependencies. The CLI makes use of the Maven configuration found in ~/.m2/settings.xml to configure Aether. The following configuration settings are honored by the CLI:

Offline
Mirrors
Servers
Proxies
Profiles
- Activation
- Repositories
Active profiles

See Maven’s settings documentation for further information.

66. What to Read Next

There are some sample groovy scripts available from the GitHub repository that you can use to try out the Spring Boot CLI. There is also extensive Javadoc throughout the source code .

If you find that you reach the limit of the CLI tool, you probably want to look at converting your application to a full Gradle or Maven built “Groovy project”. The next section covers Spring Boot’s " Build tool plugins ", which you can use with Gradle or Maven.

Part VIII. Build tool plugins

Spring Boot provides build tool plugins for Maven and Gradle. The plugins offer a variety of features, including the packaging of executable jars. This section provides more details on both plugins as well as some help should you need to extend an unsupported build system. If you are just getting started, you might want to read “ Chapter 13, Build Systems ” from the “ Part III, “Using Spring Boot” ” section first.

67. Spring Boot Maven Plugin

The Spring Boot Maven Plugin provides Spring Boot support in Maven, letting you package executable jar or war archives and run an application “in-place”. To use it, you must use Maven 3.2 (or later).

	Note
	See the Spring Boot Maven Plugin Site for complete plugin documentation.

67.1 Including the Plugin

To use the Spring Boot Maven Plugin, include the appropriate XML in the plugins section of your pom.xml , as shown in the following example:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<!-- ... -->
	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
				<version>2.0.0.M7</version>
				<executions>
					<execution>
						<goals>
							<goal>repackage</goal>
						</goals>
					</execution>
				</executions>
			</plugin>
		</plugins>
	</build>
</project>

The preceding configuration repackages a jar or war that is built during the package phase of the Maven lifecycle. The following example shows both the repackaged jar as well as the original jar in the target directory:

$ mvn package
$ ls target/*.jar
target/myproject-1.0.0.jar target/myproject-1.0.0.jar.original

If you do not include the <execution/> configuration as shown in the prior example, you can run the plugin on its own (but only if the package goal is used as well). For example:

$ mvn package spring-boot:repackage
$ ls target/*.jar
target/myproject-1.0.0.jar target/myproject-1.0.0.jar.original

If you use a milestone or snapshot release, you also need to add the appropriate pluginRepository elements as shown in the following listing:

<pluginRepositories>
	<pluginRepository>
		<id>spring-snapshots</id>
		<url>http://repo.spring.io/snapshot</url>
	</pluginRepository>
	<pluginRepository>
		<id>spring-milestones</id>
		<url>http://repo.spring.io/milestone</url>
	</pluginRepository>
</pluginRepositories>

67.2 Packaging Executable Jar and War Files

Once spring-boot-maven-plugin has been included in your pom.xml , it automatically tries to rewrite archives to make them executable by using the spring-boot:repackage goal. You should configure your project to build a jar or war (as appropriate) by using the usual packaging element, as shown in the following example:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<!-- ... -->
	<packaging>jar</packaging>
	<!-- ... -->
</project>

Your existing archive is enhanced by Spring Boot during the package phase. The main class that you want to launch can either be specified by using a configuration option or by adding a Main-Class attribute to the manifest in the usual way. If you do not specify a main class, the plugin searches for a class with a public static void main(String[] args) method.

To build and run a project artifact, you can type the following:

$ mvn package
$ java -jar target/mymodule-0.0.1-SNAPSHOT.jar

To build a war file that is both executable and deployable into an external container, you need to mark the embedded container dependencies as “provided”, as shown in the following example:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<!-- ... -->
	<packaging>war</packaging>
	<!-- ... -->
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-tomcat</artifactId>
			<scope>provided</scope>
		</dependency>
		<!-- ... -->
	</dependencies>
</project>

	Tip
	See the “ Section 86.1, “Create a Deployable War File” ” section for more details on how to create a deployable war file.

Advanced configuration options and examples are available in the plugin info page .

68. Spring Boot Gradle Plugin

The Spring Boot Gradle Plugin provides Spring Boot support in Gradle, letting you package executable jar or war archives, run Spring Boot applications, and use the dependency management provided by spring-boot-dependencies . It requires Gradle 4.0 or later. Please refer to the plugin’s documentation to learn more:

Reference ( HTML and PDF )
API

69. Spring Boot AntLib Module

The Spring Boot AntLib module provides basic Spring Boot support for Apache Ant. You can use the module to create executable jars. To use the module, you need to declare an additional spring-boot namespace in your build.xml , as shown in the following example:

<project xmlns:ivy="antlib:org.apache.ivy.ant"
	xmlns:spring-boot="antlib:org.springframework.boot.ant"
	name="myapp" default="build">
</project>

You need to remember to start Ant using the -lib option, as shown in the following example:

$ ant -lib <folder containing spring-boot-antlib-2.0.0.M7.jar>

	Tip
	The “Using Spring Boot” section includes a more complete example of using Apache Ant with `spring-boot-antlib` .

69.1 Spring Boot Ant Tasks

Once the spring-boot-antlib namespace has been declared, the following additional tasks are available:

Section 69.1.1, “ spring-boot:exejar ”
Section 69.2, “ spring-boot:findmainclass ”

69.1.1 `spring-boot:exejar`

You can use the exejar task to create a Spring Boot executable jar. The following attributes are supported by the task:

Attribute	Description	Required
`destfile`	The destination jar file to create	Yes
`classes`	The root directory of Java class files	Yes
`start-class`	The main application class to run	No (default is first class found declaring a `main` method)

The following nested elements can be used with the task:

Element	Description
`resources`	One or more Resource Collections describing a set of Resources that should be added to the content of the created jar file.
`lib`	One or more Resource Collections that should be added to the set of jar libraries that make up the runtime dependency classpath of the application.

69.1.2 Examples

Specify start-class.

<spring-boot:exejar destfile="target/my-application.jar"
		classes="target/classes" start-class="com.foo.MyApplication">
	<resources>
		<fileset dir="src/main/resources" />
	</resources>
		<fileset dir="lib" />
</spring-boot:exejar>

Detect start-class.

<exejar destfile="target/my-application.jar" classes="target/classes">
		<fileset dir="lib" />
</exejar>

69.2 `spring-boot:findmainclass`

The findmainclass task is used internally by exejar to locate a class declaring a main . You can also use this task directly in your build, if needed. The following attributes are supported:

Attribute	Description	Required
`classesroot`	The root directory of Java class files	Yes (unless `mainclass` is specified)
`mainclass`	Can be used to short-circuit the `main` class search	No
`property`	The Ant property that should be set with the result	No (result will be logged if unspecified)

69.2.1 Examples

Find and log.

<findmainclass classesroot="target/classes" />

Find and set.

<findmainclass classesroot="target/classes" property="main-class" />

Override and set.

<findmainclass mainclass="com.foo.MainClass" property="main-class" />

70. Supporting Other Build Systems

If you want to use a build tool other than Maven, Gradle, or Ant, you likely need to develop your own plugin. Executable jars need to follow a specific format and certain entries need to be written in an uncompressed form (see the “ executable jar format ” section in the appendix for details).

The Spring Boot Maven and Gradle plugins both make use of spring-boot-loader-tools to actually generate jars. If you need to, you may use this library directly.

70.1 Repackaging Archives

To repackage an existing archive so that it becomes a self-contained executable archive, use org.springframework.boot.loader.tools.Repackager . The Repackager class takes a single constructor argument that refers to an existing jar or war archive. Use one of the two available repackage() methods to either replace the original file or write to a new destination. Various settings can also be configured on the repackager before it is run.

70.2 Nested Libraries

When repackaging an archive, you can include references to dependency files by using the org.springframework.boot.loader.tools.Libraries interface. We do not provide any concrete implementations of Libraries here as they are usually build-system-specific.

If your archive already includes libraries, you can use Libraries.NONE .

70.3 Finding a Main Class

If you do not use Repackager.setMainClass() to specify a main class, the repackager uses ASM to read class files and tries to find a suitable class with a public static void main(String[] args) method. An exception is thrown if more than one candidate is found.

70.4 Example Repackage Implementation

The following listing shows a typical example repackage:

Repackager repackager = new Repackager(sourceJarFile);
repackager.setBackupSource(false);
repackager.repackage(new Libraries() {
			@Override
			public void doWithLibraries(LibraryCallback callback) throws IOException {
				// Build system specific implementation, callback for each dependency
				// callback.library(new Library(nestedFile, LibraryScope.COMPILE));
		});

71. What to Read Next

If you are interested in how the build tool plugins work, you can look at the spring-boot-tools module on GitHub. More technical details of the executable jar format are covered in the appendix .

If you have specific build-related questions, you can check out the “ how-to ” guides.

Part IX. ‘How-to’ guides

This section provides answers to some common ‘how do I do that…’ questions that often arise when using Spring Boot. Its coverage is not exhaustive, but it does cover quite a lot.

If you have a specific problem that we do not cover here, you might want to check out stackoverflow.com to see if someone has already provided an answer. This is also a great place to ask new questions (please use the spring-boot tag).

We are also more than happy to extend this section. If you want to add a ‘how-to’, send us a pull request .

72. Spring Boot Application

72.1 Create Your Own FailureAnalyzer

FailureAnalyzer is a great way to intercept an exception on startup and turn it into a human-readable message, wrapped in a FailureAnalysis . Spring Boot provides such an analyzer for application-context-related exceptions, JSR-303 validations, and more. You can also create your own.

AbstractFailureAnalyzer is a convenient extension of FailureAnalyzer that checks the presence of a specified exception type in the exception to handle. You can extend from that so that your implementation gets a chance to handle the exception only when it is actually present. If, for whatever reason, you cannot handle the exception, return null to give another implementation a chance to handle the exception.

FailureAnalyzer implementations must be registered in META-INF/spring.factories . The following example registers ProjectConstraintViolationFailureAnalyzer :

org.springframework.boot.diagnostics.FailureAnalyzer=\
com.example.ProjectConstraintViolationFailureAnalyzer

72.2 Troubleshoot Auto-configuration

The Spring Boot auto-configuration tries its best to ‘do the right thing’, but sometimes things fail, and it can be hard to tell why.

There is a really useful ConditionEvaluationReport available in any Spring Boot ApplicationContext . You can see it if you enable DEBUG logging output. If you use the spring-boot-actuator , there is also a conditions endpoint that renders the report in JSON. Use that endpoint to debug the application and see what features have been added (and which not) by Spring Boot at runtime.

Many more questions can be answered by looking at the source code and the Javadoc. When reading the code, remember the following rules of thumb:

Look for classes called *AutoConfiguration and read their sources. Pay special attention to the @Conditional* annotations to find out what features they enable and when. Add --debug to the command line or a System property -Ddebug to get a log on the console of all the auto-configuration decisions that were made in your app. In a running Actuator app, look at the conditions endpoint ( /actuator/conditions or the JMX equivalent) for the same information.
Look for classes that are @ConfigurationProperties (such as ServerProperties ) and read from there the available external configuration options. The @ConfigurationProperties has a name attribute that acts as a prefix to external properties. Thus, ServerProperties has prefix="server" and its configuration properties are server.port , server.address , and others. In a running Actuator app, look at the configprops endpoint.
Look for uses of the bind method on the Binder to pull configuration values explicitly out of the Environment in a relaxed manner. It is often used with a prefix.
Look for @Value annotations that bind directly to the Environment .
Look for @ConditionalOnExpression annotations that switch features on and off in response to SpEL expressions, normally evaluated with placeholders resolved from the Environment .

72.3 Customize the Environment or ApplicationContext Before It Starts

A SpringApplication has ApplicationListeners and ApplicationContextInitializers that are used to apply customizations to the context or environment. Spring Boot loads a number of such customizations for use internally from META-INF/spring.factories . There is more than one way to register additional ones:

Programmatically, per application, by calling the addListeners and addInitializers methods on SpringApplication before you run it.
Declaratively, per application, by setting the context.initializer.classes or context.listener.classes properties.
Declaratively, for all applications, by adding a META-INF/spring.factories and packaging a jar file that the applications all use as a library.

The SpringApplication sends some special ApplicationEvents to the listeners (some even before the context is created) and then registers the listeners for events published by the ApplicationContext as well. See “ Section 23.5, “Application Events and Listeners” ” in the ‘Spring Boot features’ section for a complete list.

It is also possible to customize the Environment before the application context is refreshed by using EnvironmentPostProcessor . Each implementation should be registered in META-INF/spring.factories , as shown in the following example:

org.springframework.boot.env.EnvironmentPostProcessor=com.example.YourEnvironmentPostProcessor

The implementation can load arbitrary files and add them to the Environment . For instance, the following example loads a YAML configuration file from the classpath:

public class EnvironmentPostProcessorExample implements EnvironmentPostProcessor {
	private final YamlPropertySourceLoader loader = new YamlPropertySourceLoader();
	@Override
	public void postProcessEnvironment(ConfigurableEnvironment environment,
			SpringApplication application) {
		Resource path = new ClassPathResource("com/example/myapp/config.yml");
		PropertySource<?> propertySource = loadYaml(path);
		environment.getPropertySources().addLast(propertySource);
	private PropertySource<?> loadYaml(Resource path) {
		if (!path.exists()) {
			throw new IllegalArgumentException("Resource " + path + " does not exist");
		try {
			return this.loader.load("custom-resource", path, null);
		catch (IOException ex) {
			throw new IllegalStateException(
					"Failed to load yaml configuration from " + path, ex);
}

	Tip
	The `Environment` has already been prepared with all the usual property sources that Spring Boot loads by default. It is therefore possible to get the location of the file from the environment. This example adds the `custom-resource` property source at the end of the list so that a key defined in any of the usual other locations takes precedence. A custom implementation may define another order.

	Caution
	While using `@PropertySource` on your `@SpringBootApplication` may seem convenient and easy enough to load a custom resource in the `Environment` , we do not recommend it as Spring Boot prepares the `Environment` before the `ApplicationContext` is refreshed. Any key defined via `@PropertySource` is loaded too late to have any effect on auto-configuration.

72.4 Build an ApplicationContext Hierarchy (Adding a Parent or Root Context)

You can use the ApplicationBuilder class to create parent/child ApplicationContext hierarchies. See “ Section 23.4, “Fluent Builder API” ” in the ‘Spring Boot features’ section for more information.

72.5 Create a Non-web Application

Not all Spring applications have to be web applications (or web services). If you want to execute some code in a main method but also bootstrap a Spring application to set up the infrastructure to use, you can use the SpringApplication features of Spring Boot. A SpringApplication changes its ApplicationContext class, depending on whether it thinks it needs a web application or not. The first thing you can do to help it is to leave the servlet API dependencies off the classpath. If you cannot do that (for example, you run two applications from the same code base) then you can explicitly call setWebEnvironment(false) on your SpringApplication instance or set the applicationContextClass property (through the Java API or with external properties). Application code that you want to run as your business logic can be implemented as a CommandLineRunner and dropped into the context as a @Bean definition.

73. Properties and Configuration

73.1 Automatically Expand Properties at Build Time

Rather than hardcoding some properties that are also specified in your project’s build configuration, you can automatically expand them by instead using the existing build configuration. This is possible in both Maven and Gradle.

73.1.1 Automatic Property Expansion Using Maven

You can automatically expand properties from the Maven project by using resource filtering. If you use the spring-boot-starter-parent , you can then refer to your Maven ‘project properties’ with @..@ placeholders, as shown in the following example:

app.encoding[email protected]@
app.java.version[email protected]@

	Note
	Only production configuration is filtered that way (in other words, no filtering is applied on `src/test/resources` ).

	Tip
	If you enable the `addResources` flag, the `spring-boot:run` goal can add `src/main/resources` directly to the classpath (for hot reloading purposes). Doing so circumvents the resource filtering and this feature. Instead, you can use the `exec:java` goal or customize the plugin’s configuration, see the plugin usage page for more details.

If you do not use the starter parent, you need to include the following element inside the <build/> element of your pom.xml :

<resources>
	<resource>
		<directory>src/main/resources</directory>
		<filtering>true</filtering>
	</resource>
</resources>

You also need to include the following element inside <plugins/> :

<plugin>
	<groupId>org.apache.maven.plugins</groupId>
	<artifactId>maven-resources-plugin</artifactId>
	<version>2.7</version>
	<configuration>
		<delimiters>
			<delimiter>@</delimiter>
		</delimiters>
		<useDefaultDelimiters>false</useDefaultDelimiters>
	</configuration>
</plugin>

	Note
	The `useDefaultDelimiters` property is important if you use standard Spring placeholders (such as `${placeholder}` ) in your configuration. If that property is not set to `false` , these may be expanded by the build.

73.1.2 Automatic Property Expansion Using Gradle

You can automatically expand properties from the Gradle project by configuring the Java plugin’s processResources task to do so, as shown in the following example:

processResources {
	expand(project.properties)
}

You can then refer to your Gradle project’s properties via placeholders, as shown in the following example:

app.name=${name}
app.description=${description}

	Note
	Gradle’s `expand` method uses Groovy’s `SimpleTemplateEngine` , which transforms `${..}` tokens. The `${..}` style conflicts with Spring’s own property placeholder mechanism. To use Spring property placeholders together with automatic expansion, escape the Spring property placeholders as follows: `\${..}` .

73.2 Externalize the Configuration of SpringApplication

A SpringApplication has bean properties (mainly setters), so you can use its Java API as you create the application to modify its behavior. Alternatively, you can externalize the configuration using properties in spring.main.* . For example, in application.properties , you might have the following settings:

spring.main.web-environment=false
spring.main.banner-mode=off

Then the Spring Boot banner is not printed on startup, and the application is not a web application.

	Note
	The preceding example also demonstrates how flexible binding allows the use of underscores ( `_` ) as well as dashes ( `-` ) in property names.

Properties defined in external configuration overrides the values specified with the Java API, with the notable exception of the sources used to create the ApplicationContext . Consider the following application:

new SpringApplicationBuilder()
	.bannerMode(Banner.Mode.OFF)
	.sources(demo.MyApp.class)
	.run(args);

Now consider the following configuration:

spring.main.sources=com.acme.Config,com.acme.ExtraConfig
spring.main.banner-mode=console

The actual application now shows the banner (as overridden by configuration) and uses three sources for the ApplicationContext (in the following order): demo.MyApp , com.acme.Config , com.acme.ExtraConfig .

73.3 Change the Location of External Properties of an Application

By default, properties from different sources are added to the Spring Environment in a defined order (see “ Chapter 24, Externalized Configuration ” in the ‘Spring Boot features’ section for the exact order).

A nice way to augment and modify this ordering is to add @PropertySource annotations to your application sources. Classes passed to the SpringApplication static convenience methods and those added using setSources() are inspected to see if they have @PropertySources . If they do, those properties are added to the Environment early enough to be used in all phases of the ApplicationContext lifecycle. Properties added in this way have lower priority than any added by using the default locations (such as application.properties ), system properties, environment variables, or the command line.

You can also provide the following System properties (or environment variables) to change the behavior:

spring.config.name ( SPRING_CONFIG_NAME ): Defaults to application as the root of the file name.
spring.config.location ( SPRING_CONFIG_LOCATION ): The file to load (such as a classpath resource or a URL). A separate Environment property source is set up for this document and it can be overridden by system properties, environment variables, or the command line.

No matter what you set in the environment, Spring Boot always loads application.properties as described above. By default, if YAML is used, then files with the ‘.yml’ extension are also added to the list.

Spring Boot logs the configuration files that are loaded at the DEBUG level and the candidates it has not found at TRACE level.

See ConfigFileApplicationListener for more detail.

73.4 Use ‘Short’ Command Line Arguments

Some people like to use (for example) --port=9000 instead of --server.port=9000 to set configuration properties on the command line. You can enable this behavior by using placeholders in application.properties , as shown in the following example:

server.port=${port:8080}

Tip

If you inherit from the spring-boot-starter-parent POM, the default filter token of the maven-resources-plugins has been changed from ${*} to @ (that is, @maven.token@ instead of ${maven.token} ) to prevent conflicts with Spring-style placeholders. If you have enabled maven filtering for the application.properties directly, you may want to also change the default filter token to use other delimiters .

	Note
	In this specific case, the port binding works in a PaaS environment such as Heroku or Cloud Foundry In those two platforms, the `PORT` environment variable is set automatically and Spring can bind to capitalized synonyms for `Environment` properties.

73.5 Use YAML for External Properties

YAML is a superset of JSON and, as such, is a convenient syntax for storing external properties in a hierarchical format, as shown in the following example:

spring:
	application:
		name: cruncher
	datasource:
		driverClassName: com.mysql.jdbc.Driver
		url: jdbc:mysql://localhost/test
server:
	port: 9000

Create a file called application.yml and put it in the root of your classpath. Then add snakeyaml to your dependencies (Maven coordinates org.yaml:snakeyaml , already included if you use the spring-boot-starter ). A YAML file is parsed to a Java Map<String,Object> (like a JSON object), and Spring Boot flattens the map so that it is one level deep and has period-separated keys, as many people are used to with Properties files in Java.

The example YAML above corresponds to an application.properties file as follows:

spring.application.name=cruncher
spring.datasource.driverClassName=com.mysql.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost/test
server.port=9000

See “ Section 24.6, “Using YAML Instead of Properties” ” in the ‘Spring Boot features’ section for more information about YAML.

73.6 Set the Active Spring Profiles

The Spring Environment has an API for this, but you would normally set a System property ( spring.profiles.active ) or an OS environment variable ( SPRING_PROFILES_ACTIVE ). Also, you can launch your application with a -D argument (remember to put it before the main class or jar archive), as follows:

$ java -jar -Dspring.profiles.active=production demo-0.0.1-SNAPSHOT.jar

In Spring Boot, you can also set the active profile in application.properties , as shown in the following example:

spring.profiles.active=production

A value set this way is replaced by the System property or environment variable setting but not by the SpringApplicationBuilder.profiles() method. Thus, the latter Java API can be used to augment the profiles without changing the defaults.

See “ Chapter 25, Profiles ” in the “Spring Boot features” section for more information.

73.7 Change Configuration Depending on the Environment

A YAML file is actually a sequence of documents separated by --- lines, and each document is parsed separately to a flattened map.

If a YAML document contains a spring.profiles key, then the profiles value (a comma-separated list of profiles) is fed into the Spring Environment.acceptsProfiles() method. If any of those profiles is active, that document is included in the final merge (otherwise not), as shown in the following example:

server:
	port: 9000
spring:
	profiles: development
server:
	port: 9001
spring:
	profiles: production
server:
	port: 0

In the preceding example, the default port is 9000. However, if the Spring profile called ‘development’ is active, then the port is 9001. If ‘production’ is active, then the port is 0.

The YAML documents are merged in the order in which they are encountered (so later values override earlier ones).

To do the same thing with properties files, you can use application-${profile}.properties to specify profile-specific values.

73.8 Discover Built-in Options for External Properties

Spring Boot binds external properties from application.properties (or .yml ) (and other places) into an application at runtime. There is not (and technically cannot be) an exhaustive list of all supported properties in a single location, because contributions can come from additional jar files on your classpath.

A running application with the Actuator features has a configprops endpoint that shows all the bound and bindable properties available through @ConfigurationProperties .

The appendix includes an application.properties example with a list of the most common properties supported by Spring Boot. The definitive list comes from searching the source code for @ConfigurationProperties and @Value annotations as well as the occasional use of Binder .

74. Embedded Web Servers

Each Spring Boot web application includes an embedded web server. This feature leads to a number of how-to questions, including how to change the embedded server and how to configure the embedded server. This section answers those questions.

74.1 Use Another Web Server

Many Spring Boot starters include default embedded containers. spring-boot-starter-web includes Tomcat by including spring-boot-starter-tomcat , but you can use spring-boot-starter-jetty and spring-boot-starter-undertow instead. spring-boot-starter-webflux includes Reactor Netty by including spring-boot-starter-reactor-netty , but you can use spring-boot-starter-tomcat , spring-boot-starter-jetty , and spring-boot-starter-undertow instead.

	Note
	Many starters support only Spring MVC, so they transitively bring `spring-boot-starter-web` into your application classpath.

If you need to use a different HTTP server, you need to exclude the default dependencies and include the one you need. Spring Boot provides separate starters for HTTP servers to help make this process as easy as possible.

The following Maven example shows how to exclude Tomcat and include Jetty for Spring MVC:

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-web</artifactId>
	<exclusions>
		<!-- Exclude the Tomcat dependency -->
		<exclusion>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-tomcat</artifactId>
		</exclusion>
	</exclusions>
</dependency>
<!-- Use Jetty instead -->
<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-jetty</artifactId>
</dependency>

The following Gradle example shows how to exclude Netty and include Undertow for Spring WebFlux:

configurations {
	// exclude Reactor Netty
	compile.exclude module: 'spring-boot-starter-reactor-netty'
dependencies {
	compile 'org.springframework.boot:spring-boot-starter-webflux'
	// Use Undertow instead
	compile 'org.springframework.boot:spring-boot-starter-undertow'
	// ...
}

	Note
	`spring-boot-starter-reactor-netty` is required to use the `WebClient` class, so you may need to keep a dependency on Netty even when you need to include a different HTTP server.

74.2 Configure Jetty

Generally, you can follow the advice from “ Section 73.8, “Discover Built-in Options for External Properties” ” about @ConfigurationProperties ( ServerProperties is the main one here). However, you should also look at ServletWebServerFactoryCustomizer . The Jetty APIs are quite rich, so, once you have access to the JettyServletWebServerFactory , you can modify it in a number of ways. Alternatively, if you need more control and customization, you can add your own JettyServletWebServerFactory .

74.3 Add a Servlet, Filter, or Listener to an Application

There are two ways to add Servlet , Filter , ServletContextListener , and the other listeners supported by the Servlet spec to your application. You can either provide Spring beans for them or enable scanning for Servlet components.

74.3.1 Add a Servlet, Filter, or Listener by Using a Spring Bean

To add a Servlet , Filter , or Servlet *Listener by using a Spring bean, you must provide a @Bean definition for it. Doing so can be very useful when you want to inject configuration or dependencies. However, you must be very careful that they do not cause eager initialization of too many other beans, because they have to be installed in the container very early in the application lifecycle (for example, it is not a good idea to have them depend on your DataSource or JPA configuration). You can work around restrictions like that by initializing the beans lazily when first used instead of on initialization.

In the case of Filters and Servlets , you can also add mappings and init parameters by adding a FilterRegistrationBean or a ServletRegistrationBean instead of or in addition to the underlying component.

	Note
	If no `dispatcherType` is specified on a filter registration, `REQUEST` is used. This aligns with the Servlet Specification’s default dispatcher type.

Disable Registration of a Servlet or Filter

As described above , any Servlet or Filter beans are registered with the servlet container automatically. To disable registration of a particular Filter or Servlet bean, create a registration bean for it and mark it as disabled, as shown in the following example:

@Bean
public FilterRegistrationBean registration(MyFilter filter) {
	FilterRegistrationBean registration = new FilterRegistrationBean(filter);
	registration.setEnabled(false);
	return registration;
}

74.3.2 Add Servlets, Filters, and Listeners by Using Classpath Scanning

@WebServlet , @WebFilter , and @WebListener annotated classes can be automatically registered with an embedded servlet container by annotating a @Configuration class with @ServletComponentScan and specifying the package(s) containing the components that you want to register. By default, @ServletComponentScan scans from the package of the annotated class.

74.4 Change the HTTP Port

In a standalone application, the main HTTP port defaults to 8080 but can be set with server.port (for example, in application.properties or as a System property). Thanks to relaxed binding of Environment values, you can also use SERVER_PORT (for example, as an OS environment variable).

To switch off the HTTP endpoints completely but still create a WebApplicationContext , use server.port=-1 . (Doing so is sometimes useful for testing.)

For more details, see “ Section 27.4.4, “Customizing Embedded Servlet Containers” ” in the ‘Spring Boot features’ section, or the ServerProperties source code.

74.5 Use a Random Unassigned HTTP Port

To scan for a free port (using OS natives to prevent clashes) use server.port=0 .

74.6 Discover the HTTP Port at Runtime

You can access the port the server is running on from log output or from the ServletWebServerApplicationContext through its EmbeddedWebServer . The best way to get that and be sure that it has been initialized is to add a @Bean of type ApplicationListener<ServletWebServerInitializedEvent> and pull the container out of the event when it is published.

Tests that use @SpringBootTest(webEnvironment=WebEnvironment.RANDOM_PORT) can also inject the actual port into a field by using the @LocalServerPort annotation, as shown in the following example:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest(webEnvironment=WebEnvironment.RANDOM_PORT)
public class MyWebIntegrationTests {
	@Autowired
	ServletWebServerApplicationContext server;
	@LocalServerPort
	int port;
	// ...
}

	Note
	`@LocalServerPort` is a meta-annotation for `@Value("${local.server.port}")` . Do not try to inject the port in a regular application. As we just saw, the value is set only after the container has been initialized. Contrary to a test, application code callbacks are processed early (before the value is actually available).

74.7 Configure SSL

SSL can be configured declaratively by setting the various server.ssl.* properties, typically in application.properties or application.yml . The following example shows setting SSL properties in application.properties :

server.port=8443
server.ssl.key-store=classpath:keystore.jks
server.ssl.key-store-password=secret
server.ssl.key-password=another-secret

See Ssl for details of all of the supported properties.

Using configuration such as the preceding example means the application no longer supports a plain HTTP connector at port 8080. Spring Boot does not support the configuration of both an HTTP connector and an HTTPS connector through application.properties . If you want to have both, you need to configure one of them programmatically. We recommend using application.properties to configure HTTPS, as the HTTP connector is the easier of the two to configure programmatically. See the spring-boot-sample-tomcat-multi-connectors sample project for an example.

74.8 Configure HTTP/2

You can enable HTTP/2 support in your Spring Boot application with the server.http2.enabled configuration property. This support depends on the chosen web server and the application environment, since that protocol is not supported out-of-the-box by JDK8.

	Note
	Spring Boot does not support `h2c` , the cleartext version of the HTTP/2 protocol. So you must configure configure SSL first .

Currently, only Undertow and Tomcat are supported with this configuration key.

74.8.1 HTTP/2 with Undertow

As of Undertow 1.4.0+, HTTP/2 is supported without any additional requirement on JDK8.

74.8.2 HTTP/2 with Tomcat

Spring Boot ships by default with Tomcat 8.5.x; with that version, HTTP/2 is only supported if the libtcnative library and its dependencies are installed on the host operating system.

The library folder must be made available, if not already, to the JVM library path; this can be done with a JVM argument such as -Djava.library.path=/usr/local/opt/tomcat-native/lib . More on this in the official Tomcat documentation .

Starting Tomcat 8.5.x without that native support will log the following error:

ERROR 8787 --- [           main] o.a.coyote.http11.Http11NioProtocol      : The upgrade handler [org.apache.coyote.http2.Http2Protocol] for [h2] only supports upgrade via ALPN but has been configured for the ["https-jsse-nio-8443"] connector that does not support ALPN.

This error is not fatal, and the application starts with HTTP/1.1 SSL support still.

Running your application with Tomcat 9.0.x and JDK9 doesn’t require any native library installed. To use Tomcat 9, you can override the tomcat.version build property with the version of your choice.

74.9 Configure Access Logging

Access logs can be configured for Tomcat, Undertow, and Jetty through their respective namespaces.

For instance, the following settings log access on Tomcat with a custom pattern .

server.tomcat.basedir=my-tomcat
server.tomcat.accesslog.enabled=true
server.tomcat.accesslog.pattern=%t %a "%r" %s (%D ms)

	Note
	The default location for logs is a `logs` directory relative to the Tomcat base directory. By default, the `logs` directory is a temporary directory, so you may want to fix Tomcat’s base directory or use an absolute path for the logs. In the preceding example, the logs are available in `my-tomcat/logs` relative to the working directory of the application.

Access logging for undertow can be configured in a similar fashion, as shown in the following example:

server.undertow.accesslog.enabled=true
server.undertow.accesslog.pattern=%t %a "%r" %s (%D ms)

Logs are stored in a logs directory relative to the working directory of the application. You can customize this location by setting the server.undertow.accesslog.directory property.

Finally, access logging for Jetty can also be configured as follows:

server.jetty.accesslog.enabled=true
server.jetty.accesslog.filename=/var/log/jetty-access.log

By default, logs are redirected to System.err . For more details, see the documentation .

74.10 Running Behind a Front-end Proxy Server

Your application might need to send 302 redirects or render content with absolute links back to itself. When running behind a proxy, the caller wants a link to the proxy and not to the physical address of the machine hosting your app. Typically, such situations are handled through a contract with the proxy, which adds headers to tell the back end how to construct links to itself.

If the proxy adds conventional X-Forwarded-For and X-Forwarded-Proto headers (most proxy server do so), the absolute links should be rendered correctly, provided server.use-forward-headers is set to true in your application.properties .

	Note
	If your application runs in Cloud Foundry or Heroku, the `server.use-forward-headers` property defaults to `true` . In all other instances, it defaults to `false` .

74.10.1 Customize Tomcat’s Proxy Configuration

If you use Tomcat, you can additionally configure the names of the headers used to carry “forwarded” information, as shown in the following example:

server.tomcat.remote-ip-header=x-your-remote-ip-header
server.tomcat.protocol-header=x-your-protocol-header

Tomcat is also configured with a default regular expression that matches internal proxies that are to be trusted. By default, IP addresses in 10/8 , 192.168/16 , 169.254/16 and 127/8 are trusted. You can customize the valve’s configuration by adding an entry to application.properties , as shown in the following example:

server.tomcat.internal-proxies=192\\.168\\.\\d{1,3}\\.\\d{1,3}

	Note
	The double backslashes are required only when you use a properties file for configuration. If you use YAML, single backslashes are sufficient, and a value equivalent to that shown in the preceding example would be `192\.168\.\d{1,3}\.\d{1,3}` .

	Note
	You can trust all proxies by setting the `internal-proxies` to empty (but do not do so in production).

You can take complete control of the configuration of Tomcat’s RemoteIpValve by switching the automatic one off (to do so, set server.use-forward-headers=false ) and adding a new valve instance in a TomcatServletWebServerFactory bean.

74.11 Configure Tomcat

Generally, you can follow the advice from “ Section 73.8, “Discover Built-in Options for External Properties” ” about @ConfigurationProperties ( ServerProperties is the main one here). However, you should also look at ServletWebServerFactoryCustomizer and various Tomcat-specific *Customizers that you can add. The Tomcat APIs are quite rich, so, once you have access to the TomcatServletWebServerFactory , you can modify it in a number of ways. Alternatively, if you need more control and customization, you can add your own TomcatServletWebServerFactory .

74.12 Enable Multiple Connectors with Tomcat

You can add an org.apache.catalina.connector.Connector to the TomcatServletWebServerFactory , which can allow multiple connectors, including HTTP and HTTPS connectors, as shown in the following example:

@Bean
public ServletWebServerFactory servletContainer() {
	TomcatServletWebServerFactory tomcat = new TomcatServletWebServerFactory();
	tomcat.addAdditionalTomcatConnectors(createSslConnector());
	return tomcat;
private Connector createSslConnector() {
	Connector connector = new Connector("org.apache.coyote.http11.Http11NioProtocol");
	Http11NioProtocol protocol = (Http11NioProtocol) connector.getProtocolHandler();
	try {
		File keystore = new ClassPathResource("keystore").getFile();
		File truststore = new ClassPathResource("keystore").getFile();
		connector.setScheme("https");
		connector.setSecure(true);
		connector.setPort(8443);
		protocol.setSSLEnabled(true);
		protocol.setKeystoreFile(keystore.getAbsolutePath());
		protocol.setKeystorePass("changeit");
		protocol.setTruststoreFile(truststore.getAbsolutePath());
		protocol.setTruststorePass("changeit");
		protocol.setKeyAlias("apitester");
		return connector;
	catch (IOException ex) {
		throw new IllegalStateException("can't access keystore: [" + "keystore"
				+ "] or truststore: [" + "keystore" + "]", ex);
}

74.13 Use Tomcat’s LegacyCookieProcessor

By default, the embedded Tomcat used by Spring Boot does not support "Version 0" of the Cookie format, so you may see the following error:

java.lang.IllegalArgumentException: An invalid character [32] was present in the Cookie value

If at all possible, you should consider updating your code to only store values compliant with later Cookie specifications. If, however, you cannot change the way that cookies are written, you can instead configure Tomcat to use a LegacyCookieProcessor . To switch to the LegacyCookieProcessor , use an ServletWebServerFactoryCustomizer bean that adds a TomcatContextCustomizer , as shown in the following example:

@Bean
public WebServerFactoryCustomizer<TomcatServletWebServerFactory> cookieProcessorCustomizer() {
	return (serverFactory) -> serverFactory.addContextCustomizers(
			(context) -> context.setCookieProcessor(new LegacyCookieProcessor()));
}

74.14 Configure Undertow

Generally you can follow the advice from “ Section 73.8, “Discover Built-in Options for External Properties” ” about @ConfigurationProperties ( ServerProperties and ServerProperties.Undertow are the main ones here). However, you should also look at ServletWebServerFactoryCustomizer . Once you have access to the UndertowServletWebServerFactory , you can use an UndertowBuilderCustomizer to modify Undertow’s configuration to meet your needs. Alternatively, if you need more control and customization, you can add your own UndertowServletWebServerFactory .

74.15 Enable Multiple Listeners with Undertow

Add an UndertowBuilderCustomizer to the UndertowServletWebServerFactory and add a listener to the Builder , as shown in the following example:

@Bean
public UndertowServletWebServerFactory servletWebServerFactory() {
	UndertowServletWebServerFactory factory = new UndertowServletWebServerFactory();
	factory.addBuilderCustomizers(new UndertowBuilderCustomizer() {
		@Override
		public void customize(Builder builder) {
			builder.addHttpListener(8080, "0.0.0.0");
	return factory;
}

74.16 Create WebSocket Endpoints Using @ServerEndpoint

If you want to use @ServerEndpoint in a Spring Boot application that used an embedded container, you must declare a single ServerEndpointExporter @Bean , as shown in the following example:

@Bean
public ServerEndpointExporter serverEndpointExporter() {
	return new ServerEndpointExporter();
}

The bean shown in the preceding example registers any @ServerEndpoint annotated beans with the underlying WebSocket container. When deployed to a standalone servlet container, this role is performed by a servlet container initializer, and the ServerEndpointExporter bean is not required.

74.17 Enable HTTP Response Compression

HTTP response compression is supported by Jetty, Tomcat, and Undertow. It can be enabled in application.properties , as follows:

server.compression.enabled=true

By default, responses must be at least 2048 bytes in length for compression to be performed. You can configure this behavior by setting the server.compression.min-response-size property.

By default, responses are compressed only if their content type is one of the following:

text/html
text/xml
text/plain
text/css

You can configure this behavior by setting the server.compression.mime-types property.

75. Spring MVC

Spring Boot has a number of starters that include Spring MVC. Note that some starters include a dependency on Spring MVC rather than include it directly. This section answers common questions about Spring MVC and Spring Boot.

75.1 Write a JSON REST Service

Any Spring @RestController in a Spring Boot application should render JSON response by default as long as Jackson2 is on the classpath, as shown in the following example:

@RestController
public class MyController {
	@RequestMapping("/thing")
	public MyThing thing() {
			return new MyThing();
}

As long as MyThing can be serialized by Jackson2 (true for a normal POJO or Groovy object), then localhost:8080/thing serves a JSON representation of it by default. Note that, in a browser, you might sometimes see XML responses, because browsers tend to send accept headers that prefer XML.

75.2 Write an XML REST Service

If you have the Jackson XML extension ( jackson-dataformat-xml ) on the classpath, you can use it to render XML responses. The previous example that we used for JSON would work. To use the Jackson XML renderer, add the following dependency to your project:

<dependency>
	<groupId>com.fasterxml.jackson.dataformat</groupId>
	<artifactId>jackson-dataformat-xml</artifactId>
</dependency>

You may also want to add a dependency on Woodstox. It is faster than the default StAX implementation provided by the JDK and also adds pretty-print support and improved namespace handling. The following listing shows how to include a dependency on Woodstox:

<dependency>
	<groupId>org.codehaus.woodstox</groupId>
	<artifactId>woodstox-core-asl</artifactId>
</dependency>

If Jackson’s XML extension is not available, JAXB (provided by default in the JDK) is used, with the additional requirement of having MyThing annotated as @XmlRootElement , as shown in the following example:

@XmlRootElement
public class MyThing {
	private String name;
	// .. getters and setters
}

To get the server to render XML instead of JSON, you might have to send an Accept: text/xml header (or use a browser).

75.3 Customize the Jackson ObjectMapper

Spring MVC (client and server side) uses HttpMessageConverters to negotiate content conversion in an HTTP exchange. If Jackson is on the classpath, you already get the default converter(s) provided by Jackson2ObjectMapperBuilder , an instance of which is auto-configured for you.

The ObjectMapper (or XmlMapper for Jackson XML converter) instance (created by default) has the following customized properties:

MapperFeature.DEFAULT_VIEW_INCLUSION is disabled
DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES is disabled

Spring Boot has also some features to make it easier to customize this behavior.

You can configure the ObjectMapper and XmlMapper instances by using the environment. Jackson provides an extensive suite of simple on/off features that can be used to configure various aspects of its processing. These features are described in six enums (in Jackson) that map onto properties in the environment:

Jackson enum	Environment property
`com.fasterxml.jackson.databind.DeserializationFeature`	`spring.jackson.deserialization.<feature_name>=true\|false`
`com.fasterxml.jackson.core.JsonGenerator.Feature`	`spring.jackson.generator.<feature_name>=true\|false`
`com.fasterxml.jackson.databind.MapperFeature`	`spring.jackson.mapper.<feature_name>=true\|false`
`com.fasterxml.jackson.core.JsonParser.Feature`	`spring.jackson.parser.<feature_name>=true\|false`
`com.fasterxml.jackson.databind.SerializationFeature`	`spring.jackson.serialization.<feature_name>=true\|false`
`com.fasterxml.jackson.annotation.JsonInclude.Include`	`spring.jackson.default-property-inclusion=always\|non_null\|non_absent\|non_default\|non_empty`

For example, to enable pretty print, set spring.jackson.serialization.indent_output=true . Note that, thanks to the use of relaxed binding , the case of indent_output does not have to match the case of the corresponding enum constant, which is INDENT_OUTPUT .

This environment-based configuration is applied to the auto-configured Jackson2ObjectMapperBuilder bean and applies to any mappers created by using the builder, including the auto-configured ObjectMapper bean.

The context’s Jackson2ObjectMapperBuilder can be customized by one or more Jackson2ObjectMapperBuilderCustomizer beans. Such customizer beans can be ordered (Boot’s own customizer has an order of 0), letting additional customization be applied both before and after Boot’s customization.

Any beans of type com.fasterxml.jackson.databind.Module are automatically registered with the auto-configured Jackson2ObjectMapperBuilder and are applied to any ObjectMapper instances that it creates. This provides a global mechanism for contributing custom modules when you add new features to your application.

If you want to replace the default ObjectMapper completely, either define a @Bean of that type and mark it as @Primary or, if you prefer the builder-based approach, define a Jackson2ObjectMapperBuilder @Bean . Note that, in either case, doing so disables all auto-configuration of the ObjectMapper .

If you provide any @Beans of type MappingJackson2HttpMessageConverter , they replace the default value in the MVC configuration. Also, a convenience bean of type HttpMessageConverters is provided (always available if you use the default MVC configuration). It has some useful methods to access the default and user-enhanced message converters.

See the “ Section 75.4, “Customize the @ResponseBody Rendering” ” section and the WebMvcAutoConfiguration source code for more details.

75.4 Customize the @ResponseBody Rendering

Spring uses HttpMessageConverters to render @ResponseBody (or responses from @RestController ). You can contribute additional converters by adding beans of the appropriate type in a Spring Boot context. If a bean you add is of a type that would have been included by default anyway (such as MappingJackson2HttpMessageConverter for JSON conversions), it replaces the default value. A convenience bean of type HttpMessageConverters is provided and is always available if you use the default MVC configuration. It has some useful methods to access the default and user-enhanced message converters (For example, it can be useful if you want to manually inject them into a custom RestTemplate ).

As in normal MVC usage, any WebMvcConfigurer beans that you provide can also contribute converters by overriding the configureMessageConverters method. However, unlike with normal MVC, you can supply only additional converters that you need (because Spring Boot uses the same mechanism to contribute its defaults). Finally, if you opt out of the Spring Boot default MVC configuration by providing your own @EnableWebMvc configuration, you can take control completely and do everything manually by using getMessageConverters from WebMvcConfigurationSupport .

See the WebMvcAutoConfiguration source code for more details.

75.5 Handling Multipart File Uploads

Spring Boot embraces the Servlet 3 javax.servlet.http.Part API to support uploading files. By default, Spring Boot configures Spring MVC with a maximum size of 1MB per file and a maximum of 10MB of file data in a single request. You may override these values, the location to which intermediate data is stored (for example, to the /tmp directory), and the threshold past which data is flushed to disk by using the properties exposed in the MultipartProperties class. For example, if you want to specify that files be unlimited, set the spring.servlet.multipart.max-file-size property to -1 .

The multipart support is helpful when you want to receive multipart encoded file data as a @RequestParam -annotated parameter of type MultipartFile in a Spring MVC controller handler method.

See the MultipartAutoConfiguration source for more details.

75.6 Switch Off the Spring MVC DispatcherServlet

Spring Boot wants to serve all content from the root of your application ( / ) down. If you would rather map your own servlet to that URL, you can do it. However, you may lose some of the other Boot MVC features. To add your own servlet and map it to the root resource, declare a @Bean of type Servlet and give it the special bean name, dispatcherServlet . (You can also create a bean of a different type with that name if you want to switch it off and not replace it.)

75.7 Switch off the Default MVC Configuration

The easiest way to take complete control over MVC configuration is to provide your own @Configuration with the @EnableWebMvc annotation. Doing so leaves all MVC configuration in your hands.

75.8 Customize ViewResolvers

A ViewResolver is a core component of Spring MVC, translating view names in @Controller to actual View implementations. Note that ViewResolvers are mainly used in UI applications, rather than REST-style services (a View is not used to render a @ResponseBody ). There are many implementations of ViewResolver to choose from, and Spring on its own is not opinionated about which ones you should use. Spring Boot, on the other hand, installs one or two for you, depending on what it finds on the classpath and in the application context. The DispatcherServlet uses all the resolvers it finds in the application context, trying each one in turn until it gets a result, so, if you add your own, you have to be aware of the order and in which position your resolver is added.

WebMvcAutoConfiguration adds the following ViewResolvers to your context:

An InternalResourceViewResolver named ‘defaultViewResolver’. This one locates physical resources that can be rendered by using the DefaultServlet (including static resources and JSP pages, if you use those). It applies a prefix and a suffix to the view name and then looks for a physical resource with that path in the servlet context (the defaults are both empty but are accessible for external configuration through spring.mvc.view.prefix and spring.mvc.view.suffix ). You can override it by providing a bean of the same type.
A BeanNameViewResolver named ‘beanNameViewResolver’. This is a useful member of the view resolver chain and picks up any beans with the same name as the View being resolved. It should not be necessary to override or replace it.
A ContentNegotiatingViewResolver named ‘viewResolver’ is added only if there are actually beans of type View present. This is a ‘master’ resolver, delegating to all the others and attempting to find a match to the ‘Accept’ HTTP header sent by the client. There is a useful blog about ContentNegotiatingViewResolver that you might like to study to learn more, and you might also look at the source code for detail. You can switch off the auto-configured ContentNegotiatingViewResolver by defining a bean named ‘viewResolver’.
If you use Thymeleaf, you also have a ThymeleafViewResolver named ‘thymeleafViewResolver’. It looks for resources by surrounding the view name with a prefix and suffix. The prefix is spring.thymeleaf.prefix , and the suffix is spring.thymeleaf.suffix . The values of the prefix and suffix default to ‘classpath:/templates/’ and ‘.html’, respectively. You can override ThymeleafViewResolver by providing a bean of the same name.
If you use FreeMarker, you also have a FreeMarkerViewResolver named ‘freeMarkerViewResolver’. It looks for resources in a loader path (which is externalized to spring.freemarker.templateLoaderPath and has a default value of ‘classpath:/templates/’) by surrounding the view name with a prefix and suffix. The prefix is externalized to spring.freemarker.prefix , and the suffix is externalized to spring.freemarker.suffix . The default values of the prefix and suffix are empty and ‘.ftl’, respectively. You can override FreeMarkerViewResolver by providing a bean of the same name.
If you use Groovy templates (actually, if groovy-templates is on your classpath), you also have a GroovyMarkupViewResolver named ‘groovyMarkupViewResolver’. It looks for resources in a loader path by surrounding the view name with a prefix and suffix (externalized to spring.groovy.template.prefix and spring.groovy.template.suffix ). The prefix and suffix have default values of ‘classpath:/templates/’ and ‘.tpl’, respectively. You can override GroovyMarkupViewResolver by providing a bean of the same name.

For more detail, see the following sections:

76. HTTP Clients

Spring Boot offers a number of starters that work with HTTP clients. This section answers questions related to doing so.

76.1 Configure RestTemplate to Use a Proxy

As described in Section 33.1, “RestTemplate Customization” , you can use a RestTemplateCustomizer with RestTemplateBuilder to build a customized RestTemplate . This is the recommended approach for creating a RestTemplate configured to use a proxy.

The exact details of the proxy configuration depend on the underlying client request factory that is being used. The following example configures HttpComponentsClientRequestFactory with an HttpClient that uses a proxy for all hosts except 192.168.0.5 :

static class ProxyCustomizer implements RestTemplateCustomizer {
	@Override
	public void customize(RestTemplate restTemplate) {
		HttpHost proxy = new HttpHost("proxy.example.com");
		HttpClient httpClient = HttpClientBuilder.create()
				.setRoutePlanner(new DefaultProxyRoutePlanner(proxy) {
					@Override
					public HttpHost determineProxy(HttpHost target,
							HttpRequest request, HttpContext context)
									throws HttpException {
						if (target.getHostName().equals("192.168.0.5")) {
							return null;
						return super.determineProxy(target, request, context);
				}).build();
		restTemplate.setRequestFactory(
				new HttpComponentsClientHttpRequestFactory(httpClient));
}

77. Logging

Spring Boot has no mandatory logging dependency, except for the Commons Logging API, of which there are many implementations to choose from. To use Logback , you need to include it and jcl-over-slf4j (which implements the Commons Logging API) on the classpath. The simplest way to do that is through the starters, which all depend on spring-boot-starter-logging . For a web application, you need only spring-boot-starter-web , since it depends transitively on the logging starter. If you use Maven, the following dependency adds logging for you:

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-web</artifactId>
</dependency>

Spring Boot has a LoggingSystem abstraction that attempts to configure logging based on the content of the classpath. If Logback is available, it is the first choice.

If the only change you need to make to logging is to set the levels of various loggers, you can do so in application.properties by using the "logging.level" prefix, as shown in the following example:

logging.level.org.springframework.web=DEBUG
logging.level.org.hibernate=ERROR

You can also set the location of a file to which to write the log (in addition to the console) by using "logging.file".

To configure the more fine-grained settings of a logging system, you need to use the native configuration format supported by the LoggingSystem in question. By default, Spring Boot picks up the native configuration from its default location for the system (such as classpath:logback.xml for Logback), but you can set the location of the config file by using the "logging.config" property.

77.1 Configure Logback for Logging

If you put a logback.xml in the root of your classpath, it is picked up from there (or from logback-spring.xml , to take advantage of the templating features provided by Boot). Spring Boot provides a default base configuration that you can include if you want to set levels, as shown in the following example:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
	<include resource="org/springframework/boot/logging/logback/base.xml"/>
	<logger name="org.springframework.web" level="DEBUG"/>
</configuration>

If you look at base.xml in the spring-boot jar, you can see that it uses some useful System properties that the LoggingSystem takes care of creating for you:

${PID} : The current process ID.
${LOG_FILE} : Whether logging.file was set in Boot’s external configuration.
${LOG_PATH} : Whether logging.path (representing a directory for log files to live in) was set in Boot’s external configuration.
${LOG_EXCEPTION_CONVERSION_WORD} : Whether logging.exception-conversion-word was set in Boot’s external configuration.

Spring Boot also provides some nice ANSI color terminal output on a console (but not in a log file) by using a custom Logback converter. See the default base.xml configuration for details.

If Groovy is on the classpath, you should be able to configure Logback with logback.groovy as well. If present, this setting is given preference.

77.1.1 Configure Logback for File-only Output

If you want to disable console logging and write output only to a file, you need a custom logback-spring.xml that imports file-appender.xml but not console-appender.xml , as shown in the following example:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
	<include resource="org/springframework/boot/logging/logback/defaults.xml" />
	<property name="LOG_FILE" value="${LOG_FILE:-${LOG_PATH:-${LOG_TEMP:-${java.io.tmpdir:-/tmp}}/}spring.log}"/>
	<include resource="org/springframework/boot/logging/logback/file-appender.xml" />
	<root level="INFO">
		<appender-ref ref="FILE" />
	</root>
</configuration>

You also need to add logging.file to your application.properties , as shown in the following example:

logging.file=myapplication.log

77.2 Configure Log4j for Logging

Spring Boot supports Log4j 2 for logging configuration if it is on the classpath. If you use the starters for assembling dependencies, you have to exclude Logback and then include log4j 2 instead. If you do not use the starters, you need to provide (at least) jcl-over-slf4j in addition to Log4j 2.

The simplest path is probably through the starters, even though it requires some jiggling with excludes. The following example shows how to set up the starters in Maven:

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter</artifactId>
	<exclusions>
		<exclusion>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-logging</artifactId>
		</exclusion>
	</exclusions>
</dependency>
<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-log4j2</artifactId>
</dependency>

	Note
	The Log4j starters gather together the dependencies for common logging requirements (such as having Tomcat use `java.util.logging` but configuring the output using Log4j 2). See the Actuator Log4j 2 samples for more detail and to see it in action.

77.2.1 Use YAML or JSON to Configure Log4j 2

In addition to its default XML configuration format, Log4j 2 also supports YAML and JSON configuration files. To configure Log4j 2 to use an alternative configuration file format, add the appropriate dependencies to the classpath and name your configuration files to match your chosen file format, as shown in the following example:

Format	Dependencies	File names
YAML	`com.fasterxml.jackson.core:jackson-databind` `com.fasterxml.jackson.dataformat:jackson-dataformat-yaml`	`log4j2.yaml` `log4j2.yml`
JSON	`com.fasterxml.jackson.core:jackson-databind`	`log4j2.json` `log4j2.jsn`

78. Data Access

Spring Boot includes a number of starters for working with data sources. This section answers questions related to doing so.

78.1 Configure a Custom DataSource

To configure your own DataSource , define a @Bean of that type in your configuration. Spring Boot reuses your DataSource anywhere one is required, including database initialization. If you need to externalize some settings, you can bind your DataSource to the environment (see “ Section 24.7.1, “Third-party Configuration” ”).

The following example shows how to define a data source in a bean:

@Bean
@ConfigurationProperties(prefix="app.datasource")
public DataSource dataSource() {
	return new FancyDataSource();
}

The following example shows how to define a data source by setting properties:

app.datasource.url=jdbc:h2:mem:mydb
app.datasource.username=sa
app.datasource.pool-size=30

Assuming that your FancyDataSource has regular JavaBean properties for the URL, the username, and the pool size, these settings are bound automatically before the DataSource is made available to other components. The regular database initialization also happens (so the relevant sub-set of spring.datasource.* can still be used with your custom configuration).

You can apply the same principle if you configure a custom JNDI DataSource , as shown in the following example:

@Bean(destroyMethod="")
@ConfigurationProperties(prefix="app.datasource")
public DataSource dataSource() throws Exception {
	JndiDataSourceLookup dataSourceLookup = new JndiDataSourceLookup();
	return dataSourceLookup.getDataSource("java:comp/env/jdbc/YourDS");
}

Spring Boot also provides a utility builder class, called DataSourceBuilder , that can be used to create one of the standard data sources (if it is on the classpath). The builder can detect the one to use based on what’s available on the classpath. It also auto-detects the driver based on the JDBC URL.

The following example shows how to create a data source by using a DataSourceBuilder :

@Bean
@ConfigurationProperties("app.datasource")
public DataSource dataSource() {
	return DataSourceBuilder.create().build();
}

To run an app with that DataSource , all you need is the connection information. Pool-specific settings can also be provided. Check the implementation that is going to be used at runtime for more details.

The following example shows how to define a JDBC data source by setting properties:

app.datasource.url=jdbc:mysql://localhost/test
app.datasource.username=dbuser
app.datasource.password=dbpass
app.datasource.pool-size=30

However, there is a catch. Because the actual type of the connection pool is not exposed, no keys are generated in the metadata for your custom DataSource and no completion is available in your IDE (because the DataSource interface exposes no properties). Also, if you happen to have Hikari on the classpath, this basic setup does not work, because Hikari has no url property (but does have a jdbcUrl property). In that case, you must rewrite your configuration as follows:

app.datasource.jdbc-url=jdbc:mysql://localhost/test
app.datasource.username=dbuser
app.datasource.password=dbpass
app.datasource.maximum-pool-size=30

You can fix that by forcing the connection pool to use and return a dedicated implementation rather than DataSource . You cannot change the implementation at runtime, but the list of options will be explicit.

The following example shows how create a HikariDataSource with DataSourceBuilder :

@Bean
@ConfigurationProperties("app.datasource")
public HikariDataSource dataSource() {
	return DataSourceBuilder.create().type(HikariDataSource.class).build();
}

You can even go further by leveraging what DataSourceProperties does for you — that is, by providing a default embedded database with a sensible username and password if no URL is provided. You can easily initialize a DataSourceBuilder from the state of any DataSourceProperties object, so you could also inject the one Spring Boot creates automatically. However, that would split your configuration into two namespaces: url , username , password , type , and driver on spring.datasource and the rest on your custom namespace ( app.datasource ). To avoid that, you can redefine a custom DataSourceProperties on your custom namespace, as shown in the following example:

@Bean
@Primary
@ConfigurationProperties("app.datasource")
public DataSourceProperties dataSourceProperties() {
	return new DataSourceProperties();
@Bean
@ConfigurationProperties("app.datasource")
public HikariDataSource dataSource(DataSourceProperties properties) {
	return properties.initializeDataSourceBuilder().type(HikariDataSource.class)
			.build();
}

This setup puts you in sync with what Spring Boot does for you by default, except that a dedicated connection pool is chosen (in code) and its settings are exposed in the same namespace. Because DataSourceProperties is taking care of the url / jdbcUrl translation for you, you can configure it as follows:

app.datasource.url=jdbc:mysql://localhost/test
app.datasource.username=dbuser
app.datasource.password=dbpass
app.datasource.maximum-pool-size=30

	Note
	Because your custom configuration chooses to go with Hikari, `app.datasource.type` has no effect. In practice, the builder is initialized with whatever value you might set there and then overridden by the call to `.type()` .

See “ Section 29.1, “Configure a DataSource” ” in the ‘Spring Boot features’ section and the DataSourceAutoConfiguration class for more details.

78.2 Configure Two DataSources

If you need to configure multiple data sources, you can apply the same tricks that are described in the previous section. You must, however, mark one of the DataSource instances as @Primary , because various auto-configurations down the road expect to be able to get one by type.

If you create your own DataSource , the auto-configuration backs off. In the following example, we provide the exact same feature set as the auto-configuration provides on the primary data source:

@Bean
@Primary
@ConfigurationProperties("app.datasource.foo")
public DataSourceProperties fooDataSourceProperties() {
	return new DataSourceProperties();
@Bean
@Primary
@ConfigurationProperties("app.datasource.foo")
public DataSource fooDataSource() {
	return fooDataSourceProperties().initializeDataSourceBuilder().build();
@Bean
@ConfigurationProperties("app.datasource.bar")
public BasicDataSource barDataSource() {
	return DataSourceBuilder.create().type(BasicDataSource.class).build();
}

	Tip
	`fooDataSourceProperties` has to be flagged as `@Primary` so that the database initializer feature uses your copy (if you use the initializer).

Both data sources are also bound for advanced customizations. For instance, you could configure them as follows:

app.datasource.foo.type=com.zaxxer.hikari.HikariDataSource
app.datasource.foo.maximum-pool-size=30
app.datasource.bar.url=jdbc:mysql://localhost/test
app.datasource.bar.username=dbuser
app.datasource.bar.password=dbpass
app.datasource.bar.max-total=30

You can apply the same concept to the secondary DataSource as well, as shown in the following example:

@Bean
@Primary
@ConfigurationProperties("app.datasource.foo")
public DataSourceProperties fooDataSourceProperties() {
	return new DataSourceProperties();
@Bean
@Primary
@ConfigurationProperties("app.datasource.foo")
public DataSource fooDataSource() {
	return fooDataSourceProperties().initializeDataSourceBuilder().build();
@Bean
@ConfigurationProperties("app.datasource.bar")
public DataSourceProperties barDataSourceProperties() {
	return new DataSourceProperties();
@Bean
@ConfigurationProperties("app.datasource.bar")
public DataSource barDataSource() {
	return barDataSourceProperties().initializeDataSourceBuilder().build();
}

The preceding example configures two data sources on custom namespaces with the same logic as Spring Boot would use in auto-configuration.

78.3 Use Spring Data Repositories

Spring Data can create implementations for you of @Repository interfaces of various flavors. Spring Boot handles all of that for you, as long as those @Repositories are included in the same package (or a sub-package) of your @EnableAutoConfiguration class.

For many applications, all you need is to put the right Spring Data dependencies on your classpath (there is a spring-boot-starter-data-jpa for JPA and a spring-boot-starter-data-mongodb for Mongodb) and create some repository interfaces to handle your @Entity objects. Examples are in the JPA sample and the Mongodb sample .

Spring Boot tries to guess the location of your @Repository definitions, based on the @EnableAutoConfiguration it finds. To get more control, use the @EnableJpaRepositories annotation (from Spring Data JPA).

78.4 Separate @Entity Definitions from Spring Configuration

Spring Boot tries to guess the location of your @Entity definitions, based on the @EnableAutoConfiguration it finds. To get more control, you can use the @EntityScan annotation, as shown in the following example:

@Configuration
@EnableAutoConfiguration
@EntityScan(basePackageClasses=City.class)
public class Application {
	//...
}

78.5 Configure JPA Properties

Spring Data JPA already provides some vendor-independent configuration options (such as those for SQL logging), and Spring Boot exposes those options and a few more for Hibernate as external configuration properties. Some of them are automatically detected according to the context so you should not have to set them.

The spring.jpa.hibernate.ddl-auto is a special case, because, depending on runtime conditions, it has different defaults. If an embedded database is used and no schema manager (such as Liquibase or Flyway) is handling the DataSource , it defaults to create-drop . In all other cases, it defaults to none .

The dialect to use is also automatically detected based on the current DataSource , but you can set spring.jpa.database yourself if you want to be explicit and bypass that check on startup.

	Note
	Specifying a `database` leads to the configuration of a well-defined Hibernate dialect. Several databases have more than one `Dialect` , and this may not suit your need. In that case, you can either set `spring.jpa.database` to `default` to let Hibernate figure things out or set the dialect by setting the `spring.jpa.database-platform` property.

The most common options to set are shown in the following example:

spring.jpa.hibernate.naming.physical-strategy=com.example.MyPhysicalNamingStrategy
spring.jpa.show-sql=true

In addition, all properties in spring.jpa.properties.* are passed through as normal JPA properties (with the prefix stripped) when the local EntityManagerFactory is created.

78.6 Configure Hibernate Naming Strategy

Hibernate uses two different naming strategies to map names from the object model to the corresponding database names. The fully qualified class name of the physical and the implicit strategy implementations can be configured by setting the spring.jpa.hibernate.naming.physical-strategy and spring.jpa.hibernate.naming.implicit-strategy properties, respectively. Alternatively, if ImplicitNamingStrategy or PhysicalNamingStrategy beans are available in the application context, Hibernate will be automatically configured to use them.

By default, Spring Boot configures the physical naming strategy with SpringPhysicalNamingStrategy . This implementation provides the same table structure as Hibernate 4: all dots are replaced by underscores and camel casing is replaced by underscores as well. By default, all table names are generated in lower case, but it is possible to override that flag if your schema requires it.

For example, a TelephoneNumber entity is mapped to the telephone_number table.

If you prefer to use Hibernate 5’s default instead, set the following property:

spring.jpa.hibernate.naming.physical-strategy=org.hibernate.boot.model.naming.PhysicalNamingStrategyStandardImpl

Alternatively, configure the following bean:

@Bean
public PhysicalNamingStrategy physicalNamingStrategy() {
	return new PhysicalNamingStrategyStandardImpl();
}

See HibernateJpaAutoConfiguration and JpaBaseConfiguration for more details.

78.7 Use a Custom EntityManagerFactory

To take full control of the configuration of the EntityManagerFactory , you need to add a @Bean named ‘entityManagerFactory’. Spring Boot auto-configuration switches off its entity manager in the presence of a bean of that type.

78.8 Use Two EntityManagers

Even if the default EntityManagerFactory works fine, you need to define a new one. Otherwise, the presence of the second bean of that type switches off the default. To make it easy to do, you can use the convenient EntityManagerBuilder provided by Spring Boot. Alternatively, you can just the LocalContainerEntityManagerFactoryBean directly from Spring ORM, as shown in the following example:

// add two data sources configured as above
@Bean
public LocalContainerEntityManagerFactoryBean customerEntityManagerFactory(
		EntityManagerFactoryBuilder builder) {
	return builder
			.dataSource(customerDataSource())
			.packages(Customer.class)
			.persistenceUnit("customers")
			.build();
@Bean
public LocalContainerEntityManagerFactoryBean orderEntityManagerFactory(
		EntityManagerFactoryBuilder builder) {
	return builder
			.dataSource(orderDataSource())
			.packages(Order.class)
			.persistenceUnit("orders")
			.build();
}

The configuration above almost works on its own. To complete the picture, you need to configure TransactionManagers for the two EntityManagers as well. One of them could be picked up by the default JpaTransactionManager in Spring Boot if you mark it as @Primary . The other would have to be explicitly injected into a new instance. Alternatively, you might be able to use a JTA transaction manager that spans both.

If you are using Spring Data, you need to configure @EnableJpaRepositories accordingly, as shown in the following example:

@Configuration
@EnableJpaRepositories(basePackageClasses = Customer.class,
		entityManagerFactoryRef = "customerEntityManagerFactory")
public class CustomerConfiguration {
@Configuration
@EnableJpaRepositories(basePackageClasses = Order.class,
		entityManagerFactoryRef = "orderEntityManagerFactory")
public class OrderConfiguration {
}

78.9 Use a Traditional `persistence.xml` File

Spring does not require the use of XML to configure the JPA provider, and Spring Boot assumes you want to take advantage of that feature. If you prefer to use persistence.xml , you need to define your own @Bean of type LocalEntityManagerFactoryBean (with an ID of ‘entityManagerFactory’) and set the persistence unit name there.

See JpaBaseConfiguration for the default settings.

78.10 Use Spring Data JPA and Mongo Repositories

Spring Data JPA and Spring Data Mongo can both automatically create Repository implementations for you. If they are both present on the classpath, you might have to do some extra configuration to tell Spring Boot which one (or both) you want to create repositories for you. The most explicit way to do that is to use the standard Spring Data @EnableJpaRepositories and @EnableMongoRepositories annotations and provide the location of your Repository interfaces.

There are also flags ( spring.data.*.repositories.enabled and spring.data.*.repositories.type ) that you can use to switch the auto-configured repositories on and off in external configuration. Doing so is useful, for instance, in case you want to switch off the Mongo repositories and still use the auto-configured MongoTemplate .

The same obstacle and the same features exist for other auto-configured Spring Data repository types (Elasticsearch, Solr, and others). To work with them, change the names of the annotations and flags accordingly.

78.11 Expose Spring Data Repositories as REST Endpoint

Spring Data REST can expose the Repository implementations as REST endpoints for you, provided Spring MVC has been enabled for the application.

Spring Boot exposes a set of useful properties (from the spring.data.rest namespace) that customize the RepositoryRestConfiguration . If you need to provide additional customization, you should use a RepositoryRestConfigurer bean.

	Note
	If you do not specify any order on your custom `RepositoryRestConfigurer` , it runs after the one Spring Boot uses internally. If you need to specify an order, make sure it is higher than 0.

78.12 Configure a Component that is Used by JPA

If you want to configure a component that JPA uses, then you need to ensure that the component is initialized before JPA. When the component is auto-configured, Spring Boot takes care of this for you. For example, when Flyway is auto-configured, Hibernate is configured to depend upon Flyway so that Flyway has a chance to initialize the database before Hibernate tries to use it.

If you are configuring a component yourself, you can use an EntityManagerFactoryDependsOnPostProcessor subclass as a convenient way of setting up the necessary dependencies. For example, if you use Hibernate Search with Elasticsearch as its index manager, any EntityManagerFactory beans must be configured to depend on the elasticsearchClient bean, as shown in the following example:

/**
 * {@link EntityManagerFactoryDependsOnPostProcessor} that ensures that
 * {@link EntityManagerFactory} beans depend on the {@code elasticsearchClient} bean.
@Configuration
static class ElasticsearchJpaDependencyConfiguration
		extends EntityManagerFactoryDependsOnPostProcessor {
	ElasticsearchJpaDependencyConfiguration() {
		super("elasticsearchClient");
}

79. Database Initialization

An SQL database can be initialized in different ways depending on what your stack is. Of course, you can also do it manually, provided the database is a separate process.

79.1 Initialize a Database Using JPA

JPA has features for DDL generation, and these can be set up to run on startup against the database. This is controlled through two external properties:

spring.jpa.generate-ddl (boolean) switches the feature on and off and is vendor independent.
spring.jpa.hibernate.ddl-auto (enum) is a Hibernate feature that controls the behavior in a more fine-grained way. This feature is described in more detail later in the document.

79.2 Initialize a Database Using Hibernate

You can set spring.jpa.hibernate.ddl-auto explicitly and the standard Hibernate property values are none , validate , update , create , and create-drop . Spring Boot chooses a default value for you based on whether it thinks your database is embedded. It defaults to create-drop if no schema manager has been detected or none in all other cases. An embedded database is detected by looking at the Connection type. hsqldb , h2 , and derby are embedded, and others are not. Be careful when switching from in-memory to a ‘real’ database that you do not make assumptions about the existence of the tables and data in the new platform. You either have to set ddl-auto explicitly or use one of the other mechanisms to initialize the database.

	Note
	You can output the schema creation by enabling the `org.hibernate.SQL` logger. This is done for you automatically if you enable the debug mode .

In addition, a file named import.sql in the root of the classpath is executed on startup if Hibernate creates the schema from scratch (that is, if the ddl-auto property is set to create or create-drop ). This can be useful for demos and for testing if you are careful but is probably not something you want to be on the classpath in production. It is a Hibernate feature (and has nothing to do with Spring).

79.3 Initialize a Database

Spring Boot can automatically create the schema (DDL scripts) of your DataSource and initialize it (DML scripts). It loads SQL from the standard root classpath locations: schema.sql and data.sql , respectively. In addition, Spring Boot processes the schema-${platform}.sql and data-${platform}.sql files (if present), where platform is the value of spring.datasource.platform . This allows you to switch to database-specific scripts if necessary. For example, you might choose to set it to the vendor name of the database ( hsqldb , h2 , oracle , mysql , postgresql , and so on).

Spring Boot automatically creates the schema of an embedded DataSource . This behavior can be customized by using the spring.datasource.initialization-mode property (and it can also be always or never ).

By default, Spring Boot enables the fail-fast feature of the Spring JDBC initializer, so, if the scripts cause exceptions, the application fails to start. You can tune that behavior by setting spring.datasource.continue-on-error .

	Note
	In a JPA-based app, you can choose to let Hibernate create the schema or use `schema.sql` , but you cannot do both. Make sure to disable `spring.jpa.hibernate.ddl-auto` if you use `schema.sql` .

79.4 Initialize a Spring Batch Database

If you use Spring Batch, it comes pre-packaged with SQL initialization scripts for most popular database platforms. Spring Boot can detect your database type and execute those scripts on startup. If you use an embedded database, this happens by default. You can also enable it for any database type, as shown in the following example:

spring.batch.initialize-schema=always

You can also switch off the initialization explicitly by setting spring.batch.initialize-schema=never .

79.5 Use a Higher-level Database Migration Tool

Spring Boot supports two higher-level migration tools: Flyway and Liquibase .

79.5.1 Execute Flyway Database Migrations on Startup

To automatically run Flyway database migrations on startup, add the org.flywaydb:flyway-core to your classpath.

The migrations are scripts in the form V<VERSION>__<NAME>.sql (with <VERSION> an underscore-separated version, such as ‘1’ or ‘2_1’). By default, they live in a folder called classpath:db/migration , but you can modify that location by setting spring.flyway.locations . You can also add a special {vendor} placeholder to use vendor-specific scripts. Assume the following:

spring.flyway.locations=db/migration/{vendor}

Rather than using db/migration , the preceding configuration sets the folder to use according to the type of the database (such as db/migration/mysql for MySQL). The list of supported database are available in DatabaseDriver .

See the Flyway class from flyway-core for details of available settings such as schemas and others. In addition, Spring Boot provides a small set of properties (in FlywayProperties ) that can be used to disable the migrations or switch off the location checking. Spring Boot calls Flyway.migrate() to perform the database migration. If you would like more control, provide a @Bean that implements FlywayMigrationStrategy .

Flyway supports SQL and Java callbacks . To use SQL-based callbacks, place the callback scripts in the classpath:db/migration folder. To use Java-based callbacks, create one or more beans that implement FlywayCallback or, preferably, extend BaseFlywayCallback . Any such beans are automatically registered with Flyway . They can be ordered by using @Order or by implementing Ordered .

By default, Flyway autowires the ( @Primary ) DataSource in your context and uses that for migrations. If you like to use a different DataSource , you can create one and mark its @Bean as @FlywayDataSource . If you do so and want two data sources, remember to create another one and mark it as @Primary . Alternatively, you can use Flyway’s native DataSource by setting spring.flyway.[url,user,password] in external properties.

There is a Flyway sample so that you can see how to set things up.

You can also use Flyway to provide data for specific scenarios. For example, you can place test-specific migrations in src/test/resources and they are run only when your application starts for testing. If you want to be more sophisticated, you can use profile-specific configuration to customize spring.flyway.locations so that certain migrations run only when a particular profile is active. For example, in application-dev.properties , you might specify the following setting:

spring.flyway.locations=classpath:/db/migration,classpath:/dev/db/migration

With that setup, migrations in dev/db/migration run only when the dev profile is active.

79.5.2 Execute Liquibase Database Migrations on Startup

To automatically run Liquibase database migrations on startup, add the org.liquibase:liquibase-core to your classpath.

By default, the master change log is read from db/changelog/db.changelog-master.yaml , but you can change the location by setting spring.liquibase.change-log . In addition to YAML, Liquibase also supports JSON, XML, and SQL change log formats.

By default, Liquibase autowires the ( @Primary ) DataSource in your context and uses that for migrations. If you like to use a different DataSource , you can create one and mark its @Bean as @LiquibaseDataSource . If you do so and you want two data sources, remember to create another one and mark it as @Primary . Alternatively, you can use Liquibase’s native DataSource by setting spring.liquibase.[url,user,password] in external properties.

See LiquibaseProperties for details about available settings such as contexts, the default schema, and others.

There is a Liquibase sample so that you can see how to set things up.

80. Messaging

Spring Boot offers a number of starters that include messaging. This section answers questions that arise from using messaging with Spring Boot.

80.1 Disable Transacted JMS Session

If your JMS broker does not support transacted session, you have to disable the support of transactions altogether. If you create your own JmsListenerContainerFactory , there is nothing to do, since, by default it cannot be transacted. If you want to use the DefaultJmsListenerContainerFactoryConfigurer to reuse Spring Boot’s default, you can disable transacted session, as follows:

@Bean
public DefaultJmsListenerContainerFactory jmsListenerContainerFactory(
		ConnectionFactory connectionFactory,
		DefaultJmsListenerContainerFactoryConfigurer configurer) {
	DefaultJmsListenerContainerFactory listenerFactory =
			new DefaultJmsListenerContainerFactory();
	configurer.configure(listenerFactory, connectionFactory);
	listenerFactory.setTransactionManager(null);
	listenerFactory.setSessionTransacted(false);
	return listenerFactory;
}

The preceding example overrides the default factory, and it should be applied to any other factory that your application defines, if any.

81. Batch Applications

	Note
	By default, batch applications require a `DataSource` to store job details. If you want to deviate from that, you need to implement `BatchConfigurer` . See Javadoc of `@EnableBatchProcessing` for more details.

81.1 Execute Spring Batch Jobs on Startup

Spring Batch auto-configuration is enabled by adding @EnableBatchProcessing (from Spring Batch) somewhere in your context.

By default, it executes all Jobs in the application context on startup (see JobLauncherCommandLineRunner for details). You can narrow down to a specific job or jobs by specifying spring.batch.job.names (comma-separated job name patterns).

If the application context includes a JobRegistry , the jobs in spring.batch.job.names are looked up in the registry instead of being autowired from the context. This is a common pattern with more complex systems, where multiple jobs are defined in child contexts and registered centrally.

See BatchAutoConfiguration @EnableBatchProcessing for more details.

82. Actuator

Spring Boot includes the Spring Boot Actuator. This section answers questions that often arise from its use.

82.1 Change the HTTP Port or Address of the Actuator Endpoints

In a standalone application, the Actuator HTTP port defaults to the same as the main HTTP port. To make the application listen on a different port, set the external property, management.server.port . To listen on a completely different network address (such as when you have an internal network for management and an external one for user applications), you can also set management.server.address to a valid IP address to which the server is able to bind.

For more detail, see the ManagementServerProperties source code and “ Section 50.2, “Customizing the Management Server Port” ” in the ‘Production-ready features’ section.

82.2 Customize the ‘whitelabel’ Error Page

Spring Boot installs a ‘whitelabel’ error page that you see in a browser client if you encounter a server error (machine clients consuming JSON and other media types should see a sensible response with the right error code).

	Note
	Set `server.error.whitelabel.enabled=false` to switch the default error page off. Doing so restores the default of the servlet container that you are using. Note that Spring Boot still tries to resolve the error view, so you should probably add you own error page rather than disabling it completely.

Overriding the error page with your own depends on the templating technology that you use. For example, if you use Thymeleaf, you can add an error.html template. If you use FreeMarker, you can add an error.ftl template. In general, you need a View that resolves with a name of error or a @Controller that handles the /error path. Unless you replaced some of the default configuration, you should find a BeanNameViewResolver in your ApplicationContext , so a @Bean named error would be a simple way of doing that. See ErrorMvcAutoConfiguration for more options.

See also the section on “ Error Handling ” for details of how to register handlers in the servlet container.

83. Security

83.1 Switch off the Spring Boot Security Configuration

If you define a @Configuration with @EnableWebSecurity anywhere in your application, it switches off the default webapp security settings in Spring Boot (but leaves the Actuator’s security enabled). To tweak the defaults try setting properties in security.* (see SecurityProperties for details of available settings) and the SECURITY section of “ Common Application Properties ”.

83.2 Change the AuthenticationManager and Add User Accounts

If you provide a @Bean of type AuthenticationManager , the default one is not created, so you have the full feature set of Spring Security available (such as various authentication options ).

Spring Security also provides a convenient AuthenticationManagerBuilder , which can be used to build an AuthenticationManager with common options. The recommended way to use this in a webapp is to inject it into a void method in a WebSecurityConfigurerAdapter , as shown in the following example:

@Configuration
public class SecurityConfiguration extends WebSecurityConfigurerAdapter {
	@Autowired
	public void configureGlobal(AuthenticationManagerBuilder auth) throws Exception {
			auth.inMemoryAuthentication()
				.withUser("barry").password("password").roles("USER"); // ... etc.
	// ... other stuff for application security
}

You get the best results if you put this in a nested class or a standalone class (that is, not mixed in with a lot of other @Beans that might be allowed to influence the order of instantiation). The secure web sample is a useful template to follow.

If you experience instantiation issues (for example, when using JDBC or JPA for the user detail store), it might be worth extracting the AuthenticationManagerBuilder callback into a GlobalAuthenticationConfigurerAdapter (in the init() method so that it happens before the authentication manager is needed elsewhere), as shown in the following example:

@Configuration
public class AuthenticationManagerConfiguration extends
		GlobalAuthenticationConfigurerAdapter {
	@Override
	public void init(AuthenticationManagerBuilder auth) {
		auth.inMemoryAuthentication() // ... etc.
}

83.3 Enable HTTPS When Running behind a Proxy Server

Ensuring that all your main endpoints are only available over HTTPS is an important chore for any application. If you use Tomcat as a servlet container, then Spring Boot adds Tomcat’s own RemoteIpValve automatically if it detects some environment settings, and you should be able to rely on the HttpServletRequest to report whether it is secure or not (even downstream of a proxy server that handles the real SSL termination). The standard behavior is determined by the presence or absence of certain request headers ( x-forwarded-for and x-forwarded-proto ), whose names are conventional, so it should work with most front-end proxies. You can switch on the valve by adding some entries to application.properties , as shown in the following example:

server.tomcat.remote-ip-header=x-forwarded-for
server.tomcat.protocol-header=x-forwarded-proto

(The presence of either of those properties switches on the valve. Alternatively, you can add the RemoteIpValve yourself by adding a TomcatServletWebServerFactory bean.)

Spring Security can also be configured to require a secure channel for all (or some) requests. To switch that on in a Spring Boot application, set security.require_ssl to true in application.properties .

84. Hot Swapping

Spring Boot supports hot swapping. This section answers questions about how it works.

84.1 Reload Static Content

There are several options for hot reloading. The recommended approach is to use spring-boot-devtools , as it provides additional development-time features, such as support for fast application restarts and LiveReload as well as sensible development-time configuration (such as template caching). Devtools works by monitoring the classpath for changes. This means that static resource changes must be "built" for the change to take affect. By default, this happens automatically in Eclipse when you save your changes. In IntelliJ IDEA, Make Project triggers the necessary build. Due to the default restart exclusions , changes to static resources do not trigger a restart of your application. They do, however, trigger a live reload.

Alternatively, running in an IDE (especially with debugging on) is a good way to do development (all modern IDEs allow reloading of static resources and usually also hot-swapping of Java class changes).

Finally, the Maven and Gradle plugins can be configured (see the addResources property) to support running from the command line with reloading of static files directly from source. You can use that with an external css/js compiler process if you are writing that code with higher-level tools.

84.2 Reload Templates without Restarting the Container

Most of the templating technologies supported by Spring Boot include a configuration option to disable caching (described later in this document). If you use the spring-boot-devtools module, these properties are automatically configured for you at development time.

84.2.1 Thymeleaf Templates

If you use Thymeleaf, set spring.thymeleaf.cache to false . See ThymeleafAutoConfiguration for other Thymeleaf customization options.

84.2.2 FreeMarker Templates

If you use FreeMarker, set spring.freemarker.cache to false . See FreeMarkerAutoConfiguration for other FreeMarker customization options.

84.2.3 Groovy Templates

If you use Groovy templates, set spring.groovy.template.cache to false . See GroovyTemplateAutoConfiguration for other Groovy customization options.

84.3 Fast Application Restarts

The spring-boot-devtools module includes support for automatic application restarts. While not as fast as technologies such as JRebel it is usually significantly faster than a “cold start”. You should probably give it a try before investigating some of the more complex reload options discussed later in this document.

For more details, see the Chapter 20, Developer Tools section.

84.4 Reload Java Classes without Restarting the Container

Many modern IDEs (Eclipse, IDEA, and others) support hot swapping of bytecode, so, if you make a change that does not affect class or method signatures, it should reload cleanly with no side effects.

85. Build

Spring Boot includes build plugins for Maven and Gradle. This section answers common questions about these plugins.

85.1 Generate Build Information

Both the Maven plugin and the Gradle plugin allow generating build information containing the coordinates, name, and version of the project. The plugins can also be configured to add additional properties through configuration. When such a file is present, Spring Boot auto-configures a BuildProperties bean.

To generate build information with Maven, add an execution for the build-info goal, as shown in the following example:

<build>
	<plugins>
		<plugin>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-maven-plugin</artifactId>
			<version>2.0.0.M7</version>
			<executions>
				<execution>
					<goals>
						<goal>build-info</goal>
					</goals>
				</execution>
			</executions>
		</plugin>
	</plugins>
</build>

	Tip
	See the Spring Boot Maven Plugin documentation for more details.

The following example does the same with Gradle:

springBoot {
	buildInfo()
}

Additional properties can be added by using the DSL, as shown in the following example:

springBoot  {
	buildInfo {
		additionalProperties = [
			'foo': 'bar'
}

85.2 Generate Git Information

Both Maven and Gradle allow generating a git.properties file containing information about the state of your git source code repository when the project was built.

For Maven users, the spring-boot-starter-parent POM includes a pre-configured plugin to generate a git.properties file. To use it, add the following declaration to your POM:

<build>
	<plugins>
		<plugin>
			<groupId>pl.project13.maven</groupId>
			<artifactId>git-commit-id-plugin</artifactId>
		</plugin>
	</plugins>
</build>

Gradle users can achieve the same result by using the gradle-git-properties plugin, as shown in the following example:

plugins {
	id "com.gorylenko.gradle-git-properties" version "1.4.17"
}

	Tip
	The commit time in `git.properties` is expected to match the following format: `yyyy-MM-dd’T’HH:mm:ssZ` . This is the default format for both plugins listed above. Using this format allows the time to be parsed into a `Date` and its format, when serialized to JSON, to be controlled by Jackson’s date serialization configuration settings.

85.3 Customize Dependency Versions

If you use a Maven build that inherits directly or indirectly from spring-boot-dependencies (for instance spring-boot-starter-parent ) but you want to override a specific third-party dependency, you can add appropriate <properties> elements. Browse the spring-boot-dependencies POM for a complete list of properties. For example, to pick a different slf4j version you would add the following property:

<properties>
	<slf4j.version>1.7.5<slf4j.version>
</properties>

	Note
	Doing so only works if your Maven project inherits (directly or indirectly) from `spring-boot-dependencies` . If you have added `spring-boot-dependencies` in your own `dependencyManagement` section with `<scope>import</scope>` , you have to redefine the artifact yourself instead of overriding the property.

	Warning
	Each Spring Boot release is designed and tested against a specific set of third-party dependencies. Overriding versions may cause compatibility issues.

85.4 Create an Executable JAR with Maven

The spring-boot-maven-plugin can be used to create an executable ‘fat’ JAR. If you are using the spring-boot-starter-parent POM, you can simply declare the plugin and your jars are repackaged as follows:

<build>
	<plugins>
		<plugin>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-maven-plugin</artifactId>
		</plugin>
	</plugins>
</build>

If you do not use the parent POM, you can still use the plugin. However, you must additionally add an <executions> section, as follows:

<build>
	<plugins>
		<plugin>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-maven-plugin</artifactId>
			<version>2.0.0.M7</version>
			<executions>
				<execution>
					<goals>
						<goal>repackage</goal>
					</goals>
				</execution>
			</executions>
		</plugin>
	</plugins>
</build>

See the plugin documentation for full usage details.

85.5 Use a Spring Boot Application as a Dependency

Like a war file, a Spring Boot application is not intended to be used as a dependency. If your application contains classes that you want to share with other projects, the recommended approach is to move that code into a separate module. The separate module can then be depended upon by your application and other projects.

If you cannot rearrange your code as recommended above, Spring Boot’s Maven and Gradle plugins must be configured to produce a separate artifact that is suitable for use as a dependency. The executable archive cannot be used as a dependency as the executable jar format packages application classes in BOOT-INF/classes . This means that they cannot be found when the executable jar is used as a dependency.

To produce the two artifacts, one that can be used as a dependency and one that is executable, a classifier must be specified. This classifier is applied to the name of the executable archive, leaving the default archive for use as a dependency.

To configure a classifier of exec in Maven, the following configuration can be used:

<build>
	<plugins>
		<plugin>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-maven-plugin</artifactId>
			<configuration>
				<classifier>exec</classifier>
			</configuration>
		</plugin>
	</plugins>
</build>

85.6 Extract Specific Libraries When an Executable Jar Runs

Most nested libraries in an executable jar do not need to be unpacked in order to run. However, certain libraries can have problems. For example, JRuby includes its own nested jar support, which assumes that the jruby-complete.jar is always directly available as a file in its own right.

To deal with any problematic libraries, you can flag that specific nested jars should be automatically unpacked to the ‘temp folder’ when the executable jar first runs.

For example, to indicate that JRuby should be flagged for unpacking by using the Maven Plugin, you would add the following configuration:

<build>
	<plugins>
		<plugin>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-maven-plugin</artifactId>
			<configuration>
				<requiresUnpack>
					<dependency>
						<groupId>org.jruby</groupId>
						<artifactId>jruby-complete</artifactId>
					</dependency>
				</requiresUnpack>
			</configuration>
		</plugin>
	</plugins>
</build>

85.7 Create a Non-executable JAR with Exclusions

Often, if you have an executable and a non-executable jar as build products, the executable version has additional configuration files that are not needed in a library jar. For example, the application.yml configuration file might by excluded from the non-executable JAR.

In Maven, the executable jar must be the main artifact and you can add a classified jar for the library, as follows:

<build>
	<plugins>
		<plugin>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-maven-plugin</artifactId>
		</plugin>
		<plugin>
			<artifactId>maven-jar-plugin</artifactId>
			<executions>
				<execution>
					<id>lib</id>
					<phase>package</phase>
					<goals>
						<goal>jar</goal>
					</goals>
					<configuration>
						<classifier>lib</classifier>
						<excludes>
							<exclude>application.yml</exclude>
						</excludes>
					</configuration>
				</execution>
			</executions>
		</plugin>
	</plugins>
</build>

85.8 Remote Debug a Spring Boot Application Started with Maven

To attach a remote debugger to a Spring Boot application that was started with Maven, you can use the jvmArguments property of the maven plugin .

See this example for more details.

85.9 Build an Executable Archive from Ant without Using `spring-boot-antlib`

To build with Ant, you need to grab dependencies, compile, and then create a jar or war archive. To make it executable, you can either use the spring-boot-antlib module or you can follow these instructions:

If you are building a jar, package the application’s classes and resources in a nested BOOT-INF/classes directory. If you are building a war, package the application’s classes in a nested WEB-INF/classes directory as usual.
Add the runtime dependencies in a nested BOOT-INF/lib directory for a jar or WEB-INF/lib for a war. Remember not to compress the entries in the archive.
Add the provided (embedded container) dependencies in a nested BOOT-INF/lib directory for a jar or WEB-INF/lib-provided for a war. Remember not to compress the entries in the archive.
Add the spring-boot-loader classes at the root of the archive (so that the Main-Class is available).
Use the appropriate launcher (such as JarLauncher for a jar file) as a Main-Class attribute in the manifest and specify the other properties it needs as manifest entries — principally, by setting a Start-Class property.

The following example shows how to build an executable archive with Ant:

<target name="build" depends="compile">
	<jar destfile="target/${ant.project.name}-${spring-boot.version}.jar" compress="false">
		<mappedresources>
			<fileset dir="target/classes" />
			<globmapper from="*" to="BOOT-INF/classes/*"/>
		</mappedresources>
		<mappedresources>
			<fileset dir="src/main/resources" erroronmissingdir="false"/>
			<globmapper from="*" to="BOOT-INF/classes/*"/>
		</mappedresources>
		<mappedresources>
			<fileset dir="${lib.dir}/runtime" />
			<globmapper from="*" to="BOOT-INF/lib/*"/>
		</mappedresources>
		<zipfileset src="${lib.dir}/loader/spring-boot-loader-jar-${spring-boot.version}.jar" />
		<manifest>
			<attribute name="Main-Class" value="org.springframework.boot.loader.JarLauncher" />
			<attribute name="Start-Class" value="${start-class}" />
		</manifest>
</target>

The Ant Sample has a build.xml file with a manual task that should work if you run it with the following command:

$ ant -lib <folder containing ivy-2.2.jar> clean manual

Then you can run the application with the following command:

$ java -jar target/*.jar

86. Traditional Deployment

Spring Boot supports traditional deployment as well as more modern forms of deployment. This section answers common questions about traditional deployment.

86.1 Create a Deployable War File

The first step in producing a deployable war file is to provide a SpringBootServletInitializer subclass and override its configure method. Doing so makes use of Spring Framework’s Servlet 3.0 support and lets you configure your application when it is launched by the servlet container. Typically, you should update your application’s main class to extend SpringBootServletInitializer , as shown in the following example:

@SpringBootApplication
public class Application extends SpringBootServletInitializer {
	@Override
	protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
		return application.sources(Application.class);
	public static void main(String[] args) throws Exception {
		SpringApplication.run(Application.class, args);
}

The next step is to update your build configuration such that your project produces a war file rather than a jar file. If you use Maven and spring-boot-starter-parent (which configures Maven’s war plugin for you) all you need to do is to modify pom.xml to change the packaging to war, as follows:

<packaging>war</packaging>

If you use Gradle, you need to modify build.gradle to apply the war plugin to the project, as follows:

apply plugin: 'war'

The final step in the process is to ensure that the embedded servlet container does not interfere with the servlet container to which the war file is deployed. To do so, you need to mark the embedded servlet container dependency as being provided.

If you use Maven, the following example marks the servlet container (Tomcat, in this case) as being provided:

<dependencies>
	<!-- … -->
	<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-tomcat</artifactId>
		<scope>provided</scope>
	</dependency>
	<!-- … -->
</dependencies>

If you use Gradle, the following example marks the servlet container (Tomcat, in this case) as being provided:

dependencies {
	providedRuntime 'org.springframework.boot:spring-boot-starter-tomcat'
}

	Note
	`providedRuntime` is preferred to Gradle’s `compileOnly` configuration. Among other limitations, `compileOnly` dependencies are not on the test classpath so any web-based integration tests fail.

If you use the Spring Boot build tools , marking the embedded servlet container dependency as provided produces an executable war file with the provided dependencies packaged in a lib-provided directory. This means that, in addition to being deployable to a servlet container, you can also run your application by using java -jar on the command line.

	Tip
	Take a look at Spring Boot’s sample applications for a Maven-based example of the previously described configuration.

86.2 Create a Deployable War File for Older Servlet Containers

Older Servlet containers do not have support for the ServletContextInitializer bootstrap process used in Servlet 3.0. You can still use Spring and Spring Boot in these containers but you are going to need to add a web.xml to your application and configure it to load an ApplicationContext via a DispatcherServlet .

86.3 Convert an Existing Application to Spring Boot

For a non-web application, it should be easy to convert an existing Spring application to a Spring Boot application. To do so, throw away the code that creates your ApplicationContext and replace it with calls to SpringApplication or SpringApplicationBuilder . Spring MVC web applications are generally amenable to first creating a deployable war application and then migrating it later to an executable war or jar. See the Getting Started Guide on Converting a jar to a war .

To create a deployable war by extending SpringBootServletInitializer (for example, in a class called Application ) and add the Spring Boot @SpringBootApplication annotation, use code similar to that shown in the following example:

@SpringBootApplication
public class Application extends SpringBootServletInitializer {
	@Override
	protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
		// Customize the application or call application.sources(...) to add sources
		// Since our example is itself a @Configuration class (via @SpringBootApplication)
		// we actually don't need to override this method.
		return application;
}

Remember that, whatever you put in the sources is merely a Spring ApplicationContext . Normally, anything that already works should work here. There might be some beans you can remove later and let Spring Boot provide its own defaults for them, but it should be possible to get something working before you need to do that.

Static resources can be moved to /public (or /static or /resources or /META-INF/resources ) in the classpath root. The same applies to messages.properties (which Spring Boot automatically detects in the root of the classpath).

Vanilla usage of Spring DispatcherServlet and Spring Security should require no further changes. If you have other features in your application (for instance, using other servlets or filters), you may need to add some configuration to your Application context, by replacing those elements from the web.xml as follows:

A @Bean of type Servlet or ServletRegistrationBean installs that bean in the container as if it were a <servlet/> and <servlet-mapping/> in web.xml .
A @Bean of type Filter or FilterRegistrationBean behaves similarly (as a <filter/> and <filter-mapping/> ).
An ApplicationContext in an XML file can be added through an @ImportResource in your Application . Alternatively, simple cases where annotation configuration is heavily used already can be recreated in a few lines as @Bean definitions.

Once the war file is working, you can make it executable by adding a main method to your Application , as shown in the following example:

public static void main(String[] args) {
	SpringApplication.run(Application.class, args);
}

Note

If you intend to start your application as a war or as an executable application, you need to share the customizations of the builder in a method that is both available to the SpringBootServletInitializer callback and the main method, in a class similar to the following:

@SpringBootApplication
public class Application extends SpringBootServletInitializer {
	@Override
	protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) {
		return configureApplication(builder);
	public static void main(String[] args) {
		configureApplication(new SpringApplicationBuilder()).run(args);
	private static SpringApplicationBuilder configureApplication(SpringApplicationBuilder builder) {
		return builder.sources(Application.class).bannerMode(Banner.Mode.OFF);
}

Applications can fall into more than one category:

Servlet 3.0+ applications with no web.xml .
Applications with a web.xml .
Applications with a context hierarchy.
Applications without a context hierarchy.

All of these should be amenable to translation, but each might require slightly different techniques.

Servlet 3.0+ applications might translate pretty easily if they already use the Spring Servlet 3.0+ initializer support classes. Normally, all the code from an existing WebApplicationInitializer can be moved into a SpringBootServletInitializer . If your existing application has more than one ApplicationContext (for example, if it uses AbstractDispatcherServletInitializer ) then you might be able to combine all your context sources into a single SpringApplication . The main complication you might encounter is if combining does not work and you need to maintain the context hierarchy. See the entry on building a hierarchy for examples. An existing parent context that contains web-specific features usually needs to be broken up so that all the ServletContextAware components are in the child context.

Applications that are not already Spring applications might be convertible to Spring Boot applications, and the previously mentioned guidance may help. However, you may yet encounter problems. In that case, we suggest asking questions on Stack Overflow with a tag of spring-boot .

86.4 Deploying a WAR to WebLogic

To deploy a Spring Boot application to WebLogic, you must ensure that your servlet initializer directly implements WebApplicationInitializer (even if you extend from a base class that already implements it).

A typical initializer for WebLogic should resemble the following example:

import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.web.SpringBootServletInitializer;
import org.springframework.web.WebApplicationInitializer;
@SpringBootApplication
public class MyApplication extends SpringBootServletInitializer implements WebApplicationInitializer {
}

If you use Logback, you also need to tell WebLogic to prefer the packaged version rather than the version that was pre-installed with the server. You can do so by adding a WEB-INF/weblogic.xml file with the following contents:

<?xml version="1.0" encoding="UTF-8"?>
<wls:weblogic-web-app
	xmlns:wls="http://xmlns.oracle.com/weblogic/weblogic-web-app"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
		http://java.sun.com/xml/ns/javaee/ejb-jar_3_0.xsd
		http://xmlns.oracle.com/weblogic/weblogic-web-app
		http://xmlns.oracle.com/weblogic/weblogic-web-app/1.4/weblogic-web-app.xsd">
	<wls:container-descriptor>
		<wls:prefer-application-packages>
			<wls:package-name>org.slf4j</wls:package-name>
		</wls:prefer-application-packages>
	</wls:container-descriptor>
</wls:weblogic-web-app>

86.5 Deploying a WAR in an Old (Servlet 2.5) Container

Spring Boot uses Servlet 3.0 APIs to initialize the ServletContext (register Servlets and so on), so you cannot use the same application in a Servlet 2.5 container. It is , however, possible to run a Spring Boot application on an older container with some special tools. If you include org.springframework.boot:spring-boot-legacy as a dependency ( maintained separately to the core of Spring Boot and currently available at 1.0.2.RELEASE), all you should need to do is create a web.xml and declare a context listener to create the application context and your filters and servlets. The context listener is a special purpose one for Spring Boot, but the rest of it is normal for a Spring application in Servlet 2.5. The following Maven example shows how to set up a Spring Boot project to run in a Servlet 2.5 container:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
	<context-param>
		<param-name>contextConfigLocation</param-name>
		<param-value>demo.Application</param-value>
	</context-param>
	<listener>
		<listener-class>org.springframework.boot.legacy.context.web.SpringBootContextLoaderListener</listener-class>
	</listener>
	<filter>
		<filter-name>metricsFilter</filter-name>
		<filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
	</filter>
	<filter-mapping>
		<filter-name>metricsFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>
	<servlet>
		<servlet-name>appServlet</servlet-name>
		<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
		<init-param>
			<param-name>contextAttribute</param-name>
			<param-value>org.springframework.web.context.WebApplicationContext.ROOT</param-value>
		</init-param>
		<load-on-startup>1</load-on-startup>
	</servlet>
	<servlet-mapping>
		<servlet-name>appServlet</servlet-name>
		<url-pattern>/</url-pattern>
	</servlet-mapping>
</web-app>

In the preceding example, we use a single application context (the one created by the context listener) and attach it to the DispatcherServlet by using an init parameter. This is normal in a Spring Boot application (you normally only have one application context).

86.6 Use Jedis Instead of Lettuce

By default, the Spring Boot starter ( spring-boot-starter-data-redis ) uses Lettuce . You need to exclude that dependency and include the Jedis one instead. Spring Boot manages these dependencies to help make this process as easy as possible.

The following example shows how to do so in Maven:

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-data-redis</artifactId>
	<exclusions>
		<exclusion>
			<groupId>io.lettuce</groupId>
			<artifactId>lettuce-core</artifactId>
		</exclusion>
	</exclusions>
</dependency>
<dependency>
	<groupId>redis.clients</groupId>
	<artifactId>jedis</artifactId>
</dependency>

The following example shows how to do so in Gradle:

configurations {
	compile.exclude module: "lettuce"
dependencies {
	compile("redis.clients:jedis")
	// ...
}

Part X. Appendices

Appendix A. Common application properties

Various properties can be specified inside your application.properties file, inside your application.yml file, or as command line switches. This appendix provides a list of common Spring Boot properties and references to the underlying classes that consume them.

	Note
	Property contributions can come from additional jar files on your classpath, so you should not consider this an exhaustive list. Also, you can define your own properties.

	Warning
	This sample file is meant as a guide only. Do not copy and paste the entire content into your application. Rather, pick only the properties that you need.

# ===================================================================
# COMMON SPRING BOOT PROPERTIES
# This sample file is provided as a guideline. Do NOT copy it in its
# entirety to your own application.			   ^^^
# ===================================================================
# ----------------------------------------
# CORE PROPERTIES
# ----------------------------------------
# BANNER
banner.charset=UTF-8 # Banner file encoding.
banner.location=classpath:banner.txt # Banner file location.
banner.image.location=classpath:banner.gif # Banner image file location (jpg or png can also be used).
banner.image.width= # Width of the banner image in chars (default 76)
banner.image.height= # Height of the banner image in chars (default based on image height)
banner.image.margin= # Left hand image margin in chars (default 2)
banner.image.invert= # Whether images should be inverted for dark terminal themes (default false)
# LOGGING
logging.config= # Location of the logging configuration file. For instance, `classpath:logback.xml` for Logback
logging.exception-conversion-word=%wEx # Conversion word used when logging exceptions.
logging.file= # Log file name. For instance, `myapp.log`
logging.file.max-history= # Maximum of archive log files to keep. Only supported with the default logback setup.
logging.file.max-size= # Maximum log file size. Only supported with the default logback setup.
logging.level.*= # Log levels severity mapping. For instance, `logging.level.org.springframework=DEBUG`
logging.path= # Location of the log file. For instance, `/var/log`
logging.pattern.console= # Appender pattern for output to the console. Supported only with the default Logback setup.
logging.pattern.file= # Appender pattern for output to a file. Supported only with the default Logback setup.
logging.pattern.level= # Appender pattern for log level (default: %5p). Supported only with the default Logback setup.
logging.pattern.dateformat= # Appender pattern for log dateformat (default yyyy-MM-dd HH:mm:ss.SSS). Only supported with the default logback setup.
logging.register-shutdown-hook=false # Register a shutdown hook for the logging system when it is initialized.
# AOP
spring.aop.auto=true # Add @EnableAspectJAutoProxy.
spring.aop.proxy-target-class=true # Whether subclass-based (CGLIB) proxies are to be created (true), as opposed to standard Java interface-based proxies (false).
# IDENTITY (ContextIdApplicationContextInitializer)
spring.application.index= # Application index.
spring.application.name= # Application name.
# ADMIN (SpringApplicationAdminJmxAutoConfiguration)
spring.application.admin.enabled=false # Whether to enable admin features for the application.
spring.application.admin.jmx-name=org.springframework.boot:type=Admin,name=SpringApplication # JMX name of the application admin MBean.
# AUTO-CONFIGURATION
spring.autoconfigure.exclude= # Auto-configuration classes to exclude.
# SPRING CORE
spring.beaninfo.ignore=true # Whether to skip search of BeanInfo classes.
# SPRING CACHE (CacheProperties)
spring.cache.cache-names= # Comma-separated list of cache names to create if supported by the underlying cache manager.
spring.cache.caffeine.spec= # The spec to use to create caches. See CaffeineSpec for more details on the spec format.
spring.cache.couchbase.expiration=0ms # Entry expiration in milliseconds. By default, the entries never expire.
spring.cache.ehcache.config= # The location of the configuration file to use to initialize EhCache.
spring.cache.infinispan.config= # The location of the configuration file to use to initialize Infinispan.
spring.cache.jcache.config= # The location of the configuration file to use to initialize the cache manager.
spring.cache.jcache.provider= # Fully qualified name of the CachingProvider implementation to use to retrieve the JSR-107 compliant cache manager. Needed only if more than one JSR-107 implementation is available on the classpath.
spring.cache.redis.cache-null-values=true # Allow caching null values.
spring.cache.redis.key-prefix= # Key prefix.
spring.cache.redis.time-to-live=0ms # Entry expiration. By default the entries never expire.
spring.cache.redis.use-key-prefix=true # Whether to use the key prefix when writing to Redis.
spring.cache.type= # Cache type. By default, auto-detected according to the environment.
# SPRING CONFIG - using environment property only (ConfigFileApplicationListener)
spring.config.additional-location= # Config file locations used in addition to the defaults.
spring.config.location= # Config file locations.
spring.config.name=application # Config file name.
# HAZELCAST (HazelcastProperties)
spring.hazelcast.config= # The location of the configuration file to use to initialize Hazelcast.
# PROJECT INFORMATION (ProjectInfoProperties)
spring.info.build.location=classpath:META-INF/build-info.properties # Location of the generated build-info.properties file.
spring.info.git.location=classpath:git.properties # Location of the generated git.properties file.
# JMX
spring.jmx.default-domain= # JMX domain name.
spring.jmx.enabled=true # Expose management beans to the JMX domain.
spring.jmx.server=mbeanServer # MBeanServer bean name.
# Email (MailProperties)
spring.mail.default-encoding=UTF-8 # Default MimeMessage encoding.
spring.mail.host= # SMTP server host. For instance, `smtp.example.com`
spring.mail.jndi-name= # Session JNDI name. When set, takes precedence over other mail settings.
spring.mail.password= # Login password of the SMTP server.
spring.mail.port= # SMTP server port.
spring.mail.properties.*= # Additional JavaMail session properties.
spring.mail.protocol=smtp # Protocol used by the SMTP server.
spring.mail.test-connection=false # Whether to test that the mail server is available on startup.
spring.mail.username= # Login user of the SMTP server.
# APPLICATION SETTINGS (SpringApplication)
spring.main.banner-mode=console # Mode used to display the banner when the application runs.
spring.main.sources= # Sources (class names, package names, or XML resource locations) to include in the ApplicationContext.
spring.main.web-application-type= # Flag to explicitly request a specific type of web application. If not set, auto-detected based on the classpath.
# FILE ENCODING (FileEncodingApplicationListener)
spring.mandatory-file-encoding= # Expected character encoding the application must use.
# INTERNATIONALIZATION (MessageSourceProperties)
spring.messages.always-use-message-format=false # Whether to always apply the MessageFormat rules, parsing even messages without arguments.
spring.messages.basename=messages # Comma-separated list of basenames, each following the ResourceBundle convention.
spring.messages.cache-duration=-1 # Loaded resource bundle files cache duration. When not set, bundles are cached forever.
spring.messages.encoding=UTF-8 # Message bundles encoding.
spring.messages.fallback-to-system-locale=true # Whether to fall back to the system Locale if no files for a specific Locale have been found.
spring.messages.use-code-as-default-message=false # Whether to use the message code as the default message instead of throwing a "NoSuchMessageException". Recommended during development only.
# OUTPUT
spring.output.ansi.enabled=detect # Configures the ANSI output.
# PID FILE (ApplicationPidFileWriter)
spring.pid.fail-on-write-error= # Fails if ApplicationPidFileWriter is used but it cannot write the PID file.
spring.pid.file= # Location of the PID file to write (if ApplicationPidFileWriter is used).
# PROFILES
spring.profiles.active= # Comma-separated list (or list if using YAML) of active profiles.
spring.profiles.include= # Unconditionally activate the specified comma-separated list of profiles (or list of profiles if using YAML).
# QUARTZ SCHEDULER (QuartzProperties)
spring.quartz.job-store-type=memory # Quartz job store type.
spring.quartz.properties.*= # Additional Quartz Scheduler properties.
spring.quartz.jdbc.initialize-schema=embedded # Database schema initialization mode.
spring.quartz.jdbc.schema=classpath:org/quartz/impl/jdbcjobstore/tables_@@platform@@.sql # Path to the SQL file to use to initialize the database schema.
# REACTOR (ReactorCoreProperties)
spring.reactor.stacktrace-mode.enabled=false # Whether Reactor should collect stacktrace information at runtime.
# SENDGRID (SendGridAutoConfiguration)
spring.sendgrid.api-key= # SendGrid API key.
spring.sendgrid.proxy.host= # SendGrid proxy host.
spring.sendgrid.proxy.port= # SendGrid proxy port.
# ----------------------------------------
# WEB PROPERTIES
# ----------------------------------------
# EMBEDDED SERVER CONFIGURATION (ServerProperties)
server.address= # Network address to which the server should bind.
server.compression.enabled=false # Whether response compression is enabled.
server.compression.excluded-user-agents= # List of user-agents to exclude from compression.
server.compression.mime-types=text/html,text/xml,text/plain,text/css,text/javascript,application/javascript # Comma-separated list of MIME types that should be compressed.
server.compression.min-response-size=2048 # Minimum response size that is required for compression to be performed.
server.connection-timeout= # Time that connectors wait for another HTTP request before closing the connection. When not set, the connector's container-specific default is used. Use a value of -1 to indicate no (that is, an infinite) timeout.
server.display-name=application # Display name of the application.
server.max-http-header-size=0 # Maximum size, in bytes, of the HTTP message header.
server.error.include-exception=false # Include the "exception" attribute.
server.error.include-stacktrace=never # When to include a "stacktrace" attribute.
server.error.path=/error # Path of the error controller.
server.error.whitelabel.enabled=true # Enable the default error page displayed in browsers in case of a server error.
server.http2.enabled=true # Whether to enable HTTP/2 support, if the current environment supports it.
server.jetty.acceptors= # Number of acceptor threads to use.
server.jetty.accesslog.append=false # Append to log.
server.jetty.accesslog.date-format=dd/MMM/yyyy:HH:mm:ss Z # Timestamp format of the request log.
server.jetty.accesslog.enabled=false # Enable access log.
server.jetty.accesslog.extended-format=false # Enable extended NCSA format.
server.jetty.accesslog.file-date-format= # Date format to place in log file name.
server.jetty.accesslog.filename= # Log filename. If not specified, logs redirect to "System.err".
server.jetty.accesslog.locale= # Locale of the request log.
server.jetty.accesslog.log-cookies=false # Enable logging of the request cookies.
server.jetty.accesslog.log-latency=false # Enable logging of request processing time.
server.jetty.accesslog.log-server=false # Enable logging of the request hostname.
server.jetty.accesslog.retention-period=31 # Number of days before rotated log files are deleted.
server.jetty.accesslog.time-zone=GMT # Timezone of the request log.
server.jetty.max-http-post-size=0 # Maximum size, in bytes, of the HTTP post or put content.
server.jetty.selectors= # Number of selector threads to use.
server.port=8080 # Server HTTP port.
server.server-header= # Value to use for the Server response header (if empty, no header is sent)
server.use-forward-headers= # Whether X-Forwarded-* headers should be applied to the HttpRequest.
server.servlet.context-parameters.*= # Servlet context init parameters
server.servlet.context-path= # Context path of the application.
server.servlet.jsp.class-name=org.apache.jasper.servlet.JspServlet # The class name of the JSP servlet.
server.servlet.jsp.init-parameters.*= # Init parameters used to configure the JSP servlet.
server.servlet.jsp.registered=true # Whether the JSP servlet is registered.
server.servlet.path=/ # Path of the main dispatcher servlet.
server.session.cookie.comment= # Comment for the session cookie.
server.session.cookie.domain= # Domain for the session cookie.
server.session.cookie.http-only= # "HttpOnly" flag for the session cookie.
server.session.cookie.max-age= # Maximum age of the session cookie. If a duration suffix is not specified, seconds will be used.
server.session.cookie.name= # Session cookie name.
server.session.cookie.path= # Path of the session cookie.
server.session.cookie.secure= # "Secure" flag for the session cookie.
server.session.persistent=false # Whether to persist session data between restarts.
server.session.store-dir= # Directory used to store session data.
server.session.timeout= # Session timeout. If a duration suffix is not specified, seconds will be used.
server.session.tracking-modes= # Session tracking modes (one or more of the following: "cookie", "url", "ssl").
server.ssl.ciphers= # Supported SSL ciphers.
server.ssl.client-auth= # Whether client authentication is wanted ("want") or needed ("need"). Requires a trust store.
server.ssl.enabled= # Enable SSL support.
server.ssl.enabled-protocols= # Enabled SSL protocols.
server.ssl.key-alias= # Alias that identifies the key in the key store.
server.ssl.key-password= # Password used to access the key in the key store.
server.ssl.key-store= # Path to the key store that holds the SSL certificate (typically a jks file).
server.ssl.key-store-password= # Password used to access the key store.
server.ssl.key-store-provider= # Provider for the key store.
server.ssl.key-store-type= # Type of the key store.
server.ssl.protocol=TLS # SSL protocol to use.
server.ssl.trust-store= # Trust store that holds SSL certificates.
server.ssl.trust-store-password= # Password used to access the trust store.
server.ssl.trust-store-provider= # Provider for the trust store.
server.ssl.trust-store-type= # Type of the trust store.
server.tomcat.accept-count= # Maximum queue length for incoming connection requests when all possible request processing threads are in use.
server.tomcat.accesslog.buffered=true # Whether to buffer output such that it is flushed only periodically.
server.tomcat.accesslog.directory=logs # Directory in which log files are created. Can be absolute or relative to the Tomcat base dir.
server.tomcat.accesslog.enabled=false # Enable access log.
server.tomcat.accesslog.file-date-format=.yyyy-MM-dd # Date format to place in the log file name.
server.tomcat.accesslog.pattern=common # Format pattern for access logs.
server.tomcat.accesslog.prefix=access_log # Log file name prefix.
server.tomcat.accesslog.rename-on-rotate=false # Whether to defer inclusion of the date stamp in the file name until rotate time.
server.tomcat.accesslog.request-attributes-enabled=false # Set request attributes for the IP address, Hostname, protocol, and port used for the request.
server.tomcat.accesslog.rotate=true # Whether to enable access log rotation.
server.tomcat.accesslog.suffix=.log # Log file name suffix.
server.tomcat.additional-tld-skip-patterns= # Comma-separated list of additional patterns that match jars to ignore for TLD scanning.
server.tomcat.background-processor-delay=30s # Delay between the invocation of backgroundProcess methods. If a duration suffix is not specified, seconds will be used.
server.tomcat.basedir= # Tomcat base directory. If not specified, a temporary directory is used.
server.tomcat.internal-proxies=10\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}|\\
		192\\.168\\.\\d{1,3}\\.\\d{1,3}|\\
		169\\.254\\.\\d{1,3}\\.\\d{1,3}|\\
		127\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}|\\
		172\\.1[6-9]{1}\\.\\d{1,3}\\.\\d{1,3}|\\
		172\\.2[0-9]{1}\\.\\d{1,3}\\.\\d{1,3}|\\
		172\\.3[0-1]{1}\\.\\d{1,3}\\.\\d{1,3} # regular expression matching trusted IP addresses.
server.tomcat.max-connections= # Maximum number of connections that the server accepts and processes at any given time.
server.tomcat.max-http-header-size=0 # Maximum size, in bytes, of the HTTP message header.
server.tomcat.max-http-post-size=0 # Maximum size, in bytes, of the HTTP post content.
server.tomcat.max-threads=0 # Maximum number of worker threads.
server.tomcat.min-spare-threads=0 # Minimum number of worker threads.
server.tomcat.port-header=X-Forwarded-Port # Name of the HTTP header used to override the original port value.
server.tomcat.protocol-header= # Header that holds the incoming protocol, usually named "X-Forwarded-Proto".
server.tomcat.protocol-header-https-value=https # Value of the protocol header indicating whether the incoming request uses SSL.
server.tomcat.redirect-context-root= # Whether requests to the context root should be redirected by appending a / to the path.
server.tomcat.remote-ip-header= # Name of the HTTP header from which the remote IP is extracted. For instance, `X-FORWARDED-FOR`.
server.tomcat.resource.cache-ttl= # Time-to-live of the static resource cache.
server.tomcat.uri-encoding=UTF-8 # Character encoding to use to decode the URI.
server.undertow.accesslog.dir= # Undertow access log directory.
server.undertow.accesslog.enabled=false # Whether to enable the access log.
server.undertow.accesslog.pattern=common # Format pattern for access logs.
server.undertow.accesslog.prefix=access_log. # Log file name prefix.
server.undertow.accesslog.rotate=true # Whether to enable access log rotation.
server.undertow.accesslog.suffix=log # Log file name suffix.
server.undertow.buffer-size= # Size of each buffer, in bytes.
server.undertow.direct-buffers= # Whether to allocate buffers outside the Java heap.
server.undertow.io-threads= # Number of I/O threads to create for the worker.
server.undertow.eager-filter-init=true # Whether servlet filters should be initialized on startup.
server.undertow.max-http-post-size=0 # Maximum size, in bytes, of the HTTP post content.
server.undertow.worker-threads= # Number of worker threads.
# FREEMARKER (FreeMarkerProperties)
spring.freemarker.allow-request-override=false # Whether HttpServletRequest attributes are allowed to override (hide) controller generated model attributes of the same name.
spring.freemarker.allow-session-override=false # Whether HttpSession attributes are allowed to override (hide) controller generated model attributes of the same name.
spring.freemarker.cache=false # Whether to enable template caching.
spring.freemarker.charset=UTF-8 # Template encoding.
spring.freemarker.check-template-location=true # Whether to check that the templates location exists.
spring.freemarker.content-type=text/html # Content-Type value.
spring.freemarker.enabled=true # Whether to enable MVC view resolution for this technology.
spring.freemarker.expose-request-attributes=false # Whether all request attributes should be added to the model prior to merging with the template.
spring.freemarker.expose-session-attributes=false # Whether all HttpSession attributes should be added to the model prior to merging with the template.
spring.freemarker.expose-spring-macro-helpers=true # Whether to expose a RequestContext for use by Spring's macro library, under the name "springMacroRequestContext".
spring.freemarker.prefer-file-system-access=true # Whether to prefer file system access for template loading. File system access enables hot detection of template changes.
spring.freemarker.prefix= # Prefix that gets prepended to view names when building a URL.
spring.freemarker.request-context-attribute= # Name of the RequestContext attribute for all views.
spring.freemarker.settings.*= # Well-known FreeMarker keys which are passed to FreeMarker's Configuration.
spring.freemarker.suffix=.ftl # Suffix that gets appended to view names when building a URL.
spring.freemarker.template-loader-path=classpath:/templates/ # Comma-separated list of template paths.
spring.freemarker.view-names= # White list of view names that can be resolved.
# GROOVY TEMPLATES (GroovyTemplateProperties)
spring.groovy.template.allow-request-override=false # Whether HttpServletRequest attributes are allowed to override (hide) controller generated model attributes of the same name.
spring.groovy.template.allow-session-override=false # Whether HttpSession attributes are allowed to override (hide) controller generated model attributes of the same name.
spring.groovy.template.cache= # Whether to enable template caching.
spring.groovy.template.charset=UTF-8 # Template encoding.
spring.groovy.template.check-template-location=true # Check that the templates location exists.
spring.groovy.template.configuration.*= # See GroovyMarkupConfigurer
spring.groovy.template.content-type=test/html # Content-Type value.
spring.groovy.template.enabled=true # Whether to enable MVC view resolution for this technology.
spring.groovy.template.expose-request-attributes=false # Whether all request attributes should be added to the model prior to merging with the template.
spring.groovy.template.expose-session-attributes=false # Whether all HttpSession attributes should be added to the model prior to merging with the template.
spring.groovy.template.expose-spring-macro-helpers=true # Whether to expose a RequestContext for use by Spring's macro library, under the name "springMacroRequestContext".
spring.groovy.template.prefix= # Prefix that gets prepended to view names when building a URL.
spring.groovy.template.request-context-attribute= # Name of the RequestContext attribute for all views.
spring.groovy.template.resource-loader-path=classpath:/templates/ # Template path.
spring.groovy.template.suffix=.tpl # Suffix that gets appended to view names when building a URL.
spring.groovy.template.view-names= # White list of view names that can be resolved.
# SPRING HATEOAS (HateoasProperties)
spring.hateoas.use-hal-as-default-json-media-type=true # Whether application/hal+json responses should be sent to requests that accept application/json.
# HTTP message conversion
spring.http.converters.preferred-json-mapper= # Preferred JSON mapper to use for HTTP message conversion. By default, auto-detected according to the environment.
# HTTP encoding (HttpEncodingProperties)
spring.http.encoding.charset=UTF-8 # Charset of HTTP requests and responses. Added to the "Content-Type" header if not set explicitly.
spring.http.encoding.enabled=true # Whether to enable http encoding support.
spring.http.encoding.force= # Whether to force the encoding to the configured charset on HTTP requests and responses.
spring.http.encoding.force-request= # Whether to force the encoding to the configured charset on HTTP requests. Defaults to true when "force" has not been specified.
spring.http.encoding.force-response= # Whether to force the encoding to the configured charset on HTTP responses.
spring.http.encoding.mapping= # Locale in which to encode mapping.
# MULTIPART (MultipartProperties)
spring.servlet.multipart.enabled=true # Whether to enable support of multipart uploads.
spring.servlet.multipart.file-size-threshold=0 # Threshold after which files are written to disk. Values can use the suffixes "MB" or "KB" to indicate megabytes or kilobytes, respectively.
spring.servlet.multipart.location= # Intermediate location of uploaded files.
spring.servlet.multipart.max-file-size=1MB # Max file size. Values can use the suffixes "MB" or "KB" to indicate megabytes or kilobytes, respectively.
spring.servlet.multipart.max-request-size=10MB # Max request size. Values can use the suffixes "MB" or "KB" to indicate megabytes or kilobytes, respectively.
spring.servlet.multipart.resolve-lazily=false # Whether to resolve the multipart request lazily at the time of file or parameter access.
# JACKSON (JacksonProperties)
spring.jackson.date-format= # Date format string or a fully-qualified date format class name. For instance, `yyyy-MM-dd HH:mm:ss`.
spring.jackson.default-property-inclusion= # Controls the inclusion of properties during serialization. Configured with one of the values in Jackson's JsonInclude.Include enumeration.
spring.jackson.deserialization.*= # Jackson on/off features that affect the way Java objects are deserialized.
spring.jackson.generator.*= # Jackson on/off features for generators.
spring.jackson.joda-date-time-format= # Joda date time format string. If not configured, "date-format" is used as a fallback if it is configured with a format string.
spring.jackson.locale= # Locale used for formatting.
spring.jackson.mapper.*= # Jackson general purpose on/off features.
spring.jackson.parser.*= # Jackson on/off features for parsers.
spring.jackson.property-naming-strategy= # One of the constants on Jackson's PropertyNamingStrategy. Can also be a fully-qualified class name of a PropertyNamingStrategy subclass.
spring.jackson.serialization.*= # Jackson on/off features that affect the way Java objects are serialized.
spring.jackson.time-zone= #  Time zone used when formatting dates. For instance, "America/Los_Angeles" or "GMT+10".
# JERSEY (JerseyProperties)
spring.jersey.application-path= # Path that serves as the base URI for the application. If specified, overrides the value of "@ApplicationPath".
spring.jersey.filter.order=0 # Jersey filter chain order.
spring.jersey.init.*= # Init parameters to pass to Jersey through the servlet or filter.
spring.jersey.servlet.load-on-startup=-1 # Load on startup priority of the Jersey servlet.
spring.jersey.type=servlet # Jersey integration type.
# SPRING LDAP (LdapProperties)
spring.ldap.urls= # LDAP URLs of the server.
spring.ldap.base= # Base suffix from which all operations should originate.
spring.ldap.username= # Login username of the server.
spring.ldap.password= # Login password of the server.
spring.ldap.base-environment.*= # LDAP specification settings.
# EMBEDDED LDAP (EmbeddedLdapProperties)
spring.ldap.embedded.base-dn= # The base DN
spring.ldap.embedded.credential.username= # Embedded LDAP username.
spring.ldap.embedded.credential.password= # Embedded LDAP password.
spring.ldap.embedded.ldif=classpath:schema.ldif # Schema (LDIF) script resource reference.
spring.ldap.embedded.port= # Embedded LDAP port.
spring.ldap.embedded.validation.enabled=true # Whether to enable LDAP schema validation.
spring.ldap.embedded.validation.schema= # Path to the custom schema.
# MUSTACHE TEMPLATES (MustacheAutoConfiguration)
spring.mustache.allow-request-override= # Whether HttpServletRequest attributes are allowed to override (hide) controller generated model attributes of the same name.
spring.mustache.allow-session-override= # Whether HttpSession attributes are allowed to override (hide) controller generated model attributes of the same name.
spring.mustache.cache= # Whether to enable template caching.
spring.mustache.charset= # Template encoding.
spring.mustache.check-template-location= # Whether to check that the templates location exists.
spring.mustache.content-type= # Content-Type value.
spring.mustache.enabled= # Whether to enable MVC view resolution for this technology.
spring.mustache.expose-request-attributes= # Whether all request attributes should be added to the model prior to merging with the template.
spring.mustache.expose-session-attributes= # Whether all HttpSession attributes should be added to the model prior to merging with the template.
spring.mustache.expose-spring-macro-helpers= # Whether to expose a RequestContext for use by Spring's macro library under the name "springMacroRequestContext".
spring.mustache.prefix=classpath:/templates/ # Prefix to apply to template names.
spring.mustache.request-context-attribute= # Name of the RequestContext attribute for all views.
spring.mustache.suffix=.mustache # Suffix to apply to template names.
spring.mustache.view-names= # White list of view names that can be resolved.
# SPRING MVC (WebMvcProperties)
spring.mvc.async.request-timeout= # Amount of time before asynchronous request handling times out.
spring.mvc.date-format= # Date format to use. For instance, `dd/MM/yyyy`.
spring.mvc.dispatch-trace-request=false # Whether to dispatch TRACE requests to the FrameworkServlet doService method.
spring.mvc.dispatch-options-request=true # Whether to dispatch OPTIONS requests to the FrameworkServlet doService method.
spring.mvc.favicon.enabled=true # Whether to enable resolution of favicon.ico.
spring.mvc.formcontent.putfilter.enabled=true # Whether to enable Spring's HttpPutFormContentFilter.
spring.mvc.ignore-default-model-on-redirect=true # Whether the content of the "default" model should be ignored during redirect scenarios.
spring.mvc.locale= # Locale to use. By default, this locale is overridden by the "Accept-Language" header.
spring.mvc.locale-resolver=accept-header # Define how the locale should be resolved.
spring.mvc.log-resolved-exception=false # Whether to enable warn logging of exceptions resolved by a "HandlerExceptionResolver".
spring.mvc.media-types.*= # Maps file extensions to media types for content negotiation.
spring.mvc.message-codes-resolver-format= # Formatting strategy for message codes. For instance, `PREFIX_ERROR_CODE`.
spring.mvc.servlet.load-on-startup=-1 # Load on startup priority of the Spring Web Services servlet.
spring.mvc.static-path-pattern=/** # Path pattern used for static resources.
spring.mvc.throw-exception-if-no-handler-found=false # Whether a "NoHandlerFoundException" should be thrown if no Handler was found to process a request.
spring.mvc.view.prefix= # Spring MVC view prefix.
spring.mvc.view.suffix= # Spring MVC view suffix.
# SPRING RESOURCES HANDLING (ResourceProperties)
spring.resources.add-mappings=true # Whether to enable default resource handling.
spring.resources.cache.cachecontrol.max-age= # Maximum time the response should be cached, in seconds if no duration suffix is not specified.
spring.resources.cache.cachecontrol.no-cache= # Indicate that the cached response can be reused only if re-validated with the server.
spring.resources.cache.cachecontrol.no-store= # Indicate to not cache the response in any case.
spring.resources.cache.cachecontrol.must-revalidate= # Indicate that once it has become stale, a cache must not use the response without re-validating it with the server.
spring.resources.cache.cachecontrol.no-transform= # Indicate intermediaries (caches and others) that they should not transform the response content.
spring.resources.cache.cachecontrol.cache-public= # Indicate that any cache may store the response.
spring.resources.cache.cachecontrol.cache-private= # Indicate that the response message is intended for a single user and must not be stored by a shared cache.
spring.resources.cache.cachecontrol.proxy-revalidate= # Same meaning as the "must-revalidate" directive, except that it does not apply to private caches.
spring.resources.cache.cachecontrol.stale-while-revalidate= # Maximum time the response can be served after it becomes stale, in seconds if no duration suffix is not specified.
spring.resources.cache.cachecontrol.stale-if-error= # Maximum time the response may be used when errors are encountered, in seconds if no duration suffix is not specified.
spring.resources.cache.cachecontrol.s-max-age= # Maximum time the response should be cached by shared caches, in seconds if no duration suffix is not specified.
spring.resources.cache.period= # Cache period for the resources served by the resource handler. If a duration suffix is not specified, seconds will be used.
spring.resources.chain.cache=true # Whether to enable caching in the Resource chain.
spring.resources.chain.enabled= # Whether to enable the Spring Resource Handling chain. By default, disabled unless at least one strategy has been enabled.
spring.resources.chain.gzipped=false # Whether to enable resolution of already gzipped resources.
spring.resources.chain.html-application-cache=false # Whether to enable HTML5 application cache manifest rewriting.
spring.resources.chain.strategy.content.enabled=false # Enable the content Version Strategy.
spring.resources.chain.strategy.content.paths=/** # Comma-separated list of patterns to apply to the content Version Strategy.
spring.resources.chain.strategy.content.enabled=false # Whether to enable the content Version Strategy.
spring.resources.chain.strategy.fixed.enabled=false # Whether to enable the fixed Version Strategy.
spring.resources.chain.strategy.fixed.paths=/** # Comma-separated list of patterns to apply to the fixed Version Strategy.
spring.resources.chain.strategy.fixed.version= # Version string to use for the fixed Version Strategy.
spring.resources.static-locations=classpath:/META-INF/resources/,classpath:/resources/,classpath:/static/,classpath:/public/ # Locations of static resources.
# SPRING SESSION (SessionProperties)
spring.session.store-type= # Session store type.
spring.session.servlet.filter-order=-2147483598 # Session repository filter order.
spring.session.servlet.filter-dispatcher-types=ASYNC,ERROR,REQUEST # Session repository filter dispatcher types.
# SPRING SESSION HAZELCAST (HazelcastSessionProperties)
spring.session.hazelcast.flush-mode=on-save # Sessions flush mode.
spring.session.hazelcast.map-name=spring:session:sessions # Name of the map used to store sessions.
# SPRING SESSION JDBC (JdbcSessionProperties)
spring.session.jdbc.cleanup-cron=0 * * * * * # Cron expression for expired session cleanup job.
spring.session.jdbc.initialize-schema=embedded # Database schema initialization mode.
spring.session.jdbc.schema=classpath:org/springframework/session/jdbc/schema-@@platform@@.sql # Path to the SQL file to use to initialize the database schema.
spring.session.jdbc.table-name=SPRING_SESSION # Name of the database table used to store sessions.
# SPRING SESSION MONGODB (MongoSessionProperties)
spring.session.mongodb.collection-name=sessions # Collection name used to store sessions.
# SPRING SESSION REDIS (RedisSessionProperties)
spring.session.redis.cleanup-cron=0 * * * * * # Cron expression for expired session cleanup job.
spring.session.redis.flush-mode=on-save # Sessions flush mode.
spring.session.redis.namespace=spring:session # Namespace for keys used to store sessions.
# THYMELEAF (ThymeleafAutoConfiguration)
spring.thymeleaf.cache=true # Whether to enable template caching.
spring.thymeleaf.check-template=true # Whether to check that the template exists before rendering it.
spring.thymeleaf.check-template-location=true # Whether to check that the templates location exists.
spring.thymeleaf.enabled=true # Whether to enable Thymeleaf view resolution for Web frameworks.
spring.thymeleaf.enable-spring-el-compiler=false # Enable the SpringEL compiler in SpringEL expressions.
spring.thymeleaf.encoding=UTF-8 # Template files encoding.
spring.thymeleaf.excluded-view-names= # Comma-separated list of view names that should be excluded from resolution.
spring.thymeleaf.mode=HTML5 # Template mode to be applied to templates. See also Thymeleaf's TemplateMode enum.
spring.thymeleaf.prefix=classpath:/templates/ # Prefix that gets prepended to view names when building a URL.
spring.thymeleaf.reactive.chunked-mode-view-names= # Comma-separated list of view names (patterns allowed) that should be the only ones executed in CHUNKED mode when a max chunk size is set.
spring.thymeleaf.reactive.full-mode-view-names= # Comma-separated list of view names (patterns allowed) that should be executed in FULL mode even if a max chunk size is set.
spring.thymeleaf.reactive.max-chunk-size= # Maximum size of data buffers used for writing to the response, in bytes.
spring.thymeleaf.reactive.media-types= # Media types supported by the view technology.
spring.thymeleaf.servlet.content-type=text/html # Content-Type value written to HTTP responses.
spring.thymeleaf.suffix=.html # Suffix that gets appended to view names when building a URL.
spring.thymeleaf.template-resolver-order= # Order of the template resolver in the chain.
spring.thymeleaf.view-names= # Comma-separated list of view names that can be resolved.
# SPRING WEB FLUX (WebFluxProperties)
spring.webflux.static-path-pattern=/** # Path pattern used for static resources.
# SPRING WEB SERVICES (WebServicesProperties)
spring.webservices.path=/services # Path that serves as the base URI for the services.
spring.webservices.servlet.init= # Servlet init parameters to pass to Spring Web Services.
spring.webservices.servlet.load-on-startup=-1 # Load on startup priority of the Spring Web Services servlet.
spring.webservices.wsdl-locations= # Comma-separated list of locations of WSDLs and accompanying XSDs to be exposed as beans.
# ----------------------------------------
# SECURITY PROPERTIES
# ----------------------------------------
# SECURITY (SecurityProperties)
spring.security.filter.order=0 # Security filter chain order.
spring.security.filter.dispatcher-types=ASYNC,ERROR,REQUEST # Security filter chain dispatcher types.
# SECURITY OAUTH2 CLIENT (OAuth2ClientProperties)
spring.security.oauth2.client.provider.*= # OAuth provider details.
spring.security.oauth2.client.registration.*= # OAuth client registrations.
# ----------------------------------------
# DATA PROPERTIES
# ----------------------------------------
# FLYWAY (FlywayProperties)
spring.flyway.allow-mixed-migrations= #
spring.flyway.baseline-description= #
spring.flyway.baseline-on-migrate= #
spring.flyway.baseline-version=1 # Version to start migration
spring.flyway.check-location=true # Whether to check that migration scripts location exists.
spring.flyway.clean-disabled= #
spring.flyway.clean-on-validation-error= #
spring.flyway.enabled=true # Whether to enable flyway.
spring.flyway.encoding= #
spring.flyway.group= #
spring.flyway.ignore-failed-future-migration= #
spring.flyway.ignore-future-migrations= #
spring.flyway.ignore-missing-migrations= #
spring.flyway.init-sqls= # SQL statements to execute to initialize a connection immediately after obtaining it.
spring.flyway.installed-by= #
spring.flyway.locations=classpath:db/migration # The locations of migrations scripts.
spring.flyway.mixed= #
spring.flyway.out-of-order= #
spring.flyway.password= # JDBC password to use if you want Flyway to create its own DataSource.
spring.flyway.placeholder-prefix= #
spring.flyway.placeholder-replacement= #
spring.flyway.placeholder-suffix= #
spring.flyway.placeholders.*= #
spring.flyway.repeatable-sql-migration-prefix= #
spring.flyway.schemas= # schemas to update
spring.flyway.skip-default-callbacks= #
spring.flyway.skip-default-resolvers= #
spring.flyway.sql-migration-prefix=V #
spring.flyway.sql-migration-separator= #
spring.flyway.sql-migration-suffix=.sql #
spring.flyway.table= #
spring.flyway.target= #
spring.flyway.url= # JDBC url of the database to migrate. If not set, the primary configured data source is used.
spring.flyway.user= # Login user of the database to migrate.
spring.flyway.validate-on-migrate= #
# LIQUIBASE (LiquibaseProperties)
spring.liquibase.change-log=classpath:/db/changelog/db.changelog-master.yaml # Change log configuration path.
spring.liquibase.check-change-log-location=true # Whether to check that the change log location exists.
spring.liquibase.contexts= # Comma-separated list of runtime contexts to use.
spring.liquibase.default-schema= # Default database schema.
spring.liquibase.drop-first=false # Whether to first drop the database schema.
spring.liquibase.enabled=true # Whether to enable Liquibase support.
spring.liquibase.labels= # Comma-separated list of runtime labels to use.
spring.liquibase.parameters.*= # Change log parameters.
spring.liquibase.password= # Login password of the database to migrate.
spring.liquibase.rollback-file= # File to which rollback SQL is written when an update is performed.
spring.liquibase.url= # JDBC URL of the database to migrate. If not set, the primary configured data source is used.
spring.liquibase.user= # Login user of the database to migrate.
# COUCHBASE (CouchbaseProperties)
spring.couchbase.bootstrap-hosts= # Couchbase nodes (host or IP address) to bootstrap from.
spring.couchbase.bucket.name=default # Name of the bucket to connect to.
spring.couchbase.bucket.password=  # Password of the bucket.
spring.couchbase.env.endpoints.key-value=1 # Number of sockets per node against the Key/value service.
spring.couchbase.env.endpoints.query=1 # Number of sockets per node against the Query (N1QL) service.
spring.couchbase.env.endpoints.view=1 # Number of sockets per node against the view service.
spring.couchbase.env.ssl.enabled= # Whether to enable SSL support. Enabled automatically if a "keyStore" is provided, unless specified otherwise.
spring.couchbase.env.ssl.key-store= # Path to the JVM key store that holds the certificates.
spring.couchbase.env.ssl.key-store-password= # Password used to access the key store.
spring.couchbase.env.timeouts.connect=5000ms # Bucket connections timeouts.
spring.couchbase.env.timeouts.key-value=2500ms # Blocking operations performed on a specific key timeout.
spring.couchbase.env.timeouts.query=7500ms # N1QL query operations timeout.
spring.couchbase.env.timeouts.socket-connect=1000ms # Socket connect connections timeout.
spring.couchbase.env.timeouts.view=7500ms # Regular and geospatial view operations timeout.
# DAO (PersistenceExceptionTranslationAutoConfiguration)
spring.dao.exceptiontranslation.enabled=true # Whether to enable the PersistenceExceptionTranslationPostProcessor.
# CASSANDRA (CassandraProperties)
spring.data.cassandra.cluster-name= # Name of the Cassandra cluster.
spring.data.cassandra.compression=none # Compression supported by the Cassandra binary protocol.
spring.data.cassandra.connect-timeout= # Socket option: connection time out.
spring.data.cassandra.consistency-level= # Queries consistency level.
spring.data.cassandra.contact-points=localhost # Comma-separated list of cluster node addresses.
spring.data.cassandra.fetch-size= # Queries default fetch size.
spring.data.cassandra.keyspace-name= # Keyspace name to use.
spring.data.cassandra.load-balancing-policy= # Class name of the load balancing policy.
spring.data.cassandra.port= # Port of the Cassandra server.
spring.data.cassandra.password= # Login password of the server.
spring.data.cassandra.pool.heartbeat-interval=30 # Heartbeat interval after which a message is sent on an idle connection to make sure it's still alive. If a duration suffix is not specified, seconds will be used.
spring.data.cassandra.pool.idle-timeout=120 # Idle timeout before an idle connection is removed. If a duration suffix is not specified, seconds will be used.
spring.data.cassandra.pool.max-queue-size=256 # Maximum number of requests that get queued if no connection is available.
spring.data.cassandra.pool.pool-timeout=5000ms # Pool timeout when trying to acquire a connection from a host's pool.
spring.data.cassandra.read-timeout= # Socket option: read time out.
spring.data.cassandra.reconnection-policy= # Reconnection policy class.
spring.data.cassandra.repositories.type=auto # Type of Cassandra repositories to enable.
spring.data.cassandra.retry-policy= # Class name of the retry policy.
spring.data.cassandra.serial-consistency-level= # Queries serial consistency level.
spring.data.cassandra.schema-action=none # Schema action to take at startup.
spring.data.cassandra.ssl=false # Enable SSL support.
spring.data.cassandra.username= # Login user of the server.
# DATA COUCHBASE (CouchbaseDataProperties)
spring.data.couchbase.auto-index=false # Automatically create views and indexes.
spring.data.couchbase.consistency=read-your-own-writes # Consistency to apply by default on generated queries.
spring.data.couchbase.repositories.type=auto # Type of Couchbase repositories to enable.
# ELASTICSEARCH (ElasticsearchProperties)
spring.data.elasticsearch.cluster-name=elasticsearch # Elasticsearch cluster name.
spring.data.elasticsearch.cluster-nodes= # Comma-separated list of cluster node addresses.
spring.data.elasticsearch.properties.*= # Additional properties used to configure the client.
spring.data.elasticsearch.repositories.enabled=true # Whether to enable Elasticsearch repositories.
# DATA LDAP
spring.data.ldap.repositories.enabled=true # Enable LDAP repositories.
# MONGODB (MongoProperties)
spring.data.mongodb.authentication-database= # Authentication database name.
spring.data.mongodb.database=test # Database name.
spring.data.mongodb.field-naming-strategy= # Fully qualified name of the FieldNamingStrategy to use.
spring.data.mongodb.grid-fs-database= # GridFS database name.
spring.data.mongodb.host=localhost # Mongo server host. Cannot be set with URI.
spring.data.mongodb.password= # Login password of the mongo server. Cannot be set with URI.
spring.data.mongodb.port=27017 # Mongo server port. Cannot be set with URI.
spring.data.mongodb.repositories.type=true # Type of Mongo repositories to enable.
spring.data.mongodb.uri=mongodb://localhost/test # Mongo database URI. Cannot be set with host, port and credentials.
spring.data.mongodb.username= # Login user of the mongo server. Cannot be set with URI.
# DATA REDIS
spring.data.redis.repositories.enabled=true # Whether to enable Redis repositories.
# NEO4J (Neo4jProperties)
spring.data.neo4j.auto-index=none # Auto index mode.
spring.data.neo4j.embedded.enabled=true # Whether to enable embedded mode if the embedded driver is available.
spring.data.neo4j.open-in-view=true # Register OpenSessionInViewInterceptor. Binds a Neo4j Session to the thread for the entire processing of the request.
spring.data.neo4j.password= # Login password of the server.
spring.data.neo4j.repositories.enabled=true # Whether to enable Neo4j repositories.
spring.data.neo4j.uri= # URI used by the driver. Auto-detected by default.
spring.data.neo4j.username= # Login user of the server.
# DATA REST (RepositoryRestProperties)
spring.data.rest.base-path= # Base path to be used by Spring Data REST to expose repository resources.
spring.data.rest.default-page-size= # Default size of pages.
spring.data.rest.detection-strategy=default # Strategy to use to determine which repositories get exposed.
spring.data.rest.enable-enum-translation= # Whether to enable enum value translation through the Spring Data REST default resource bundle.
spring.data.rest.limit-param-name= # Name of the URL query string parameter that indicates how many results to return at once.
spring.data.rest.max-page-size= # Maximum size of pages.
spring.data.rest.page-param-name= # Name of the URL query string parameter that indicates what page to return.
spring.data.rest.return-body-on-create= # Whether to return a response body after creating an entity.
spring.data.rest.return-body-on-update= # Whether to return a response body after updating an entity.
spring.data.rest.sort-param-name= # Name of the URL query string parameter that indicates what direction to sort results.
# SOLR (SolrProperties)
spring.data.solr.host=http://127.0.0.1:8983/solr # Solr host. Ignored if "zk-host" is set.
spring.data.solr.repositories.enabled=true # Whether to enable Solr repositories.
spring.data.solr.zk-host= # ZooKeeper host address in the form HOST:PORT.
# DATA WEB (SpringDataWebProperties)
spring.data.web.pageable.default-page-size=20 # Default page size.
spring.data.web.pageable.page-parameter=page # Page index parameter name.
spring.data.web.pageable.size-parameter=size # Page size parameter name.
spring.data.web.sort.sort-parameter=sort # Sort parameter name.
# DATASOURCE (DataSourceAutoConfiguration & DataSourceProperties)
spring.datasource.continue-on-error=false # Whether to stop if an error occurs while initializing the database.
spring.datasource.data= # Data (DML) script resource references.
spring.datasource.data-username= # Username of the database to execute DML scripts (if different).
spring.datasource.data-password= # Password of the database to execute DML scripts (if different).
spring.datasource.dbcp2.*= # Commons DBCP2 specific settings
spring.datasource.driver-class-name= # Fully qualified name of the JDBC driver. Auto-detected based on the URL by default.
spring.datasource.generate-unique-name=false # Whether to generate a random datasource name.
spring.datasource.hikari.*= # Hikari specific settings
spring.datasource.initialization-mode=embedded # Initialize the datasource with available DDL and DML scripts.
spring.datasource.jmx-enabled=false # Whether to enable JMX support (if provided by the underlying pool).
spring.datasource.jndi-name= # JNDI location of the datasource. Class, url, username & password are ignored when set.
spring.datasource.name=testdb # Name of the datasource.
spring.datasource.password= # Login password of the database.
spring.datasource.platform=all # Platform to use in the DDL or DML scripts (such as schema-${platform}.sql or data-${platform}.sql).
spring.datasource.schema= # Schema (DDL) script resource references.
spring.datasource.schema-username= # Username of the database to execute DDL scripts (if different).
spring.datasource.schema-password= # Password of the database to execute DDL scripts (if different).
spring.datasource.separator=; # Statement separator in SQL initialization scripts.
spring.datasource.sql-script-encoding= # SQL scripts encoding.
spring.datasource.tomcat.*= # Tomcat datasource specific settings
spring.datasource.type= # Fully qualified name of the connection pool implementation to use. By default, it is auto-detected from the classpath.
spring.datasource.url= # JDBC URL of the database.
spring.datasource.username= # Login username of the database.
spring.datasource.xa.data-source-class-name= # XA datasource fully qualified name.
spring.datasource.xa.properties= # Properties to pass to the XA data source.
# JEST (Elasticsearch HTTP client) (JestProperties)
spring.elasticsearch.jest.connection-timeout=3s # Connection timeout.
spring.elasticsearch.jest.multi-threaded=true # Whether to enable connection requests from multiple execution threads.
spring.elasticsearch.jest.password= # Login password.
spring.elasticsearch.jest.proxy.host= # Proxy host the HTTP client should use.
spring.elasticsearch.jest.proxy.port= # Proxy port the HTTP client should use.
spring.elasticsearch.jest.read-timeout=3s # Read timeout.
spring.elasticsearch.jest.uris=http://localhost:9200 # Comma-separated list of the Elasticsearch instances to use.
spring.elasticsearch.jest.username= # Login username.
# H2 Web Console (H2ConsoleProperties)
spring.h2.console.enabled=false # Whether to enable the console.
spring.h2.console.path=/h2-console # Path at which the console is available.
spring.h2.console.settings.trace=false # Whether to enable trace output.
spring.h2.console.settings.web-allow-others=false # Whether to enable remote access.
# InfluxDB (InfluxDbProperties)
spring.influx.password= # Login password.
spring.influx.url= # URL of the InfluxDB instance to which to connect.
spring.influx.user= # Login user.
# JOOQ (JooqAutoConfiguration)
spring.jooq.sql-dialect= # SQL dialect to use. Auto-detected by default.
# JDBC (JdbcProperties)
spring.jdbc.template.fetch-size=-1 # Number of rows that should be fetched from the database when more rows are needed.
spring.jdbc.template.max-rows=-1 # Maximum number of rows.
spring.jdbc.template.query-timeout= # Query timeout. If a duration suffix is not specified, seconds will be used.
# JPA (JpaBaseConfiguration, HibernateJpaAutoConfiguration)
spring.data.jpa.repositories.enabled=true # Whether to enable JPA repositories.
spring.jpa.database= # Target database to operate on, auto-detected by default. Can be alternatively set using the "databasePlatform" property.
spring.jpa.database-platform= # Name of the target database to operate on, auto-detected by default. Can be alternatively set using the "Database" enum.
spring.jpa.generate-ddl=false # Whether to initialize the schema on startup.
spring.jpa.hibernate.ddl-auto= # DDL mode. This is actually a shortcut for the "hibernate.hbm2ddl.auto" property. Defaults to "create-drop" when using an embedded database and no schema manager was detected. Otherwise, defaults to "none".
spring.jpa.hibernate.naming.implicit-strategy= # Hibernate 5 implicit naming strategy fully qualified name.
spring.jpa.hibernate.naming.physical-strategy= # Hibernate 5 physical naming strategy fully qualified name.
spring.jpa.hibernate.use-new-id-generator-mappings= # Whether to use Hibernate's newer IdentifierGenerator for AUTO, TABLE and SEQUENCE.
spring.jpa.mapping-resources= # Mapping resources (equivalent to "mapping-file" entries in persistence.xml).
spring.jpa.open-in-view=true # Register OpenEntityManagerInViewInterceptor. Binds a JPA EntityManager to the thread for the entire processing of the request.
spring.jpa.properties.*= # Additional native properties to set on the JPA provider.
spring.jpa.show-sql=false # Whether to enable logging of SQL statements.
# JTA (JtaAutoConfiguration)
spring.jta.enabled=true # Whether to enable JTA support.
spring.jta.log-dir= # Transaction logs directory.
spring.jta.transaction-manager-id= # Transaction manager unique identifier.
# ATOMIKOS (AtomikosProperties)
spring.jta.atomikos.connectionfactory.borrow-connection-timeout=30 # Timeout, in seconds, for borrowing connections from the pool.
spring.jta.atomikos.connectionfactory.ignore-session-transacted-flag=true # Whether to ignore the transacted flag when creating session.
spring.jta.atomikos.connectionfactory.local-transaction-mode=false # Whether local transactions are desired.
spring.jta.atomikos.connectionfactory.maintenance-interval=60 # The time, in seconds, between runs of the pool's maintenance thread.
spring.jta.atomikos.connectionfactory.max-idle-time=60 # The time, in seconds, after which connections are cleaned up from the pool.
spring.jta.atomikos.connectionfactory.max-lifetime=0 # The time, in seconds, that a connection can be pooled for before being destroyed. 0 denotes no limit.
spring.jta.atomikos.connectionfactory.max-pool-size=1 # The maximum size of the pool.
spring.jta.atomikos.connectionfactory.min-pool-size=1 # The minimum size of the pool.
spring.jta.atomikos.connectionfactory.reap-timeout=0 # The reap timeout, in seconds, for borrowed connections. 0 denotes no limit.
spring.jta.atomikos.connectionfactory.unique-resource-name=jmsConnectionFactory # The unique name used to identify the resource during recovery.
spring.jta.atomikos.datasource.borrow-connection-timeout=30 # Timeout, in seconds, for borrowing connections from the pool.
spring.jta.atomikos.datasource.default-isolation-level= # Default isolation level of connections provided by the pool.
spring.jta.atomikos.datasource.login-timeout= # Timeout, in seconds, for establishing a database connection.
spring.jta.atomikos.datasource.maintenance-interval=60 # The time, in seconds, between runs of the pool's maintenance thread.
spring.jta.atomikos.datasource.max-idle-time=60 # The time, in seconds, after which connections are cleaned up from the pool.
spring.jta.atomikos.datasource.max-lifetime=0 # The time, in seconds, that a connection can be pooled for before being destroyed. 0 denotes no limit.
spring.jta.atomikos.datasource.max-pool-size=1 # The maximum size of the pool.
spring.jta.atomikos.datasource.min-pool-size=1 # The minimum size of the pool.
spring.jta.atomikos.datasource.reap-timeout=0 # The reap timeout, in seconds, for borrowed connections. 0 denotes no limit.
spring.jta.atomikos.datasource.test-query= # SQL query or statement used to validate a connection before returning it.
spring.jta.atomikos.datasource.unique-resource-name=dataSource # The unique name used to identify the resource during recovery.
spring.jta.atomikos.properties.allow-sub-transactions=true # Specify whether sub-transactions are allowed.
spring.jta.atomikos.properties.checkpoint-interval=500 # Interval between checkpoints, in milliseconds.
spring.jta.atomikos.properties.default-jta-timeout=10000 # Default timeout for JTA transactions, in milliseconds.
spring.jta.atomikos.properties.enable-logging=true # Whether to enable disk logging.
spring.jta.atomikos.properties.force-shutdown-on-vm-exit=false # Whether a VM shutdown should trigger forced shutdown of the transaction core.
spring.jta.atomikos.properties.log-base-dir= # Directory in which the log files should be stored.
spring.jta.atomikos.properties.log-base-name=tmlog # Transactions log file base name.
spring.jta.atomikos.properties.max-actives=50 # Maximum number of active transactions.
spring.jta.atomikos.properties.max-timeout=30m # Maximum timeout that can be allowed for transactions.
spring.jta.atomikos.properties.recovery.delay=10000ms # Delay between two recovery scans.
spring.jta.atomikos.properties.recovery.forget-orphaned-log-entries-delay=86400000 # Delay after which recovery can cleanup pending ('orphaned') log entries.
spring.jta.atomikos.properties.recovery.max-retries=5 # Number of retry attempts to commit the transaction before throwing an exception.
spring.jta.atomikos.properties.recovery.retry-interval=10000ms # Delay between retry attempts.
spring.jta.atomikos.properties.serial-jta-transactions=true # Whether sub-transactions should be joined when possible.
spring.jta.atomikos.properties.service= # Transaction manager implementation that should be started.
spring.jta.atomikos.properties.threaded-two-phase-commit=false # Whether to use different (and concurrent) threads for two-phase commit on the participating resources.
spring.jta.atomikos.properties.transaction-manager-unique-name= # The transaction manager's unique name.
# BITRONIX
spring.jta.bitronix.connectionfactory.acquire-increment=1 # Number of connections to create when growing the pool.
spring.jta.bitronix.connectionfactory.acquisition-interval=1 # Time, in seconds, to wait before trying to acquire a connection again after an invalid connection was acquired.
spring.jta.bitronix.connectionfactory.acquisition-timeout=30 # Timeout, in seconds, for acquiring connections from the pool.
spring.jta.bitronix.connectionfactory.allow-local-transactions=true # Whether the transaction manager should allow mixing XA and non-XA transactions.
spring.jta.bitronix.connectionfactory.apply-transaction-timeout=false # Whether the transaction timeout should be set on the XAResource when it is enlisted.
spring.jta.bitronix.connectionfactory.automatic-enlisting-enabled=true # Whether resources should be enlisted and delisted automatically.
spring.jta.bitronix.connectionfactory.cache-producers-consumers=true # Whether producers and consumers should be cached.
spring.jta.bitronix.connectionfactory.defer-connection-release=true # Whether the provider can run many transactions on the same connection and supports transaction interleaving.
spring.jta.bitronix.connectionfactory.ignore-recovery-failures=false # Whether recovery failures should be ignored.
spring.jta.bitronix.connectionfactory.max-idle-time=60 # The time, in seconds, after which connections are cleaned up from the pool.
spring.jta.bitronix.connectionfactory.max-pool-size=10 # The maximum size of the pool. 0 denotes no limit.
spring.jta.bitronix.connectionfactory.min-pool-size=0 # The minimum size of the pool.
spring.jta.bitronix.connectionfactory.password= # The password to use to connect to the JMS provider.
spring.jta.bitronix.connectionfactory.share-transaction-connections=false #  Whether connections in the ACCESSIBLE state can be shared within the context of a transaction.
spring.jta.bitronix.connectionfactory.test-connections=true # Whether connections should be tested when acquired from the pool.
spring.jta.bitronix.connectionfactory.two-pc-ordering-position=1 # The position that this resource should take during two-phase commit (always first is Integer.MIN_VALUE, always last is Integer.MAX_VALUE).
spring.jta.bitronix.connectionfactory.unique-name=jmsConnectionFactory # The unique name used to identify the resource during recovery.
spring.jta.bitronix.connectionfactory.use-tm-join=true Whether TMJOIN should be used when starting XAResources.
spring.jta.bitronix.connectionfactory.user= # The user to use to connect to the JMS provider.
spring.jta.bitronix.datasource.acquire-increment=1 # Number of connections to create when growing the pool.
spring.jta.bitronix.datasource.acquisition-interval=1 # Time, in seconds, to wait before trying to acquire a connection again after an invalid connection was acquired.
spring.jta.bitronix.datasource.acquisition-timeout=30 # Timeout, in seconds, for acquiring connections from the pool.
spring.jta.bitronix.datasource.allow-local-transactions=true # Whether the transaction manager should allow mixing XA and non-XA transactions.
spring.jta.bitronix.datasource.apply-transaction-timeout=false # Whether the transaction timeout should be set on the XAResource when it is enlisted.
spring.jta.bitronix.datasource.automatic-enlisting-enabled=true # Whether resources should be enlisted and delisted automatically.
spring.jta.bitronix.datasource.cursor-holdability= # The default cursor holdability for connections.
spring.jta.bitronix.datasource.defer-connection-release=true # Whether the database can run many transactions on the same connection and supports transaction interleaving.
spring.jta.bitronix.datasource.enable-jdbc4-connection-test= # Whether Connection.isValid() is called when acquiring a connection from the pool.
spring.jta.bitronix.datasource.ignore-recovery-failures=false # Whether recovery failures should be ignored.
spring.jta.bitronix.datasource.isolation-level= # The default isolation level for connections.
spring.jta.bitronix.datasource.local-auto-commit= # The default auto-commit mode for local transactions.
spring.jta.bitronix.datasource.login-timeout= # Timeout, in seconds, for establishing a database connection.
spring.jta.bitronix.datasource.max-idle-time=60 # The time, in seconds, after which connections are cleaned up from the pool.
spring.jta.bitronix.datasource.max-pool-size=10 # The maximum size of the pool. 0 denotes no limit.
spring.jta.bitronix.datasource.min-pool-size=0 # The minimum size of the pool.
spring.jta.bitronix.datasource.prepared-statement-cache-size=0 # The target size of the prepared statement cache. 0 disables the cache.
spring.jta.bitronix.datasource.share-transaction-connections=false #  Whether connections in the ACCESSIBLE state can be shared within the context of a transaction.
spring.jta.bitronix.datasource.test-query= # SQL query or statement used to validate a connection before returning it.
spring.jta.bitronix.datasource.two-pc-ordering-position=1 # The position that this resource should take during two-phase commit (always first is Integer.MIN_VALUE, and always last is Integer.MAX_VALUE).
spring.jta.bitronix.datasource.unique-name=dataSource # The unique name used to identify the resource during recovery.
spring.jta.bitronix.datasource.use-tm-join=true Whether TMJOIN should be used when starting XAResources.
spring.jta.bitronix.properties.allow-multiple-lrc=false # Whether to allow multiple LRC resources to be enlisted into the same transaction.
spring.jta.bitronix.properties.asynchronous2-pc=false # Enable asynchronously execution of two phase commit.
spring.jta.bitronix.properties.background-recovery-interval-seconds=60 # Interval in seconds at which to run the recovery process in the background.
spring.jta.bitronix.properties.current-node-only-recovery=true # Whether to recover only the current node.
spring.jta.bitronix.properties.debug-zero-resource-transaction=false # Whether to log the creation and commit call stacks of transactions executed without a single enlisted resource.
spring.jta.bitronix.properties.default-transaction-timeout=60 # Default transaction timeout, in seconds.
spring.jta.bitronix.properties.disable-jmx=false # Whether to enable JMX support.
spring.jta.bitronix.properties.exception-analyzer= # Set the fully qualified name of the exception analyzer implementation to use.
spring.jta.bitronix.properties.filter-log-status=false # Whether to enable filtering of logs so that only mandatory logs are written.
spring.jta.bitronix.properties.force-batching-enabled=true #  Whether disk forces are batched.
spring.jta.bitronix.properties.forced-write-enabled=true # Whether logs are forced to disk.
spring.jta.bitronix.properties.graceful-shutdown-interval=60 # Maximum amount of seconds the TM waits for transactions to get done before aborting them at shutdown time.
spring.jta.bitronix.properties.jndi-transaction-synchronization-registry-name= # JNDI name of the TransactionSynchronizationRegistry.
spring.jta.bitronix.properties.jndi-user-transaction-name= # JNDI name of the UserTransaction.
spring.jta.bitronix.properties.journal=disk # Name of the journal. Can be 'disk', 'null', or a class name.
spring.jta.bitronix.properties.log-part1-filename=btm1.tlog # Name of the first fragment of the journal.
spring.jta.bitronix.properties.log-part2-filename=btm2.tlog # Name of the second fragment of the journal.
spring.jta.bitronix.properties.max-log-size-in-mb=2 # Maximum size in megabytes of the journal fragments.
spring.jta.bitronix.properties.resource-configuration-filename= # ResourceLoader configuration file name.
spring.jta.bitronix.properties.server-id= # ASCII ID that must uniquely identify this TM instance. Defaults to the machine's IP address.
spring.jta.bitronix.properties.skip-corrupted-logs=false # Skip corrupted transactions log entries.
spring.jta.bitronix.properties.warn-about-zero-resource-transaction=true # Whether to log a warning for transactions executed without a single enlisted resource.
# NARAYANA (NarayanaProperties)
spring.jta.narayana.default-timeout=60s # Transaction timeout. If a duration suffix is not specified, seconds will be used.
spring.jta.narayana.expiry-scanners=com.arjuna.ats.internal.arjuna.recovery.ExpiredTransactionStatusManagerScanner # Comma-separated list of expiry scanners.
spring.jta.narayana.log-dir= # Transaction object store directory.
spring.jta.narayana.one-phase-commit=true # Whether to enable one phase commit optimization.
spring.jta.narayana.periodic-recovery-period=120s # Interval in which periodic recovery scans are performed. If a duration suffix is not specified, seconds will be used.
spring.jta.narayana.recovery-backoff-period=10s # Back off period between first and second phases of the recovery scan. If a duration suffix is not specified, seconds will be used.
spring.jta.narayana.recovery-db-pass= # Database password to be used by the recovery manager.
spring.jta.narayana.recovery-db-user= # Database username to be used by the recovery manager.
spring.jta.narayana.recovery-jms-pass= # JMS password to be used by the recovery manager.
spring.jta.narayana.recovery-jms-user= # JMS username to be used by the recovery manager.
spring.jta.narayana.recovery-modules= # Comma-separated list of recovery modules.
spring.jta.narayana.transaction-manager-id=1 # Unique transaction manager id.
spring.jta.narayana.xa-resource-orphan-filters= # Comma-separated list of orphan filters.
# EMBEDDED MONGODB (EmbeddedMongoProperties)
spring.mongodb.embedded.features=SYNC_DELAY # Comma-separated list of features to enable.
spring.mongodb.embedded.storage.database-dir= # Directory used for data storage.
spring.mongodb.embedded.storage.oplog-size= # Maximum size of the oplog, in megabytes.
spring.mongodb.embedded.storage.repl-set-name= # Name of the replica set.
spring.mongodb.embedded.version=2.6.10 # Version of Mongo to use.
# REDIS (RedisProperties)
spring.redis.cluster.max-redirects= # Maximum number of redirects to follow when executing commands across the cluster.
spring.redis.cluster.nodes= # Comma-separated list of "host:port" pairs to bootstrap from.
spring.redis.database=0 # Database index used by the connection factory.
spring.redis.url= # Connection URL. Overrides host, port, and password. User is ignored. Example: redis://user:[email protected]:6379
spring.redis.host=localhost # Redis server host.
spring.redis.jedis.pool.max-active=8 # Max number of connections that can be allocated by the pool at a given time. Use a negative value for no limit.
spring.redis.jedis.pool.max-idle=8 # Max number of "idle" connections in the pool. Use a negative value to indicate an unlimited number of idle connections.
spring.redis.jedis.pool.max-wait=-1ms # Maximum amount of time a connection allocation should block before throwing an exception when the pool is exhausted. Use a negative value to block indefinitely.
spring.redis.jedis.pool.min-idle=0 # Target for the minimum number of idle connections to maintain in the pool. This setting only has an effect if it is positive.
spring.redis.lettuce.pool.max-active=8 # Maximum number of connections that can be allocated by the pool at a given time. Use a negative value for no limit.
spring.redis.lettuce.pool.max-idle=8 # Maximum number of "idle" connections in the pool. Use a negative value to indicate an unlimited number of idle connections.
spring.redis.lettuce.pool.max-wait=-1ms # Maximum amount of time a connection allocation should block before throwing an exception when the pool is exhausted. Use a negative value to block indefinitely.
spring.redis.lettuce.pool.min-idle=0 # Target for the minimum number of idle connections to maintain in the pool. This setting only has an effect if it is positive.
spring.redis.lettuce.shutdown-timeout=100ms # Shutdown timeout.
spring.redis.password= # Login password of the redis server.
spring.redis.port=6379 # Redis server port.
spring.redis.sentinel.master= # Name of the Redis server.
spring.redis.sentinel.nodes= # Comma-separated list of "host:port" pairs.
spring.redis.ssl=false # Whether to enable SSL support.
spring.redis.timeout=0 # Connection timeout.
# TRANSACTION (TransactionProperties)
spring.transaction.default-timeout= # Default transaction timeout. If a duration suffix is not specified, seconds will be used.
spring.transaction.rollback-on-commit-failure= # Whether to roll back on commit failures.
# ----------------------------------------
# INTEGRATION PROPERTIES
# ----------------------------------------
# ACTIVEMQ (ActiveMQProperties)
spring.activemq.broker-url= # URL of the ActiveMQ broker. Auto-generated by default.
spring.activemq.close-timeout=15s # Time to wait before considering a close complete.
spring.activemq.in-memory=true # Whether the default broker URL should be in memory. Ignored if an explicit broker has been specified.
spring.activemq.non-blocking-redelivery=false # Whether to stop message delivery before re-delivering messages from a rolled back transaction. This implies that message order is not preserved when this is enabled.
spring.activemq.password= # Login password of the broker.
spring.activemq.send-timeout=0 # Time to wait on message sends for a response. Set it to 0 to wait forever.
spring.activemq.user= # Login user of the broker.
spring.activemq.packages.trust-all= # Whether to trust all packages.
spring.activemq.packages.trusted= # Comma-separated list of specific packages to trust (when not trusting all packages).
spring.activemq.pool.block-if-full=true # Whether to block when a connection is requested and the pool is full. Set it to false to throw a "JMSException" instead.
spring.activemq.pool.block-if-full-timeout=-1ms # Blocking period before throwing an exception if the pool is still full.
spring.activemq.pool.create-connection-on-startup=true # Whether to create a connection on startup. Can be used to warm up the pool on startup.
spring.activemq.pool.enabled=false # Whether a PooledConnectionFactory should be created, instead of a regular ConnectionFactory.
spring.activemq.pool.expiry-timeout=0ms # Connection expiration timeout.
spring.activemq.pool.idle-timeout=30s # Connection idle timeout.
spring.activemq.pool.max-connections=1 # Maximum number of pooled connections.
spring.activemq.pool.maximum-active-session-per-connection=500 # Maximum number of active sessions per connection.
spring.activemq.pool.reconnect-on-exception=true # Reset the connection when a "JMSException" occurs.
spring.activemq.pool.time-between-expiration-check=-1ms # Time to sleep between runs of the idle connection eviction thread. When negative, no idle connection eviction thread runs.
spring.activemq.pool.use-anonymous-producers=true # Whether to use only one anonymous "MessageProducer" instance. Set it to false to create one "MessageProducer" every time one is required.
# ARTEMIS (ArtemisProperties)
spring.artemis.embedded.cluster-password= # Cluster password. Randomly generated on startup by default.
spring.artemis.embedded.data-directory= # Journal file directory. Not necessary if persistence is turned off.
spring.artemis.embedded.enabled=true # Whether to enable embedded mode if the Artemis server APIs are available.
spring.artemis.embedded.persistent=false # Whether to enable persistent store.
spring.artemis.embedded.queues= # Comma-separated list of queues to create on startup.
spring.artemis.embedded.server-id= # Server ID. By default, an auto-incremented counter is used.
spring.artemis.embedded.topics= # Comma-separated list of topics to create on startup.
spring.artemis.host=localhost # Artemis broker host.
spring.artemis.mode= # Artemis deployment mode, auto-detected by default.
spring.artemis.password= # Login password of the broker.
spring.artemis.port=61616 # Artemis broker port.
spring.artemis.user= # Login user of the broker.
# SPRING BATCH (BatchProperties)
spring.batch.initialize-schema=embedded # Database schema initialization mode.
spring.batch.job.enabled=true # Execute all Spring Batch jobs in the context on startup.
spring.batch.job.names= # Comma-separated list of job names to execute on startup (for instance, `job1,job2`). By default, all Jobs found in the context are executed.
spring.batch.schema=classpath:org/springframework/batch/core/schema-@@platform@@.sql # Path to the SQL file to use to initialize the database schema.
spring.batch.table-prefix= # Table prefix for all the batch meta-data tables.
# SPRING INTEGRATION (IntegrationProperties)
spring.integration.jdbc.initialize-schema=embedded # Database schema initialization mode.
spring.integration.jdbc.schema=classpath:org/springframework/integration/jdbc/schema-@@platform@@.sql # Path to the SQL file to use to initialize the database schema.
# JMS (JmsProperties)
spring.jms.jndi-name= # Connection factory JNDI name. When set, takes precedence to others connection factory auto-configurations.
spring.jms.listener.acknowledge-mode= # Acknowledge mode of the container. By default, the listener is transacted with automatic acknowledgment.
spring.jms.listener.auto-startup=true # Start the container automatically on startup.
spring.jms.listener.concurrency= # Minimum number of concurrent consumers.
spring.jms.listener.max-concurrency= # Maximum number of concurrent consumers.
spring.jms.pub-sub-domain=false # Whether the default destination type is topic.
spring.jms.template.default-destination= # Default destination to use on send and receive operations that do not have a destination parameter.
spring.jms.template.delivery-delay= # Delivery delay to use for send calls.
spring.jms.template.delivery-mode= # Delivery mode. Enables QoS (Quality of Service) when set.
spring.jms.template.priority= # Priority of a message when sending. Enables QoS (Quality of Service) when set.
spring.jms.template.qos-enabled= # Whether to enable explicit QoS (Quality of Service) when sending a message.
spring.jms.template.receive-timeout= # Timeout to use for receive calls.
spring.jms.template.time-to-live= # Time-to-live of a message when sending. Enable QoS (Quality of Service) when set.
# APACHE KAFKA (KafkaProperties)
spring.kafka.admin.client-id= # ID to pass to the server when making requests. Used for server-side logging.
spring.kafka.admin.fail-fast=false # Whether to fail fast if the broker is not available on startup.
spring.kafka.admin.properties.*= # Additional admin-specific properties used to configure the client.
spring.kafka.admin.ssl.key-password= # Password of the private key in the key store file.
spring.kafka.admin.ssl.keystore-location= # Location of the key store file.
spring.kafka.admin.ssl.keystore-password= # Password of the key store file.
spring.kafka.admin.ssl.truststore-location= # Location of the trust store file.
spring.kafka.admin.ssl.truststore-password= # Store password for the trust store file.
spring.kafka.bootstrap-servers= # Comma-delimited list of host:port pairs to use for establishing the initial connection to the Kafka cluster.
spring.kafka.client-id= # ID to pass to the server when making requests. Used for server-side logging.
spring.kafka.consumer.auto-commit-interval= # Frequency with which the consumer offsets are auto-committed to Kafka if 'enable.auto.commit' is set to true.
spring.kafka.consumer.auto-offset-reset= # What to do when there is no initial offset in Kafka or if the current offset no longer exists on the server.
spring.kafka.consumer.bootstrap-servers= # Comma-delimited list of host:port pairs to use for establishing the initial connection to the Kafka cluster.
spring.kafka.consumer.client-id= # ID to pass to the server when making requests. Used for server-side logging.
spring.kafka.consumer.enable-auto-commit= # Whether the consumer's offset is periodically committed in the background.
spring.kafka.consumer.fetch-max-wait= # Maximum amount of time the server blocks before answering the fetch request if there isn't sufficient data to immediately satisfy the requirement given by "fetch.min.bytes".
spring.kafka.consumer.fetch-min-size= # Minimum amount of data, in bytes, the server should return for a fetch request.
spring.kafka.consumer.group-id= # Unique string that identifies the consumer group to which this consumer belongs.
spring.kafka.consumer.heartbeat-interval= # Expected time between heartbeats to the consumer coordinator.
spring.kafka.consumer.key-deserializer= # Deserializer class for keys.
spring.kafka.consumer.max-poll-records= # Maximum number of records returned in a single call to poll().
spring.kafka.consumer.properties.*= # Additional consumer-specific properties used to configure the client.
spring.kafka.consumer.ssl.key-password= # Password of the private key in the key store file.
spring.kafka.consumer.ssl.keystore-location= # Location of the key store file.
spring.kafka.consumer.ssl.keystore-password= # Store password for the key store file.
spring.kafka.consumer.ssl.truststore-location= # Location of the trust store file.
spring.kafka.consumer.ssl.truststore-password= # Store password for the trust store file.
spring.kafka.consumer.value-deserializer= # Deserializer class for values.
spring.kafka.jaas.control-flag=required # Control flag for login configuration.
spring.kafka.jaas.enabled= # Whether to enable JAAS configuration.
spring.kafka.jaas.login-module=com.sun.security.auth.module.Krb5LoginModule # Login module.
spring.kafka.jaas.options= # Additional JAAS options.
spring.kafka.listener.ack-count= # Number of records between offset commits when ackMode is "COUNT" or "COUNT_TIME".
spring.kafka.listener.ack-mode= # Listener AckMode. See the spring-kafka documentation.
spring.kafka.listener.ack-time= # Time between offset commits when ackMode is "TIME" or "COUNT_TIME".
spring.kafka.listener.concurrency= # Number of threads to run in the listener containers.
spring.kafka.listener.poll-timeout= # Timeout to use when polling the consumer.
spring.kafka.listener.type=single # Listener type.
spring.kafka.producer.acks= # Number of acknowledgments the producer requires the leader to have received before considering a request complete.
spring.kafka.producer.batch-size= # Number of records to batch before sending.
spring.kafka.producer.bootstrap-servers= # Comma-delimited list of host:port pairs to use for establishing the initial connection to the Kafka cluster.
spring.kafka.producer.buffer-memory= # Total bytes of memory the producer can use to buffer records waiting to be sent to the server.
spring.kafka.producer.client-id= # ID to pass to the server when making requests. Used for server-side logging.
spring.kafka.producer.compression-type= # Compression type for all data generated by the producer.
spring.kafka.producer.key-serializer= # Serializer class for keys.
spring.kafka.producer.properties.*= # Additional producer-specific properties used to configure the client.
spring.kafka.producer.retries= # When greater than zero, enables retrying of failed sends.
spring.kafka.producer.ssl.key-password= # Password of the private key in the key store file.
spring.kafka.producer.ssl.keystore-location= # Location of the key store file.
spring.kafka.producer.ssl.keystore-password= # Store password for the key store file.
spring.kafka.producer.ssl.truststore-location= # Location of the trust store file.
spring.kafka.producer.ssl.truststore-password= # Store password for the trust store file.
spring.kafka.producer.transaction-id-prefix= # When non empty, enables transaction support for producer.
spring.kafka.producer.value-serializer= # Serializer class for values.
spring.kafka.properties.*= # Additional properties, common to producers and consumers, used to configure the client.
spring.kafka.ssl.key-password= # Password of the private key in the key store file.
spring.kafka.ssl.keystore-location= # Location of the key store file.
spring.kafka.ssl.keystore-password= # Store password for the key store file.
spring.kafka.ssl.truststore-location= # Location of the trust store file.
spring.kafka.ssl.truststore-password= # Store password for the trust store file.
spring.kafka.template.default-topic= # Default topic to which messages are sent.
# RABBIT (RabbitProperties)
spring.rabbitmq.addresses= # Comma-separated list of addresses to which the client should connect.
spring.rabbitmq.cache.channel.checkout-timeout= # Duration to wait to obtain a channel if the cache size has been reached.
spring.rabbitmq.cache.channel.size= # Number of channels to retain in the cache.
spring.rabbitmq.cache.connection.mode=channel # Connection factory cache mode.
spring.rabbitmq.cache.connection.size= # Number of connections to cache.
spring.rabbitmq.connection-timeout= # Connection timeout. Set it to zero to wait forever.
spring.rabbitmq.dynamic=true # Whether to create an AmqpAdmin bean.
spring.rabbitmq.host=localhost # RabbitMQ host.
spring.rabbitmq.listener.direct.acknowledge-mode= # Acknowledge mode of container.
spring.rabbitmq.listener.direct.auto-startup=true # Whether to start the container automatically on startup.
spring.rabbitmq.listener.direct.consumers-per-queue= # Number of consumers per queue.
spring.rabbitmq.listener.direct.default-requeue-rejected= # Whether rejected deliveries are re-queued by default. Defaults to true.
spring.rabbitmq.listener.direct.idle-event-interval= # How often idle container events should be published.
spring.rabbitmq.listener.direct.prefetch= # Number of messages to be handled in a single request. It should be greater than or equal to the transaction size (if used).
spring.rabbitmq.listener.direct.retry.enabled=false # Whether publishing retries are enabled.
spring.rabbitmq.listener.direct.retry.initial-interval=1000ms # Interval between the first and second attempt to publish or deliver a message.
spring.rabbitmq.listener.direct.retry.max-attempts=3 # Maximum number of attempts to publish or deliver a message.
spring.rabbitmq.listener.direct.retry.max-interval=10000ms # Maximum interval between attempts.
spring.rabbitmq.listener.direct.retry.multiplier=1 # Multiplier to apply to the previous retry interval.
spring.rabbitmq.listener.direct.retry.stateless=true # Whether retries are stateless or stateful.
spring.rabbitmq.listener.simple.acknowledge-mode= # Acknowledge mode of container.
spring.rabbitmq.listener.simple.auto-startup=true # Whether to start the container automatically on startup.
spring.rabbitmq.listener.simple.concurrency= # Minimum number of listener invoker threads.
spring.rabbitmq.listener.simple.default-requeue-rejected= # Whether to re-queue delivery failures.
spring.rabbitmq.listener.simple.idle-event-interval= # How often idle container events should be published.
spring.rabbitmq.listener.simple.max-concurrency= # Maximum number of listener invoker.
spring.rabbitmq.listener.simple.prefetch= # Number of messages to be handled in a single request. It should be greater than or equal to the transaction size (if used).
spring.rabbitmq.listener.simple.retry.enabled=false # Whether publishing retries are enabled.
spring.rabbitmq.listener.simple.retry.initial-interval=1000 # Interval, in milliseconds, between the first and second attempt to deliver a message.
spring.rabbitmq.listener.simple.retry.max-attempts=3 # Maximum number of attempts to deliver a message.
spring.rabbitmq.listener.simple.retry.max-interval=10000 # Maximum interval, in milliseconds, between attempts.
spring.rabbitmq.listener.simple.retry.multiplier=1.0 # Multiplier to apply to the previous delivery retry interval.
spring.rabbitmq.listener.simple.retry.stateless=true # Whether or not retry is stateless or stateful.
spring.rabbitmq.listener.simple.transaction-size= # Number of messages to be processed in a transaction. That is, the number of messages between acks. For best results, it should be less than or equal to the prefetch count.
spring.rabbitmq.listener.type=simple # Listener container type.
spring.rabbitmq.password= # Login to authenticate against the broker.
spring.rabbitmq.port=5672 # RabbitMQ port.
spring.rabbitmq.publisher-confirms=false # Whether to enable publisher confirms.
spring.rabbitmq.publisher-returns=false # Whether to enable publisher returns.
spring.rabbitmq.requested-heartbeat= # Requested heartbeat timeout; zero for none. If a duration suffix is not specified, seconds will be used.
spring.rabbitmq.ssl.enabled=false # Whether to enable SSL support.
spring.rabbitmq.ssl.key-store= # Path to the key store that holds the SSL certificate.
spring.rabbitmq.ssl.key-store-password= # Password used to access the key store.
spring.rabbitmq.ssl.key-store-type=PKCS12 # Key store type.
spring.rabbitmq.ssl.trust-store= # Trust store that holds SSL certificates.
spring.rabbitmq.ssl.trust-store-password= # Password used to access the trust store.
spring.rabbitmq.ssl.trust-store-type=JKS # Trust store type.
spring.rabbitmq.ssl.algorithm= # SSL algorithm to use. By default, configured by the Rabbit client library.
spring.rabbitmq.template.mandatory=false # Whether to enable mandatory messages.
spring.rabbitmq.template.receive-timeout=0 # Timeout for `receive()` methods.
spring.rabbitmq.template.reply-timeout=5000 # Timeout for `sendAndReceive()` methods.
spring.rabbitmq.template.retry.enabled=false # Whether to enable retries in the `RabbitTemplate`.
spring.rabbitmq.template.retry.initial-interval=1000 # Interval, in milliseconds, between the first and second attempt to publish a message.
spring.rabbitmq.template.retry.max-attempts=3 # Maximum number of attempts to publish a message.
spring.rabbitmq.template.retry.max-interval=10000 # Maximum number of attempts to publish a message.
spring.rabbitmq.template.retry.multiplier=1.0 # Multiplier to apply to the previous publishing retry interval.
spring.rabbitmq.username= # Login user to authenticate to the broker.
spring.rabbitmq.virtual-host= # Virtual host to use when connecting to the broker.
# ----------------------------------------
# ACTUATOR PROPERTIES
# ----------------------------------------
# MANAGEMENT HTTP SERVER (ManagementServerProperties)
management.server.add-application-context-header=false # Add the "X-Application-Context" HTTP header in each response. Requires a custom management.server.port.
management.server.address= # Network address that to which the management endpoints should bind. Requires a custom management.server.port.
management.server.context-path= # Management endpoint context-path. For instance, `/actuator`. Requires a custom management.server.port
management.server.port= # Management endpoint HTTP port. Uses the same port as the application by default. Configure a different port to use management-specific SSL.
management.server.ssl.ciphers= # Supported SSL ciphers. Requires a custom management.port.
management.server.ssl.client-auth= # Whether client authentication is wanted ("want") or needed ("need"). Requires a trust store. Requires a custom management.server.port.
management.server.ssl.enabled= # Whether to enable SSL support. Requires a custom management.server.port.
management.server.ssl.enabled-protocols= # Enabled SSL protocols. Requires a custom management.server.port.
management.server.ssl.key-alias= # Alias that identifies the key in the key store. Requires a custom management.server.port.
management.server.ssl.key-password= # Password used to access the key in the key store. Requires a custom management.server.port.
management.server.ssl.key-store= # Path to the key store that holds the SSL certificate (typically a jks file). Requires a custom management.server.port.
management.server.ssl.key-store-password= # Password used to access the key store. Requires a custom management.server.port.
management.server.ssl.key-store-provider= # Provider for the key store. Requires a custom management.server.port.
management.server.ssl.key-store-type= # Type of the key store. Requires a custom management.server.port.
management.server.ssl.protocol=TLS # SSL protocol to use. Requires a custom management.server.port.
management.server.ssl.trust-store= # Trust store that holds SSL certificates. Requires a custom management.server.port.
management.server.ssl.trust-store-password= # Password used to access the trust store. Requires a custom management.server.port.
management.server.ssl.trust-store-provider= # Provider for the trust store. Requires a custom management.server.port.
management.server.ssl.trust-store-type= # Type of the trust store. Requires a custom management.server.port.
# CLOUDFOUNDRY
management.cloudfoundry.enabled=true # Whether to enable extended Cloud Foundry actuator endpoints.
management.cloudfoundry.skip-ssl-validation=false # Whether to skip SSL verification for Cloud Foundry actuator endpoint security calls.
# ENDPOINTS GENERAL CONFIGURATION
management.endpoints.enabled-by-default= # Enable or disable all endpoints by default.
# ENDPOINTS JMX CONFIGURATION (JmxEndpointProperties)
management.endpoints.jmx.enabled=true # Whether JMX endpoints are enabled.
management.endpoints.jmx.expose=* # Endpoint IDs that should be exposed or '*' for all.
management.endpoints.jmx.exclude= # Endpoint IDs that should be excluded.
management.endpoints.jmx.domain=org.springframework.boot # Endpoints JMX domain name. Fallback to 'spring.jmx.default-domain' if set.
management.endpoints.jmx.static-names=false # Additional static properties to append to all ObjectNames of MBeans representing Endpoints.
management.endpoints.jmx.unique-names=false # Whether to ensure that ObjectNames are modified in case of conflict.
# ENDPOINTS WEB CONFIGURATION (WebEndpointProperties)
management.endpoints.web.enabled=true # Whether web endpoints are enabled
management.endpoints.web.expose=info,status # Endpoint IDs that should be exposed or '*' for all.
management.endpoints.web.exclude= # Endpoint IDs that should be excluded.
management.endpoints.web.base-path=/actuator # Base path for Web endpoints. Relative to server.context-path or management.server.context-path if management.server.port is configured.
management.endpoints.web.path-mapping= # Mapping between endpoint IDs and the path that should expose them.
# ENDPOINTS CORS CONFIGURATION (CorsEndpointProperties)
management.endpoints.web.cors.allow-credentials= # Whether credentials are supported. When not set, credentials are not supported.
management.endpoints.web.cors.allowed-headers= # Comma-separated list of headers to allow in a request. '*' allows all headers.
management.endpoints.web.cors.allowed-methods= # Comma-separated list of methods to allow. '*' allows all methods. When not set, defaults to GET.
management.endpoints.web.cors.allowed-origins= # Comma-separated list of origins to allow. '*' allows all origins. When not set, CORS support is disabled.
management.endpoints.web.cors.exposed-headers= # Comma-separated list of headers to include in a response.
management.endpoints.web.cors.max-age=1800 # How long the response from a pre-flight request can be cached by clients. If a duration suffix is not specified, seconds will be used.
# AUDIT EVENTS ENDPOINT (AuditEventsEndpoint)
management.endpoint.auditevents.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.auditevents.enabled= # Whether to enable the auditevents endpoint.
# BEANS ENDPOINT (BeansEndpoint)
management.endpoint.beans.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.beans.enabled= # Whether to enable the beans endpoint.
# CONDITIONS REPORT ENDPOINT (ConditionsReportEndpoint)
management.endpoint.conditions.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.conditions.enabled= # Whether to enable the conditions endpoint.
# CONFIGURATION PROPERTIES REPORT ENDPOINT (ConfigurationPropertiesReportEndpoint)
management.endpoint.configprops.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.configprops.enabled= # Whether to enable the configprops endpoint.
management.endpoint.configprops.keys-to-sanitize=password,secret,key,token,.*credentials.*,vcap_services # Keys that should be sanitized. Keys can be simple strings that the property ends with or regular expressions.
# ENVIRONMENT ENDPOINT  (EnvironmentEndpoint)
management.endpoint.env.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.env.enabled= # Whether to enable the env endpoint.
management.endpoint.env.keys-to-sanitize=password,secret,key,token,.*credentials.*,vcap_services # Keys that should be sanitized. Keys can be simple strings that the property ends with or regular expressions.
# FLYWAY ENDPOINT (FlywayEndpoint)
management.endpoint.flyway.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.flyway.enabled= # Whether to enable the flyway endpoint.
# HEALTH ENDPOINT (HealthEndpoint)
management.endpoint.health.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.health.enabled= # Whether to enable the health endpoint.
management.endpoint.health.show-details= # Whether to show full health details
# HEAP DUMP ENDPOINT (HeapDumpWebEndpoint)
management.endpoint.heapdump.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.heapdump.enabled= # Whether to enable the heapdump endpoint.
# INFO ENDPOINT (InfoEndpoint)
management.endpoint.info.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.info.enabled=true # Whether to enable the info endpoint.
# LIQUIBASE ENDPOINT (LiquibaseEndpoint)
management.endpoint.liquibase.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.liquibase.enabled= # Whether to enable the liquibase endpoint.
# LOG FILE ENDPOINT (LogFileWebEndpoint)
management.endpoint.logfile.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.logfile.enabled= # Whether to enable the logfile endpoint.
management.endpoint.logfile.external-file= # External Logfile to be accessed. Can be used if the logfile is written by output redirect and not by the logging system itself.
# LOGGERS ENDPOINT (LoggersEndpoint)
management.endpoint.loggers.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.loggers.enabled= # Whether to enable the loggers endpoint.
# REQUEST MAPPING ENDPOINT  (RequestMappingEndpoint)
management.endpoint.mappings.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.mappings.enabled= # Whether to enable the mappings endpoint.
# METRICS ENDPOINT (MetricsEndpoint)
management.endpoint.metrics.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.metrics.enabled= # Whether to enable the metrics endpoint.
# PROMETHEUS ENDPOINT (PrometheusScrapeEndpoint)
management.endpoint.prometheus.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.prometheus.enabled= # Whether to enable the metrics endpoint.
# SCHEDULED TASKS ENDPOINT (ScheduledTasksEndpoint)
management.endpoint.scheduledtasks.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.scheduledtasks.enabled= # Whether to enable the scheduled tasks endpoint.
# SESSIONS ENDPOINT (SessionsEndpoint)
management.endpoint.sessions.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.sessions.enabled= # Whether to enable the sessions endpoint.
# SHUTDOWN ENDPOINT (ShutdownEndpoint)
management.endpoint.shutdown.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.shutdown.enabled=false # Whether to enable the shutdown endpoint.
# THREAD DUMP ENDPOINT (ThreadDumpEndpoint)
management.endpoint.threaddump.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.threaddump.enabled= # Whether to enable the threaddump endpoint.
# TRACE ENDPOINT (TraceEndpoint)
management.endpoint.trace.cache.time-to-live=0ms # Maximum time that a response can be cached.
management.endpoint.trace.enabled= # Whether to enable the trace endpoint.
# HEALTH INDICATORS
management.health.db.enabled=true # Whether to enable database health check.
management.health.cassandra.enabled=true # Whether to enable Cassandra health check.
management.health.couchbase.enabled=true # Whether to enable Couchbase health check.
management.health.defaults.enabled=true # Whether to enable default health indicators.
management.health.diskspace.enabled=true # Whether to enable disk space health check.
management.health.diskspace.path= # Path used to compute the available disk space.
management.health.diskspace.threshold=0 # Minimum disk space, in bytes, that should be available.
management.health.elasticsearch.enabled=true # Whether to enable Elasticsearch health check.
management.health.elasticsearch.indices= # Comma-separated index names.
management.health.elasticsearch.response-timeout=100ms # The time to wait for a response from the cluster.
management.health.jms.enabled=true # Whether to enable JMS health check.
management.health.ldap.enabled=true # Whether to enable LDAP health check.
management.health.mail.enabled=true # Whether to enable Mail health check.
management.health.mongo.enabled=true # Whether to enable MongoDB health check.
management.health.neo4j.enabled=true # Whether to enable Neo4j health check.
management.health.rabbit.enabled=true # Whether to enable RabbitMQ health check.
management.health.redis.enabled=true # Whether to enable Redis health check.
management.health.solr.enabled=true # Whether to enable Solr health check.
management.health.status.http-mapping= # Mapping of health statuses to HTTP status codes. By default, registered health statuses map to sensible defaults (for example, UP maps to 200).
management.health.status.order=DOWN, OUT_OF_SERVICE, UP, UNKNOWN # Comma-separated list of health statuses in order of severity.
# INFO CONTRIBUTORS (InfoContributorProperties)
management.info.build.enabled=true # Whether to enable build info.
management.info.defaults.enabled=true # Whether to enable default info contributors.
management.info.env.enabled=true # Whether to enable environment info.
management.info.git.enabled=true # Whether to enable git info.
management.info.git.mode=simple # Mode to use to expose git information.
# JOLOKIA (JolokiaProperties)
management.jolokia.config.*= # Jolokia settings. See the Jolokia manual for details.
management.jolokia.enabled=false # Whether to enable Jolokia.
management.jolokia.path=/jolokia # Path at which Jolokia is available.
# TRACING (TraceEndpointProperties)
management.trace.filter.enabled=true # Whether to enable the trace servlet filter.
management.trace.include=request-headers,response-headers,cookies,errors # Items to be included in the trace.
# METRICS
spring.metrics.use-global-registry=true # Whether auto-configured MeterRegistry implementations should be bound to the global static registry on Metrics.
spring.metrics.export.atlas.batch-size= # Number of measurements per request to use for the backend. If more measurements are found, then multiple requests will be made.
spring.metrics.export.atlas.config-refresh-frequency= # Frequency for refreshing config settings from the LWC service.
spring.metrics.export.atlas.config-time-to-live= # Time to live for subscriptions from the LWC service.
spring.metrics.export.atlas.config-uri= # URI for the Atlas LWC endpoint to retrieve current subscriptions.
spring.metrics.export.atlas.connect-timeout= # Connection timeout for requests to the backend.
spring.metrics.export.atlas.enabled= # Whether exporting of metrics to this backend is enabled.
spring.metrics.export.atlas.eval-uri= # URI for the Atlas LWC endpoint to evaluate the data for a subscription.
spring.metrics.export.atlas.lwc-enabled= # Enable streaming to Atlas LWC.
spring.metrics.export.atlas.meter-time-to-live= # Time to live for meters that do not have any activity. After this period the meter will be considered expired and will not get reported.
spring.metrics.export.atlas.num-threads= # Number of threads to use with the metrics publishing scheduler.
spring.metrics.export.atlas.read-timeout= # Read timeout for requests to the backend.
spring.metrics.export.atlas.step=1m # Step size (i.e. reporting frequency) to use.
spring.metrics.export.atlas.uri= # URI of the Atlas server.
spring.metrics.export.datadog.api-key= # Datadog API key.
spring.metrics.export.datadog.batch-size= # Number of measurements per request to use for the backend. If more measurements are found, then multiple requests will be made.
spring.metrics.export.datadog.connect-timeout= # Connection timeout for requests to the backend.
spring.metrics.export.datadog.enabled= # Whether exporting of metrics to this backend is enabled.
spring.metrics.export.datadog.host-tag= # Tag that will be mapped to "host" when shipping metrics to Datadog. Can be omitted if host should be omitted on publishing.
spring.metrics.export.datadog.num-threads= # Number of threads to use with the metrics publishing scheduler.
spring.metrics.export.datadog.read-timeout= # Read timeout for requests to the backend.
spring.metrics.export.datadog.step=1m # Step size (i.e. reporting frequency) to use.
spring.metrics.export.datadog.uri= # URI to ship metrics to. If you need to publish metrics to an internal proxy en-route to Datadog, you can define the location of the proxy with this.
spring.metrics.export.ganglia.addressing-mode= # UDP addressing mode, either unicast or multicast.
spring.metrics.export.ganglia.duration-units= # Base time unit used to report durations.
spring.metrics.export.ganglia.enabled= # Whether exporting of metrics to Ganglia is enabled.
spring.metrics.export.ganglia.host= # Host of the Ganglia server to receive exported metrics.
spring.metrics.export.ganglia.port= # Port of the Ganglia server to receive exported metrics.
spring.metrics.export.ganglia.protocol-version= # Ganglia protocol version. Must be either 3.1 or 3.0.
spring.metrics.export.ganglia.rate-units= # Base time unit used to report rates.
spring.metrics.export.ganglia.step= # Step size (i.e. reporting frequency) to use.
spring.metrics.export.ganglia.time-to-live= # Time to live for metrics on Ganglia.
spring.metrics.export.graphite.duration-units= # Base time unit used to report durations.
spring.metrics.export.graphite.enabled= # Whether exporting of metrics to Graphite is enabled.
spring.metrics.export.graphite.host= # Host of the Graphite server to receive exported metrics.
spring.metrics.export.graphite.port= # Port of the Graphite server to receive exported metrics.
spring.metrics.export.graphite.protocol= # Protocol to use while shipping data to Graphite.
spring.metrics.export.graphite.rate-units= # Base time unit used to report rates.
spring.metrics.export.graphite.step= # Step size (i.e. reporting frequency) to use.
spring.metrics.export.influx.batch-size= # Number of measurements per request to use for the backend. If more measurements are found, then multiple requests will be made.
spring.metrics.export.influx.compressed= # Enable GZIP compression of metrics batches published to Influx.
spring.metrics.export.influx.connect-timeout= # Connection timeout for requests to the backend.
spring.metrics.export.influx.consistency= # Write consistency for each point.
spring.metrics.export.influx.db= # Tag that will be mapped to "host" when shipping metrics to Influx. Can be omitted if host should be omitted on publishing.
spring.metrics.export.influx.enabled= # Whether exporting of metrics to this backend is enabled.
spring.metrics.export.influx.num-threads= # Number of threads to use with the metrics publishing scheduler.
spring.metrics.export.influx.password= # Login password of the Influx server.
spring.metrics.export.influx.read-timeout= # Read timeout for requests to the backend.
spring.metrics.export.influx.retention-policy= # Retention policy to use (Influx writes to the DEFAULT retention policy if one is not specified).
spring.metrics.export.influx.step=1m # Step size (i.e. reporting frequency) to use.
spring.metrics.export.influx.uri= # URI of the Influx server.
spring.metrics.export.influx.user-name= # Login user of the Influx server.
spring.metrics.export.prometheus.descriptions= # Enable publishing descriptions as part of the scrape payload to Prometheus. Turn this off to minimize the amount of data sent on each scrape.
spring.metrics.export.prometheus.enabled= # Whether exporting of metrics to Prometheus is enabled.
spring.metrics.export.prometheus.step= # Step size (i.e. reporting frequency) to use.
spring.metrics.export.simple.enabled=false # Whether exporting of metrics to a simple in-memory store is enabled.
spring.metrics.export.simple.mode=cumulative # Counting mode.
spring.metrics.export.simple.step=10s # Step size (i.e. reporting frequency) to use.
spring.metrics.export.statsd.enabled= # Export metrics to StatsD.
spring.metrics.export.statsd.flavor=datadog # StatsD line protocol to use.
spring.metrics.export.statsd.host=localhost # Host of the StatsD server to receive exported metrics.
spring.metrics.export.statsd.max-packet-length=1400 # Total length of a single payload should be kept within your network's MTU.
spring.metrics.export.statsd.polling-frequency=10s # How often gauges will be polled. When a gauge is polled, its value is recalculated and if the value has changed, it is sent to the StatsD server.
spring.metrics.export.statsd.port=8125 # Port of the StatsD server to receive exported metrics.
spring.metrics.export.statsd.queue-size=2147483647 # Maximum size of the queue of items waiting to be sent to the StatsD server.
spring.metrics.jdbc.datasource-metric-name=data.source # Name of the metric for data source usage.
spring.metrics.jdbc.instrument-datasource=true # Instrument all available data sources.
spring.metrics.web.client.record-request-percentiles=false # Whether instrumented requests record percentiles histogram buckets by default.
spring.metrics.web.client.requests-metric-name=http.client.requests # Name of the metric for sent requests.
spring.metrics.web.server.auto-time-requests=true # Whether requests handled by Spring MVC or WebFlux should be automatically timed.
spring.metrics.web.server.record-request-percentiles=false # Whether instrumented requests record percentiles histogram buckets by default.
spring.metrics.web.server.requests-metric-name=http.server.requests # Name of the metric for received requests.
# ----------------------------------------
# DEVTOOLS PROPERTIES
# ----------------------------------------
# DEVTOOLS (DevToolsProperties)
spring.devtools.livereload.enabled=true # Whether to enable a livereload.com-compatible server.
spring.devtools.livereload.port=35729 # Server port.
spring.devtools.restart.additional-exclude= # Additional patterns that should be excluded from triggering a full restart.
spring.devtools.restart.additional-paths= # Additional paths to watch for changes.
spring.devtools.restart.enabled=true # Enable automatic restart.
spring.devtools.restart.exclude=META-INF/maven/**,META-INF/resources/**,resources/**,static/**,public/**,templates/**,**/*Test.class,**/*Tests.class,git.properties # Patterns that should be excluded from triggering a full restart.
spring.devtools.restart.log-condition-evaluation-delta=true # Whether to log the condition evaluation delta upon restart.
spring.devtools.restart.poll-interval=1s # Amount of time to wait between polling for classpath changes.
spring.devtools.restart.quiet-period=400ms # Amount of quiet time required without any classpath changes before a restart is triggered.
spring.devtools.restart.trigger-file= # Name of a specific file that, when changed, triggers the restart check. If not specified, any classpath file change triggers the restart.
# REMOTE DEVTOOLS (RemoteDevToolsProperties)
spring.devtools.remote.context-path=/.~~spring-boot!~ # Context path used to handle the remote connection.
spring.devtools.remote.proxy.host= # The host of the proxy to use to connect to the remote application.
spring.devtools.remote.proxy.port= # The port of the proxy to use to connect to the remote application.
spring.devtools.remote.restart.enabled=true # Whether to enable remote restart.
spring.devtools.remote.secret= # A shared secret required to establish a connection (required to enable remote support).
spring.devtools.remote.secret-header-name=X-AUTH-TOKEN # HTTP header used to transfer the shared secret.
# ----------------------------------------
# TESTING PROPERTIES
# ----------------------------------------
spring.test.database.replace=any # Type of existing DataSource to replace.
spring.test.mockmvc.print=default # MVC Print option.

Appendix B. Configuration Metadata

Spring Boot jars include metadata files that provide details of all supported configuration properties. The files are designed to let IDE developers offer contextual help and “code completion” as users are working with application.properties or application.yml files.

The majority of the metadata file is generated automatically at compile time by processing all items annotated with @ConfigurationProperties . However, it is possible to write part of the metadata manually for corner cases or more advanced use cases.

B.1 Metadata Format

Configuration metadata files are located inside jars under META-INF/spring-configuration-metadata.json They use a simple JSON format with items categorized under either “groups” or “properties” and additional values hints categorized under "hints", as shown in the following example:

{"groups": [
		"name": "server",
		"type": "org.springframework.boot.autoconfigure.web.ServerProperties",
		"sourceType": "org.springframework.boot.autoconfigure.web.ServerProperties"
		"name": "spring.jpa.hibernate",
		"type": "org.springframework.boot.autoconfigure.orm.jpa.JpaProperties$Hibernate",
		"sourceType": "org.springframework.boot.autoconfigure.orm.jpa.JpaProperties",
		"sourceMethod": "getHibernate()"
],"properties": [
		"name": "server.port",
		"type": "java.lang.Integer",
		"sourceType": "org.springframework.boot.autoconfigure.web.ServerProperties"
		"name": "server.servlet.path",
		"type": "java.lang.String",
		"sourceType": "org.springframework.boot.autoconfigure.web.ServerProperties",
		"defaultValue": "/"
		  "name": "spring.jpa.hibernate.ddl-auto",
		  "type": "java.lang.String",
		  "description": "DDL mode. This is actually a shortcut for the \"hibernate.hbm2ddl.auto\" property.",
		  "sourceType": "org.springframework.boot.autoconfigure.orm.jpa.JpaProperties$Hibernate"
],"hints": [
		"name": "spring.jpa.hibernate.ddl-auto",
		"values": [
				"value": "none",
				"description": "Disable DDL handling."
				"value": "validate",
				"description": "Validate the schema, make no changes to the database."
				"value": "update",
				"description": "Update the schema if necessary."
				"value": "create",
				"description": "Create the schema and destroy previous data."
				"value": "create-drop",
				"description": "Create and then destroy the schema at the end of the session."
]}

Each “property” is a configuration item that the user specifies with a given value. For example, server.port and server.servlet.path might be specified in application.properties , as follows:

server.port=9090
server.servlet.path=/home

The “groups” are higher level items that do not themselves specify a value but instead provide a contextual grouping for properties. For example, the server.port and server.servlet.path properties are part of the server group.

	Note
	It is not required that every “property” has a “group”. Some properties might exist in their own right.

Finally, “hints” are additional information used to assist the user in configuring a given property. For example, when a developer is configuring the spring.jpa.hibernate.ddl-auto property, a tool can use the hints to offer some auto-completion help for the none , validate , update , create , and create-drop values.

B.1.1 Group Attributes

The JSON object contained in the groups array can contain the attributes shown in the following table:

Name	Type	Purpose
`name`	String	The full name of the group. This attribute is mandatory.
`type`	String	The class name of the data type of the group. For example, if the group were based on a class annotated with `@ConfigurationProperties` , the attribute would contain the fully qualified name of that class. If it were based on a `@Bean` method, it would be the return type of that method. If the type is not known, the attribute may be omitted.
`description`	String	A short description of the group that can be displayed to users. If not description is available, it may be omitted. It is recommended that descriptions be short paragraphs, with the first line providing a concise summary. The last line in the description should end with a period ( `.` ).
`sourceType`	String	The class name of the source that contributed this group. For example, if the group were based on a `@Bean` method annotated with `@ConfigurationProperties` , this attribute would contain the fully qualified name of the `@Configuration` class that contains the method. If the source type is not known, the attribute may be omitted.
`sourceMethod`	String	The full name of the method (include parenthesis and argument types) that contributed this group (for example, the name of a `@ConfigurationProperties` annotated `@Bean` method). If the source method is not known, it may be omitted.

B.1.2 Property Attributes

The JSON object contained in the properties array can contain the attributes described in the following table:

Name	Type	Purpose
`name`	String	The full name of the property. Names are in lower-case period-separated form (for example, `server.servlet.path` ). This attribute is mandatory.
`type`	String	The full signature of the data type of the property (for example, `java.lang.String` ) but also a full generic type (such as `java.util.Map<java.util.String,acme.MyEnum>` ). You can use this attribute to guide the user as to the types of values that they can enter. For consistency, the type of a primitive is specified by using its wrapper counterpart (for example, `boolean` becomes `java.lang.Boolean` ). Note that this class may be a complex type that gets converted from a `String` as values are bound. If the type is not known, it may be omitted.
`description`	String	A short description of the group that can be displayed to users. If no description is available, it may be omitted. It is recommended that descriptions be short paragraphs, with the first line providing a concise summary. The last line in the description should end with a period ( `.` ).
`sourceType`	String	The class name of the source that contributed this property. For example, if the property were from a class annotated with `@ConfigurationProperties` , this attribute would contain the fully qualified name of that class. If the source type is unknown, it may be omitted.
`defaultValue`	Object	The default value, which is used if the property is not specified. If the type of the property is an array, it can be an array of value(s). If the default value is unknown, it may be omitted.
`deprecation`	Deprecation	Specify whether the property is deprecated. If the field is not deprecated or if that information is not known, it may be omitted. The next table offers more detail about the `deprecation` attribute.

The JSON object contained in the deprecation attribute of each properties element can contain the following attributes:

Name	Type	Purpose
`level`	String	The level of deprecation, which can be either `warning` (the default) or `error` . When a property has a `warning` deprecation level, it should still be bound in the environment. However, when it has an `error` deprecation level, the property is no longer managed and is not bound.
`reason`	String	A short description of the reason why the property was deprecated. If no reason is available, it may be omitted. It is recommended that descriptions be short paragraphs, with the first line providing a concise summary. The last line in the description should end with a period ( `.` ).
`replacement`	String	The full name of the property that replaces this deprecated property. If there is no replacement for this property, it may be omitted.

	Note
	Prior to Spring Boot 1.3, a single `deprecated` boolean attribute can be used instead of the `deprecation` element. This is still supported in a deprecated fashion and should no longer be used. If no reason and replacement are available, an empty `deprecation` object should be set.

Deprecation can also be specified declaratively in code by adding the @DeprecatedConfigurationProperty annotation to the getter exposing the deprecated property. For instance, assume that the app.foo.target property was confusing and was renamed to app.foo.name . The following example shows how to handle that situation:

@ConfigurationProperties("app.foo")
public class FooProperties {
	private String name;
	public String getName() { ... }
	public void setName(String name) { ... }
	@DeprecatedConfigurationProperty(replacement = "app.foo.name")
	@Deprecated
	public String getTarget() {
		return getName();
	@Deprecated
	public void setTarget(String target) {
		setName(target);
}

	Note
	There is no way to set a `level` . `warning` is always assumed, since code is still handling the property.

The preceding code makes sure that the deprecated property still works (delegating to the name property behind the scenes). Once the getTarget and setTarget methods can be removed from your public API, the automatic deprecation hint in the metadata goes away as well. If you want to keep a hint, adding manual metadata with an error deprecation level ensures that users are still informed about that property. Doing so is particularly useful when a replacement is provided.

B.1.3 Hint Attributes

The JSON object contained in the hints array can contain the attributes shown in the following table:

Name	Type	Purpose
`name`	String	The full name of the property to which this hint refers. Names are in lower-case period-separated form (such as `server.servlet.path` ). If the property refers to a map (such as `system.contexts` ), the hint either applies to the keys of the map ( `system.context.keys` ) or the values ( `system.context.values` ) of the map. This attribute is mandatory.
`values`	ValueHint[]	A list of valid values as defined by the `ValueHint` object (described in the next table). Each entry defines the value and may have a description.
`providers`	ValueProvider[]	A list of providers as defined by the `ValueProvider` object (described later in this document). Each entry defines the name of the provider and its parameters, if any.

The JSON object contained in the values attribute of each hint element can contain the attributes described in the following table:

Name	Type	Purpose
`value`	Object	A valid value for the element to which the hint refers. If the type of the property is an array, it can also be an array of value(s). This attribute is mandatory.
`description`	String	A short description of the value that can be displayed to users. If no description is available, it may be omitted . It is recommended that descriptions be short paragraphs, with the first line providing a concise summary. The last line in the description should end with a period ( `.` ).

The JSON object contained in the providers attribute of each hint element can contain the attributes described in the following table:

Name	Type	Purpose
`name`	String	The name of the provider to use to offer additional content assistance for the element to which the hint refers.
`parameters`	JSON object	Any additional parameter that the provider supports (check the documentation of the provider for more details).

B.1.4 Repeated Metadata Items

Objects with the same “property” and “group” name can appear multiple times within a metadata file. For example, you could bind two separate classes to the same prefix, with each having potentially overlapping property names. While the same names appearing in the metadata multiple times should not be common, consumers of metadata should take care to ensure that they support it.

B.2 Providing Manual Hints

To improve the user experience and further assist the user in configuring a given property, you can provide additional metadata that:

Describes the list of potential values for a property.
Associates a provider, to attach a well defined semantic to a property, so that a tool can discover the list of potential values based on the project’s context.

B.2.1 Value Hint

The name attribute of each hint refers to the name of a property. In the initial example shown earlier , we provide five values for the spring.jpa.hibernate.ddl-auto property: none , validate , update , create , and create-drop . Each value may have a description as well.

If your property is of type Map , you can provide hints for both the keys and the values (but not for the map itself). The special .keys and .values suffixes must refer to the keys and the values, respectively.

Assume a sample.contexts maps magic String values to an integer, as shown in the following example:

@ConfigurationProperties("sample")
public class SampleProperties {
	private Map<String,Integer> contexts;
	// getters and setters
}

The magic values are (in this example) are sample1 and sample2 . In order to offer additional content assistance for the keys, you could add the following JSON to the manual metadata of the module :

{"hints": [
		"name": "sample.contexts.keys",
		"values": [
				"value": "sample1"
				"value": "sample2"
]}

	Tip
	We recommend that you use an `Enum` for those two values instead. If your IDE supports it, this is by far the most effective approach to auto-completion.

B.2.2 Value Providers

Providers are a powerful way to attach semantics to a property. In this section, we define the official providers that you can use for your own hints. However, your favorite IDE may implement some of these or none of them. Also, it could eventually provide its own.

	Note
	As this is a new feature, IDE vendors must catch up with how it works. Adoption times naturally vary.

The following table summarizes the list of supported providers:

Name	Description
`any`	Permits any additional value to be provided.
`class-reference`	Auto-completes the classes available in the project. Usually constrained by a base class that is specified by the `target` parameter.
`handle-as`	Handles the property as if it were defined by the type defined by the mandatory `target` parameter.
`logger-name`	Auto-completes valid logger names. Typically, package and class names available in the current project can be auto-completed.
`spring-bean-reference`	Auto-completes the available bean names in the current project. Usually constrained by a base class that is specified by the `target` parameter.
`spring-profile-name`	Auto-completes the available Spring profile names in the project.

	Tip
	Only one provider can be active for a given property, but you can specify several providers if they can all manage the property in some way . Make sure to place the most powerful provider first, as the IDE must use the first one in the JSON section that it can handle. If no provider for a given property is supported, no special content assistance is provided, either.

Any

The special any provider value permits any additional values to be provided. Regular value validation based on the property type should be applied if this is supported.

This provider is typically used if you have a list of values and any extra values should still be considered as valid.

The following example offers on and off as auto-completion values for system.state :

{"hints": [
		"name": "system.state",
		"values": [
				"value": "on"
				"value": "off"
		"providers": [
				"name": "any"
]}

Note that, in the preceding example, any other value is also allowed.

Class Reference

The class-reference provider auto-completes classes available in the project. This provider supports the following parameters:

Parameter	Type	Default value	Description
`target`	`String` ( `Class` )	none	The fully qualified name of the class that should be assignable to the chosen value. Typically used to filter out-non candidate classes. Note that this information can be provided by the type itself by exposing a class with the appropriate upper bound.
`concrete`	`boolean`	true	Specify whether only concrete classes are to be considered as valid candidates.

The following metadata snippet corresponds to the standard server.servlet.jsp.class-name property that defines the JspServlet class name to use:

{"hints": [
		"name": "server.servlet.jsp.class-name",
		"providers": [
				"name": "class-reference",
				"parameters": {
					"target": "javax.servlet.http.HttpServlet"
]}

Handle As

The handle-as provider lets you substitute the type of the property to a more high-level type. This typically happens when the property has a java.lang.String type, because you do not want your configuration classes to rely on classes that may not be on the classpath. This provider supports the following parameters:

Parameter	Type	Default value	Description
`target`	`String` ( `Class` )	none	The fully qualified name of the type to consider for the property. This parameter is mandatory.

The following types can be used:

Any java.lang.Enum : Lists the possible values for the property. (We recommend defining the property with the Enum type, as no further hint should be required for the IDE to auto-complete the values.)
java.nio.charset.Charset : Supports auto-completion of charset/encoding values (such as UTF-8 )
java.util.Locale : auto-completion of locales (such as en_US )
org.springframework.util.MimeType : Supports auto-completion of content type values (such as text/plain )
org.springframework.core.io.Resource : Supports auto-completion of Spring’s Resource abstraction to refer to a file on the filesystem or on the classpath. (such as classpath:/sample.properties )

	Tip
	If multiple values can be provided, use a `Collection` or Array type to teach the IDE about it.

The following metadata snippet corresponds to the standard spring.liquibase.change-log property that defines the path to the changelog to use. It is actually used internally as a org.springframework.core.io.Resource but cannot be exposed as such, because we need to keep the original String value to pass it to the Liquibase API.

{"hints": [
		"name": "spring.liquibase.change-log",
		"providers": [
				"name": "handle-as",
				"parameters": {
					"target": "org.springframework.core.io.Resource"
]}

Logger Name

The logger-name provider auto-completes valid logger names. Typically, package and class names available in the current project can be auto-completed. Specific frameworks may have extra magic logger names that can be supported as well.

Since a logger name can be any arbitrary name, this provider should allow any value but could highlight valid package and class names that are not available in the project’s classpath.

The following metadata snippet corresponds to the standard logging.level property. Keys are logger names , and values correspond to the standard log levels or any custom level.

{"hints": [
		"name": "logging.level.keys",
		"values": [
				"value": "root",
				"description": "Root logger used to assign the default logging level."
		"providers": [
				"name": "logger-name"
		"name": "logging.level.values",
		"values": [
				"value": "trace"
				"value": "debug"
				"value": "info"
				"value": "warn"
				"value": "error"
				"value": "fatal"
				"value": "off"
		"providers": [
				"name": "any"
]}

Spring Bean Reference

The spring-bean-reference provider auto-completes the beans that are defined in the configuration of the current project. This provider supports the following parameters:

Parameter	Type	Default value	Description
`target`	`String` ( `Class` )	none	The fully qualified name of the bean class that should be assignable to the candidate. Typically used to filter out non-candidate beans.

The following metadata snippet corresponds to the standard spring.jmx.server property that defines the name of the MBeanServer bean to use:

{"hints": [
		"name": "spring.jmx.server",
		"providers": [
				"name": "spring-bean-reference",
				"parameters": {
					"target": "javax.management.MBeanServer"
]}

	Note
	The binder is not aware of the metadata. If you provide that hint, you still need to transform the bean name into an actual Bean reference using by the `ApplicationContext` .

Spring Profile Name

The spring-profile-name provider auto-completes the Spring profiles that are defined in the configuration of the current project.

The following metadata snippet corresponds to the standard spring.profiles.active property that defines the name of the Spring profile(s) to enable:

{"hints": [
		"name": "spring.profiles.active",
		"providers": [
				"name": "spring-profile-name"
]}

B.3 Generating Your Own Metadata by Using the Annotation Processor

You can easily generate your own configuration metadata file from items annotated with @ConfigurationProperties by using the spring-boot-configuration-processor jar. The jar includes a Java annotation processor which is invoked as your project is compiled. To use the processor, include spring-boot-configuration-processor as an optional dependency. For example, with Maven, you can add:

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-configuration-processor</artifactId>
	<optional>true</optional>
</dependency>

With Gradle, you can use the propdeps-plugin and specify the following dependency:

dependencies {
	optional "org.springframework.boot:spring-boot-configuration-processor"
compileJava.dependsOn(processResources)

	Note
	You need to add `compileJava.dependsOn(processResources)` to your build to ensure that resources are processed before code is compiled. Without this directive, any `additional-spring-configuration-metadata.json` files are not processed.

The processor picks up both classes and methods that are annotated with @ConfigurationProperties . The Javadoc for field values within configuration classes is used to populate the description attribute.

	Note
	You should only use simple text with `@ConfigurationProperties` field Javadoc, since they are not processed before being added to the JSON.

Properties are discovered through the presence of standard getters and setters with special handling for collection types (that is detected even if only a getter is present). The annotation processor also supports the use of the @Data , @Getter , and @Setter lombok annotations.

Note

If you are using AspectJ in your project, you need to make sure that the annotation processor runs only once. There are several ways to do this. With Maven, you can configure the maven-apt-plugin explicitly and add the dependency to the annotation processor only there. You could also let the AspectJ plugin run all the processing and disable annotation processing in the maven-compiler-plugin configuration, as follows:

<plugin>
	<groupId>org.apache.maven.plugins</groupId>
	<artifactId>maven-compiler-plugin</artifactId>
	<configuration>
		<proc>none</proc>
	</configuration>
</plugin>

B.3.1 Nested Properties

The annotation processor automatically considers inner classes as nested properties. Consider the following class:

@ConfigurationProperties(prefix="server")
public class ServerProperties {
	private String name;
	private Host host;
	// ... getter and setters
	private static class Host {
		private String ip;
		private int port;
		// ... getter and setters
}

The preceding example produces metadata information for server.name , server.host.ip , and server.host.port properties. You can use the @NestedConfigurationProperty annotation on a field to indicate that a regular (non-inner) class should be treated as if it were nested.

	Tip
	This has no effect on collections and maps, as those types are automatically identified, and a single metadata property is generated for each of them.

B.3.2 Adding Additional Metadata

Spring Boot’s configuration file handling is quite flexible, and it is often the case that properties may exist that are not bound to a @ConfigurationProperties bean. You may also need to tune some attributes of an existing key. To support such cases and let you provide custom "hints", the annotation processor automatically merges items from META-INF/additional-spring-configuration-metadata.json into the main metadata file.

If you refer to a property that has been detected automatically, the description, default value, and deprecation information are overridden, if specified. If the manual property declaration is not identified in the current module, it is added as a new property.

The format of the additional-spring-configuration-metadata.json file is exactly the same as the regular spring-configuration-metadata.json . The additional properties file is optional. If you do not have any additional properties, do not add the file.

Appendix C. Auto-configuration classes

Here is a list of all auto-configuration classes provided by Spring Boot, with links to documentation and source code. Remember to also look at the conditions report in your application for more details of which features are switched on. (To do so, start the app with --debug or -Ddebug or, in an Actuator application, use the conditions endpoint).

C.1 From the “spring-boot-autoconfigure” module

The following auto-configuration classes are from the spring-boot-autoconfigure module:

Configuration Class	Links
`ActiveMQAutoConfiguration`	javadoc
`AopAutoConfiguration`	javadoc
`ArtemisAutoConfiguration`	javadoc
`BatchAutoConfiguration`	javadoc
`CacheAutoConfiguration`	javadoc
`CassandraAutoConfiguration`	javadoc
`CassandraDataAutoConfiguration`	javadoc
`CassandraReactiveDataAutoConfiguration`	javadoc
`CassandraReactiveRepositoriesAutoConfiguration`	javadoc
`CassandraRepositoriesAutoConfiguration`	javadoc
`CloudAutoConfiguration`	javadoc
`CodecsAutoConfiguration`	javadoc
`ConfigurationPropertiesAutoConfiguration`	javadoc
`CouchbaseAutoConfiguration`	javadoc
`CouchbaseDataAutoConfiguration`	javadoc
`CouchbaseReactiveDataAutoConfiguration`	javadoc
`CouchbaseReactiveRepositoriesAutoConfiguration`	javadoc
`CouchbaseRepositoriesAutoConfiguration`	javadoc
`DataSourceAutoConfiguration`	javadoc
`DataSourceTransactionManagerAutoConfiguration`	javadoc
`DispatcherServletAutoConfiguration`	javadoc
`ElasticsearchAutoConfiguration`	javadoc
`ElasticsearchDataAutoConfiguration`	javadoc
`ElasticsearchRepositoriesAutoConfiguration`	javadoc
`EmbeddedLdapAutoConfiguration`	javadoc
`EmbeddedMongoAutoConfiguration`	javadoc
`ErrorMvcAutoConfiguration`	javadoc
`ErrorWebFluxAutoConfiguration`	javadoc
`FlywayAutoConfiguration`	javadoc
`FreeMarkerAutoConfiguration`	javadoc
`GroovyTemplateAutoConfiguration`	javadoc
`GsonAutoConfiguration`	javadoc
`H2ConsoleAutoConfiguration`	javadoc
`HazelcastAutoConfiguration`	javadoc
`HazelcastJpaDependencyAutoConfiguration`	javadoc
`HibernateJpaAutoConfiguration`	javadoc
`HttpEncodingAutoConfiguration`	javadoc
`HttpHandlerAutoConfiguration`	javadoc
`HttpMessageConvertersAutoConfiguration`	javadoc
`HypermediaAutoConfiguration`	javadoc
`InfluxDbAutoConfiguration`	javadoc
`IntegrationAutoConfiguration`	javadoc
`JacksonAutoConfiguration`	javadoc
`JdbcTemplateAutoConfiguration`	javadoc
`JerseyAutoConfiguration`	javadoc
`JestAutoConfiguration`	javadoc
`JmsAutoConfiguration`	javadoc
`JmxAutoConfiguration`	javadoc
`JndiConnectionFactoryAutoConfiguration`	javadoc
`JndiDataSourceAutoConfiguration`	javadoc
`JooqAutoConfiguration`	javadoc
`JpaRepositoriesAutoConfiguration`	javadoc
`JsonbAutoConfiguration`	javadoc
`JtaAutoConfiguration`	javadoc
`KafkaAutoConfiguration`	javadoc
`LdapAutoConfiguration`	javadoc
`LdapDataAutoConfiguration`	javadoc
`LdapRepositoriesAutoConfiguration`	javadoc
`LiquibaseAutoConfiguration`	javadoc
`MailSenderAutoConfiguration`	javadoc
`MailSenderValidatorAutoConfiguration`	javadoc
`MessageSourceAutoConfiguration`	javadoc
`MongoAutoConfiguration`	javadoc
`MongoDataAutoConfiguration`	javadoc
`MongoReactiveAutoConfiguration`	javadoc
`MongoReactiveDataAutoConfiguration`	javadoc
`MongoReactiveRepositoriesAutoConfiguration`	javadoc
`MongoRepositoriesAutoConfiguration`	javadoc
`MultipartAutoConfiguration`	javadoc
`MustacheAutoConfiguration`	javadoc
`Neo4jDataAutoConfiguration`	javadoc
`Neo4jRepositoriesAutoConfiguration`	javadoc
`OAuth2ClientAutoConfiguration`	javadoc
`PersistenceExceptionTranslationAutoConfiguration`	javadoc
`ProjectInfoAutoConfiguration`	javadoc
`PropertyPlaceholderAutoConfiguration`	javadoc
`QuartzAutoConfiguration`	javadoc
`RabbitAutoConfiguration`	javadoc
`ReactiveSecurityAutoConfiguration`	javadoc
`ReactiveWebServerAutoConfiguration`	javadoc
`ReactorCoreAutoConfiguration`	javadoc
`RedisAutoConfiguration`	javadoc
`RedisReactiveAutoConfiguration`	javadoc
`RedisRepositoriesAutoConfiguration`	javadoc
`RepositoryRestMvcAutoConfiguration`	javadoc
`RestTemplateAutoConfiguration`	javadoc
`SecurityAutoConfiguration`	javadoc
`SecurityFilterAutoConfiguration`	javadoc
`SendGridAutoConfiguration`	javadoc
`ServletWebServerFactoryAutoConfiguration`	javadoc
`SessionAutoConfiguration`	javadoc
`SolrAutoConfiguration`	javadoc
`SolrRepositoriesAutoConfiguration`	javadoc
`SpringApplicationAdminJmxAutoConfiguration`	javadoc
`SpringDataWebAutoConfiguration`	javadoc
`ThymeleafAutoConfiguration`	javadoc
`TransactionAutoConfiguration`	javadoc
`ValidationAutoConfiguration`	javadoc
`WebClientAutoConfiguration`	javadoc
`WebFluxAutoConfiguration`	javadoc
`WebMvcAutoConfiguration`	javadoc
`WebServicesAutoConfiguration`	javadoc
`WebSocketMessagingAutoConfiguration`	javadoc
`WebSocketReactiveAutoConfiguration`	javadoc
`WebSocketServletAutoConfiguration`	javadoc
`XADataSourceAutoConfiguration`	javadoc

C.2 From the “spring-boot-actuator-autoconfigure” module

The following auto-configuration classes are from the spring-boot-actuator-autoconfigure module:

Configuration Class	Links
`AuditAutoConfiguration`	javadoc
`AuditEventsEndpointAutoConfiguration`	javadoc
`BeansEndpointAutoConfiguration`	javadoc
`CassandraHealthIndicatorAutoConfiguration`	javadoc
`CloudFoundryActuatorAutoConfiguration`	javadoc
`CloudFoundryHealthWebEndpointManagementContextConfiguration`	javadoc
`ConditionsReportEndpointAutoConfiguration`	javadoc
`ConfigurationPropertiesReportEndpointAutoConfiguration`	javadoc
`CouchbaseHealthIndicatorAutoConfiguration`	javadoc
`DataSourceHealthIndicatorAutoConfiguration`	javadoc
`DiskSpaceHealthIndicatorAutoConfiguration`	javadoc
`ElasticsearchHealthIndicatorAutoConfiguration`	javadoc
`EndpointAutoConfiguration`	javadoc
`EnvironmentEndpointAutoConfiguration`	javadoc
`FlywayEndpointAutoConfiguration`	javadoc
`HealthEndpointAutoConfiguration`	javadoc
`HealthIndicatorAutoConfiguration`	javadoc
`HeapDumpWebEndpointAutoConfiguration`	javadoc
`InfoContributorAutoConfiguration`	javadoc
`InfoEndpointAutoConfiguration`	javadoc
`JmsHealthIndicatorAutoConfiguration`	javadoc
`JmxEndpointAutoConfiguration`	javadoc
`LdapHealthIndicatorAutoConfiguration`	javadoc
`LiquibaseEndpointAutoConfiguration`	javadoc
`LogFileWebEndpointAutoConfiguration`	javadoc
`LoggersEndpointAutoConfiguration`	javadoc
`MailHealthIndicatorAutoConfiguration`	javadoc
`ManagementContextAutoConfiguration`	javadoc
`MetricsAutoConfiguration`	javadoc
`MongoHealthIndicatorAutoConfiguration`	javadoc
`Neo4jHealthIndicatorAutoConfiguration`	javadoc
`RabbitHealthIndicatorAutoConfiguration`	javadoc
`ReactiveCloudFoundryActuatorAutoConfiguration`	javadoc
`ReactiveManagementContextAutoConfiguration`	javadoc
`RedisHealthIndicatorAutoConfiguration`	javadoc
`RequestMappingEndpointAutoConfiguration`	javadoc
`ScheduledTasksEndpointAutoConfiguration`	javadoc
`ServletManagementContextAutoConfiguration`	javadoc
`SessionsEndpointAutoConfiguration`	javadoc
`ShutdownEndpointAutoConfiguration`	javadoc
`SolrHealthIndicatorAutoConfiguration`	javadoc
`ThreadDumpEndpointAutoConfiguration`	javadoc
`TraceEndpointAutoConfiguration`	javadoc
`TraceRepositoryAutoConfiguration`	javadoc
`TraceWebFilterAutoConfiguration`	javadoc
`WebEndpointAutoConfiguration`	javadoc

Appendix D. Test auto-configuration annotations

The following table lists the various @…Test annotations that can be used to test slices of your application and the auto-configuration that they import by default:

Test slice	Imported auto-configuration
`@DataJpaTest`	`org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration` `org.springframework.boot.autoconfigure.data.jpa.JpaRepositoriesAutoConfiguration` `org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration` `org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration` `org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration` `org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration` `org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration` `org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration` `org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration` `org.springframework.boot.test.autoconfigure.jdbc.TestDatabaseAutoConfiguration` `org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManagerAutoConfiguration`
`@DataLdapTest`	`org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration` `org.springframework.boot.autoconfigure.data.ldap.LdapDataAutoConfiguration` `org.springframework.boot.autoconfigure.data.ldap.LdapRepositoriesAutoConfiguration` `org.springframework.boot.autoconfigure.ldap.LdapAutoConfiguration` `org.springframework.boot.autoconfigure.ldap.embedded.EmbeddedLdapAutoConfiguration`
`@DataMongoTest`	`org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration` `org.springframework.boot.autoconfigure.data.mongo.MongoDataAutoConfiguration` `org.springframework.boot.autoconfigure.data.mongo.MongoReactiveDataAutoConfiguration` `org.springframework.boot.autoconfigure.data.mongo.MongoReactiveRepositoriesAutoConfiguration` `org.springframework.boot.autoconfigure.data.mongo.MongoRepositoriesAutoConfiguration` `org.springframework.boot.autoconfigure.mongo.MongoAutoConfiguration` `org.springframework.boot.autoconfigure.mongo.MongoReactiveAutoConfiguration` `org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongoAutoConfiguration`
`@DataNeo4jTest`	`org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration` `org.springframework.boot.autoconfigure.data.neo4j.Neo4jDataAutoConfiguration` `org.springframework.boot.autoconfigure.data.neo4j.Neo4jRepositoriesAutoConfiguration` `org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration`
`@DataRedisTest`	`org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration` `org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration` `org.springframework.boot.autoconfigure.data.redis.RedisRepositoriesAutoConfiguration`
`@JdbcTest`	`org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration` `org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration` `org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration` `org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration` `org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration` `org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration` `org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration` `org.springframework.boot.test.autoconfigure.jdbc.TestDatabaseAutoConfiguration`
`@JooqTest`	`org.springframework.boot.autoconfigure.flyway.FlywayAutoConfiguration` `org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration` `org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration` `org.springframework.boot.autoconfigure.jooq.JooqAutoConfiguration` `org.springframework.boot.autoconfigure.liquibase.LiquibaseAutoConfiguration` `org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration`
`@JsonTest`	`org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration` `org.springframework.boot.autoconfigure.gson.GsonAutoConfiguration` `org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration` `org.springframework.boot.autoconfigure.jsonb.JsonbAutoConfiguration` `org.springframework.boot.test.autoconfigure.json.JsonTestersAutoConfiguration`
`@RestClientTest`	`org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration` `org.springframework.boot.autoconfigure.gson.GsonAutoConfiguration` `org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration` `org.springframework.boot.autoconfigure.http.codec.CodecsAutoConfiguration` `org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration` `org.springframework.boot.autoconfigure.jsonb.JsonbAutoConfiguration` `org.springframework.boot.autoconfigure.web.client.RestTemplateAutoConfiguration` `org.springframework.boot.autoconfigure.web.reactive.function.client.WebClientAutoConfiguration` `org.springframework.boot.test.autoconfigure.web.client.MockRestServiceServerAutoConfiguration` `org.springframework.boot.test.autoconfigure.web.client.WebClientRestTemplateAutoConfiguration`
`@WebFluxTest`	`org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration` `org.springframework.boot.autoconfigure.context.MessageSourceAutoConfiguration` `org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration` `org.springframework.boot.autoconfigure.web.reactive.WebFluxAutoConfiguration` `org.springframework.boot.test.autoconfigure.web.reactive.WebTestClientAutoConfiguration`
`@WebMvcTest`	`org.springframework.boot.autoconfigure.cache.CacheAutoConfiguration` `org.springframework.boot.autoconfigure.context.MessageSourceAutoConfiguration` `org.springframework.boot.autoconfigure.freemarker.FreeMarkerAutoConfiguration` `org.springframework.boot.autoconfigure.groovy.template.GroovyTemplateAutoConfiguration` `org.springframework.boot.autoconfigure.gson.GsonAutoConfiguration` `org.springframework.boot.autoconfigure.hateoas.HypermediaAutoConfiguration` `org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration` `org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration` `org.springframework.boot.autoconfigure.jsonb.JsonbAutoConfiguration` `org.springframework.boot.autoconfigure.mustache.MustacheAutoConfiguration` `org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration` `org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration` `org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration` `org.springframework.boot.autoconfigure.web.servlet.error.ErrorMvcAutoConfiguration` `org.springframework.boot.test.autoconfigure.web.servlet.MockMvcAutoConfiguration` `org.springframework.boot.test.autoconfigure.web.servlet.MockMvcSecurityAutoConfiguration` `org.springframework.boot.test.autoconfigure.web.servlet.MockMvcWebClientAutoConfiguration` `org.springframework.boot.test.autoconfigure.web.servlet.MockMvcWebDriverAutoConfiguration`

Appendix E. The Executable Jar Format

The spring-boot-loader modules lets Spring Boot support executable jar and war files. If you use the Maven plugin or the Gradle plugin, executable jars are automatically generated, and you generally do not need to know the details of how they work.

If you need to create executable jars from a different build system or if you are just curious about the underlying technology, this section provides some background.

E.1 Nested JARs

Java does not provide any standard way to load nested jar files (that is, jar files that are themselves contained within a jar). This can be problematic if you need to distribute a self-contained application that can be run from the command line without unpacking.

To solve this problem, many developers use “shaded” jars. A shaded jar packages all classes, from all jars, into a single “uber jar”. The problem with shaded jars is that it becomes hard to see which libraries are actually in your application. It can also be problematic if the same filename is used (but with different content) in multiple jars. Spring Boot takes a different approach and lets you actually nest jars directly.

E.1.1 The Executable Jar File Structure

Spring Boot Loader-compatible jar files should be structured in the following way:

example.jar
 +-META-INF
 |  +-MANIFEST.MF
 +-org
 |  +-springframework
 |     +-boot
 |        +-loader
 |           +-<spring boot loader classes>
 +-BOOT-INF
    +-classes
    |  +-mycompany
    |     +-project
    |        +-YourClasses.class
    +-lib
       +-dependency1.jar
       +-dependency2.jar

Application classes should be placed in a nested BOOT-INF/classes directory. Dependencies should be placed in a nested BOOT-INF/lib directory.

E.1.2 The Executable War File Structure

Spring Boot Loader-compatible war files should be structured in the following way:

example.war
 +-META-INF
 |  +-MANIFEST.MF
 +-org
 |  +-springframework
 |     +-boot
 |        +-loader
 |           +-<spring boot loader classes>
 +-WEB-INF
    +-classes
    |  +-com
    |     +-mycompany
    |        +-project
    |           +-YourClasses.class
    +-lib
    |  +-dependency1.jar
    |  +-dependency2.jar
    +-lib-provided
       +-servlet-api.jar
       +-dependency3.jar

Dependencies should be placed in a nested WEB-INF/lib directory. Any dependencies that are required when running embedded but are not required when deploying to a traditional web container should be placed in WEB-INF/lib-provided .

E.2 Spring Boot’s “JarFile” Class

The core class used to support loading nested jars is org.springframework.boot.loader.jar.JarFile . It lets you load jar content from a standard jar file or from nested child jar data. When first loaded, the location of each JarEntry is mapped to a physical file offset of the outer jar, as shown in the following example:

myapp.jar
+-------------------+-------------------------+
| /BOOT-INF/classes | /BOOT-INF/lib/mylib.jar |
|+-----------------+||+-----------+----------+|
||     A.class      |||  B.class  |  C.class ||
|+-----------------+||+-----------+----------+|
+-------------------+-------------------------+
 ^                    ^           ^
 0063                 3452        3980

The preceding example shows how A.class can be found in /BOOT-INF/classes in myapp.jar at position 0063 . B.class from the nested jar can actually be found in myapp.jar at position 3452 , and C.class is at position 3980 .

Armed with this information, we can load specific nested entries by seeking to the appropriate part of the outer jar. We do not need to unpack the archive, and we do not need to read all entry data into memory.

E.2.1 Compatibility with the Standard Java “JarFile”

Spring Boot Loader strives to remain compatible with existing code and libraries. org.springframework.boot.loader.jar.JarFile extends from java.util.jar.JarFile and should work as a drop-in replacement. The getURL() method returns a URL that opens a connection compatible with java.net.JarURLConnection and can be used with Java’s URLClassLoader .

E.3 Launching Executable Jars

The org.springframework.boot.loader.Launcher class is a special bootstrap class that is used as an executable jar’s main entry point. It is the actual Main-Class in your jar file, and it is used to setup an appropriate URLClassLoader and ultimately call your main() method.

There are three launcher subclasses ( JarLauncher , WarLauncher , and PropertiesLauncher ). Their purpose is to load resources ( .class files and so on.) from nested jar files or war files in directories (as opposed to those explicitly on the classpath). In the case of JarLauncher and WarLauncher , the nested paths are fixed. JarLauncher looks in BOOT-INF/lib/ , and WarLauncher looks in WEB-INF/lib/ and WEB-INF/lib-provided/ . You can add extra jars in those locations if you want more. The PropertiesLauncher looks in BOOT-INF/lib/ in your application archive by default, but you can add additional locations by setting an environment variable called LOADER_PATH or loader.path in loader.properties (which is a comma-separated list of directories, archives, or directories within archives).

E.3.1 Launcher Manifest

You need to specify an appropriate Launcher as the Main-Class attribute of META-INF/MANIFEST.MF . The actual class that you want to launch (that is, the class that contains a main method) should be specified in the Start-Class attribute.

The following example shows a typical MANIFEST.MF for an executable jar file:

Main-Class: org.springframework.boot.loader.JarLauncher
Start-Class: com.mycompany.project.MyApplication

For a war file, it would be as follows:

Main-Class: org.springframework.boot.loader.WarLauncher
Start-Class: com.mycompany.project.MyApplication

	Note
	You need not specify `Class-Path` entries in your manifest file. The classpath is deduced from the nested jars.

E.3.2 Exploded Archives

Certain PaaS implementations may choose to unpack archives before they run. For example, Cloud Foundry operates this way. You can run an unpacked archive by starting the appropriate launcher, as follows:

$ unzip -q myapp.jar
$ java org.springframework.boot.loader.JarLauncher

E.4 `PropertiesLauncher` Features

PropertiesLauncher has a few special features that can be enabled with external properties (System properties, environment variables, manifest entries, or loader.properties ). The following table describes these properties:

Key	Purpose
`loader.path`	Comma-separated Classpath, such as `lib,${HOME}/app/lib` . Earlier entries take precedence, like a regular `-classpath` on the `javac` command line.
`loader.home`	Used to resolve relative paths in `loader.path` . For example, given `loader.path=lib` , then `${loader.home}/lib` is a classpath location (along with all jar files in that directory). This property is also used to locate a `loader.properties` file, as in the following example `/opt/app` It defaults to `${user.dir}` .
`loader.args`	Default arguments for the main method (space separated).
`loader.main`	Name of main class to launch (for example, `com.app.Application` ).
`loader.config.name`	Name of properties file (for example, `launcher` ) It defaults to `loader` .
`loader.config.location`	Path to properties file (for example, `classpath:loader.properties` ). It defaults to `loader.properties` .
`loader.system`	Boolean flag to indicate that all properties should be added to System properties It defaults to `false` .

When specified as environment variables or manifest entries, the following names should be used:

Key	Manifest entry	Environment variable
`loader.path`	`Loader-Path`	`LOADER_PATH`
`loader.home`	`Loader-Home`	`LOADER_HOME`
`loader.args`	`Loader-Args`	`LOADER_ARGS`
`loader.main`	`Start-Class`	`LOADER_MAIN`
`loader.config.location`	`Loader-Config-Location`	`LOADER_CONFIG_LOCATION`
`loader.system`	`Loader-System`	`LOADER_SYSTEM`

	Tip
	Build plugins automatically move the `Main-Class` attribute to `Start-Class` when the fat jar is built. If you use that, specify the name of the class to launch by using the `Main-Class` attribute and leaving out `Start-Class` .

The following rules apply to working with PropertiesLauncher :

loader.properties is searched for in loader.home , then in the root of the classpath, and then in classpath:/BOOT-INF/classes . The first location where a file with that name exists is used.
loader.home is the directory location of an additional properties file (overriding the default) only when loader.config.location is not specified.
loader.path can contain directories (which are scanned recursively for jar and zip files), archive paths, a directory within an archive that is scanned for jar files (for example, dependencies.jar!/lib ), or wildcard patterns (for the default JVM behavior). Archive paths can be relative to loader.home or anywhere in the file system with a jar:file: prefix.
loader.path (if empty) defaults to BOOT-INF/lib (meaning a local directory or a nested one if running from an archive). Because of this, PropertiesLauncher behaves the same as JarLauncher when no additional configuration is provided.
loader.path can not be used to configure the location of loader.properties (the classpath used to search for the latter is the JVM classpath when PropertiesLauncher is launched).
Placeholder replacement is done from System and environment variables plus the properties file itself on all values before use.
The search order for properties (where it makes sense to look in more than one place) is environment variables, system properties, loader.properties , the exploded archive manifest, and the archive manifest.

E.5 Executable Jar Restrictions

You need to consider the following restrictions when working with a Spring Boot Loader packaged application:

Zip entry compression: The ZipEntry for a nested jar must be saved by using the ZipEntry.STORED method. This is required so that we can seek directly to individual content within the nested jar. The content of the nested jar file itself can still be compressed, as can any other entries in the outer jar.

System classLoader: Launched applications should use Thread.getContextClassLoader() when loading classes (most libraries and frameworks do so by default). Trying to load nested jar classes with ClassLoader.getSystemClassLoader() fails. java.util.Logging always uses the system classloader. For this reason, you should

	Tip
	Repackaged archives do not contain devtools by default. If you want to use a certain remote devtools feature, you need to disable the `excludeDevtools` build property to include it. The property is supported with both the Maven and Gradle plugins.

	Tip
	For a complete list of the properties that are applied by the devtools, see DevToolsPropertyDefaultsPostProcessor.

	Note
	As long as forking is enabled, you can also start your application by using the supported build plugins (Maven and Gradle), since DevTools needs an isolated application classloader to operate properly. By default, Gradle and Maven do that when they detect DevTools on the classpath.

	Tip
	Automatic restart works very well when used with LiveReload. See the LiveReload section for details. If you use JRebel, automatic restarts are disabled in favor of dynamic class reloading. Other devtools features (such as LiveReload and property overrides) can still be used.

	Note
	DevTools relies on the application context’s shutdown hook to close it during a restart. It does not work correctly if you have disabled the shutdown hook (`SpringApplication.setRegisterShutdownHook(false)`).

	Note
	When deciding if an entry on the classpath should trigger a restart when it changes, DevTools automatically ignores projects named `spring-boot`, `spring-boot-devtools`, `spring-boot-autoconfigure`, `spring-boot-actuator`, and `spring-boot-starter`.

	Note
	DevTools needs to customize the `ResourceLoader` used by the `ApplicationContext`. If your application provides one already, it is going to be wrapped. Direct override of the `getResource` method on the `ApplicationContext` is not supported.

	Tip
	If you want to keep those defaults and add additional exclusions, use the `spring.devtools.restart.additional-exclude` property instead.

	Tip
	You might want to set `spring.devtools.restart.trigger-file` as a global setting, so that all your projects behave in the same way.

	Note
	All property keys must be unique. As long as a property starts with `restart.include.` or `restart.exclude.` it is considered.

	Tip
	All `META-INF/spring-devtools.properties` from the classpath will be loaded. You can package files inside your project, or in the libraries that the project consumes.

	Note
	You can only run one LiveReload server at a time. Before starting your application, ensure that no other LiveReload servers are running. If you start multiple applications from your IDE, only the first has LiveReload support.

	Warning
	Enabling `spring-boot-devtools` on a remote application is a security risk. You should never enable support on a production deployment.

	Note
	Because the remote client is using the same classpath as the real application it can directly read application properties. This is how the `spring.devtools.remote.secret` property is read and passed to the server for authentication.

	Tip
	It is always advisable to use `https://` as the connection protocol, so that traffic is encrypted and passwords cannot be intercepted.

	Tip
	If you need to use a proxy to access the remote application, configure the `spring.devtools.remote.proxy.host` and `spring.devtools.remote.proxy.port` properties.

	Note
	Files are only monitored when the remote client is running. If you change a file before starting the remote client, it is not pushed to the remote server.

	Note
	When setting `JAVA_OPTS` on Microsoft Windows, make sure to quote the entire instruction, such as `set "JAVA_OPTS=-Xms256m -Xmx2048m"`. Doing so ensures the values are properly passed to the process.

Items	Grabs
`JdbcTemplate`, `NamedParameterJdbcTemplate`, `DataSource`	JDBC Application.
`@EnableJms`	JMS Application.
`@EnableCaching`	Caching abstraction.
`@Test`	JUnit.
`@EnableRabbit`	RabbitMQ.
`@EnableReactor`	Project Reactor.
extends `Specification`	Spock test.
`@EnableBatchProcessing`	Spring Batch.
`@MessageEndpoint` `@EnableIntegrationPatterns`	Spring Integration.
`@Controller` `@RestController` `@EnableWebMvc`	Spring MVC + Embedded Tomcat.
`@EnableWebSecurity`	Spring Security.
`@EnableTransactionManagement`	Spring Transaction Management.

	Tip
	See subclasses of `CompilerAutoConfiguration` in the Spring Boot CLI source code to understand exactly how customizations are applied.

	Tip
	Many Spring annotations work without using `import` statements. Try running your application to see what fails before adding imports.