项目里面有比较多的导入导出，录音文件加载等功能，但是有个问题是：导入导出客户端可能会频繁的点击，录音文件一次性可能会加载多个。如果导出的excel文件过大，或者加载的录音文件过多，或者一个音频文件过长，可能会出现 这个异常：

org.apache.catalina.connector.ClientAbortException: java.io.IOException: APR error: -32
	at org.apache.catalina.connector.OutputBuffer.realWriteBytes(OutputBuffer.java:396)
	at org.apache.tomcat.util.buf.ByteChunk.append(ByteChunk.java:344)
	at org.apache.catalina.connector.OutputBuffer.writeBytes(OutputBuffer.java:421)
	at org.apache.catalina.connector.OutputBuffer.write(OutputBuffer.java:409)
	at org.apache.catalina.connector.CoyoteOutputStream.write(CoyoteOutputStream.java:97)
	at java.io.BufferedOutputStream.write(BufferedOutputStream.java:122)
	at java.io.FilterOutputStream.write(FilterOutputStream.java:97)
	at com.zhuanche.serv.punish.DriverPunishClientService.renderVideo(DriverPunishClientService.java:181)
	at com.zhuanche.controller.driver.DriverPunishController.render(DriverPunishController.java:138)
	at com.zhuanche.controller.driver.DriverPunishController$$FastClassBySpringCGLIB$$1182fa42.invoke(<generated>)
	at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:738)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
	at org.apache.shiro.spring.security.interceptor.AopAllianceAnnotationsAuthorizingMethodInterceptor$1.proceed(AopAllianceAnnotationsAuthorizingMethodInterceptor.java:82)
	at org.apache.shiro.authz.aop.AuthorizingMethodInterceptor.invoke(AuthorizingMethodInterceptor.java:39)
	at org.apache.shiro.spring.security.interceptor.AopAllianceAnnotationsAuthorizingMethodInterceptor.invoke(AopAllianceAnnotationsAuthorizingMethodInterceptor.java:115)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:673)
	at com.zhuanche.controller.driver.DriverPunishController$$EnhancerBySpringCGLIB$$fbb8c231.render(<generated>)
	at sun.reflect.GeneratedMethodAccessor2068.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133)
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
　　        这个问题困扰了好久，解决方法有限制过前端的频繁点击的按钮，比如没分钟只允许点击一次，后端有加缓存的限制，比如以用户id+请求条件+请求ip作为key，防止频繁的请求。如果请求频繁，则导出一个空Excel文件以及提示语。但是由于太多地方，仍然会时不时的抛出这个 arp -32的问题。今天想到用异步线程池的方式，参考：
  https://blog.csdn.net/Muscleheng/article/details/81409672  。
  我是采用的注解+@Async方式，但是发现仍然不管用。特别是加载录音文件，还抛出了空指针异常。自己的代码：Controller
    @RequiresPermissions(value = {"punishTripVideo"})
    @RequestMapping("/renderVideo")
    @ResponseBody
    public AjaxResponse render(@RequestParam(name = "filePath") String filePath, HttpServletResponse response) {
        if (StringUtils.isBlank(filePath)) {
            return AjaxResponse.failMsg(RestErrorCode.HTTP_FORBIDDEN, "缺失路径");
        log.info("渲染录音文件, filePath:{}", filePath);
        try {
            driverPunishService.renderVideo(filePath, response);
        } catch (Exception e) {
            log.error("渲染失败",e);
            return AjaxResponse.failMsg(RestErrorCode.HTTP_FORBIDDEN, "渲染失败");
        return AjaxResponse.success(null);
　　service:
     * 渲染行程录音
     * @param filePath
     * @param response
     * @throws IOException
    public void renderVideo(String filePath,HttpServletResponse response) throws IOException {
        log.info("====threadName==== 异步线程池执行该service方法===");
        OutputStream outputStream = null;
        try {
            byte[] fileBytes = OkHttpStreamUtil.executeForBytes(filePath);
            if (Objects.nonNull(fileBytes)) {
                //支持范围请求
                int fileLength = fileBytes.length;
                response.addHeader("Accept-Ranges", "bytes");
                response.addHeader("Content-Length", "" + fileLength);
                response.addHeader("Content-Range", "bytes 0-" + fileLength);
                response.addHeader("Content-Type", "audio/mpeg");
                response.addHeader("Content-Length", "" + fileLength);
                outputStream = new BufferedOutputStream(response.getOutputStream());
                outputStream.write(fileBytes);
                outputStream.flush();
        } catch (IOException io) {
            log.warn("渲染行程录音IOException", io);
        } catch (Exception e) {
            log.error("渲染行程录音失败", e);
            throw e;
        } finally {
            IoUtil.close(outputStream);
  使用异步线程池类：
package com.zhuanche.serv.sync;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
import java.util.concurrent.ThreadPoolExecutor;
 * @author fanht
 * @description 异步线程池
 * @date 2021/1/5 上午9:48
 * @version 1.0
@Configuration
@EnableAsync
public class SyncThreadPool {
    /**核心线程数*/
    private static final Integer CORE_POOL_SIZE = 20;
    /**最大线程数*/
    private static final Integer MAX_POOL_SIZE = 100;
    /**允许线程空闲时间 （单位 秒）*/
    private static final Integer KEEP_ALIVE_TIME  = 10;
    /**缓冲队列大小*/
    private static final Integer QUEUE_CAPACITY  = 200;
    /**线程名前缀  主要是在service层使用*/
    private static final  String THREADNAME_PREFIX  = "Async-service-";
    @Bean("syncTaskExecutor")
    public ThreadPoolTaskExecutor  syncTaskExecutor(){
        ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
        taskExecutor.setCorePoolSize(CORE_POOL_SIZE);
        taskExecutor.setMaxPoolSize(MAX_POOL_SIZE);
        taskExecutor.setKeepAliveSeconds(KEEP_ALIVE_TIME);
        taskExecutor.setQueueCapacity(QUEUE_CAPACITY);
        taskExecutor.setThreadNamePrefix(THREADNAME_PREFIX);
        // 线程池对拒绝任务的处理策略
        // CallerRunsPolicy：由调用线程（提交任务的线程）处理该任务
        taskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
        taskExecutor.initialize();
        return taskExecutor;
   然后在service的方法前面加上@Async("syncTaskExecutor"),发现还是不行。而且抛异常了，问题是由于使用了异步线程池后，controller的线程是 tomcat提供的，而server的是使用的异步线程池。传的outputStream 为空了（详见： https://cloud.tencent.com/developer/article/1511820）
    不过这也给自己了提示：既然是tomcat超时了，那是不是可以通过调整tomcat的超时时间来延长呢？ 我们知道 tomcat的 server.xml的 默认配置是如下：
<Connector port="8080" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8443" />
    会不会是这个默认的超时时间太短了呢？我把时间改成60000试下。