这是SpringMVC提供的一种技术,可以实现服务端向客户端实时推送数据.用法非常简单,只需要在Controller提供一个接口,创建并返回SseEmitter对象,发送数据可以在另一个接口调用其send方法发送数据.这个SseEmitter对象和DeferredResult有异曲同工之妙,只是SseEmitter可以在一次请求中返回多条数据,而DeferredResult只能返回一条.关于DeferredResult的用法请求参考我的另一篇博客: https://www.cnblogs.com/jun1019/p/10807055.html

 1 import org.slf4j.Logger;
 2 import org.slf4j.LoggerFactory;
 3 import org.springframework.web.bind.annotation.RequestMapping;
 4 import org.springframework.web.bind.annotation.RestController;
 5 import org.springframework.web.servlet.mvc.method.annotation.SseEmitter;
 7 import java.io.IOException;
 8 import java.util.Map;
 9 import java.util.concurrent.ConcurrentHashMap;
11 /**
12  * 服务器端实时推送技术之 SseEmitter 的用法测试
13  * <p>
14  * 测试步骤:
15  * 1.请求http://localhost:8888/sse/start?clientId=111接口,浏览器会阻塞,等待服务器返回结果;
16  * 2.请求http://localhost:8888/sse/send?clientId=111接口,可以请求多次,并观察第1步的浏览器返回结果;
17  * 3.请求http://localhost:8888/sse/end?clientId=111接口结束某个请求,第1步的浏览器将结束阻塞;
18  * 其中clientId代表请求的唯一标志;
19  *
20  * @author syj
21  */
22 @RestController
23 @RequestMapping("/sse")
24 public class SseEmitterController {
25     private static final Logger logger = LoggerFactory.getLogger(SseEmitterController.class);
27     // 用于保存每个请求对应的 SseEmitter
28     private Map<String, Result> sseEmitterMap = new ConcurrentHashMap<>();
30     /**
31      * 返回SseEmitter对象
32      *
33      * @param clientId
34      * @return
35      */
36     @RequestMapping("/start")
37     public SseEmitter testSseEmitter(String clientId) {
38         // 默认30秒超时,设置为0L则永不超时
39         SseEmitter sseEmitter = new SseEmitter(0L);
40         sseEmitterMap.put(clientId, new Result(clientId, System.currentTimeMillis(), sseEmitter));
41         return sseEmitter;
42     }
44     /**
45      * 向SseEmitter对象发送数据
46      *
47      * @param clientId
48      * @return
49      */
50     @RequestMapping("/send")
51     public String setSseEmitter(String clientId) {
52         try {
53             Result result = sseEmitterMap.get(clientId);
54             if (result != null && result.sseEmitter != null) {
55                 long timestamp = System.currentTimeMillis();
56                 result.sseEmitter.send(timestamp);
57             }
58         } catch (IOException e) {
59             logger.error("IOException!", e);
60             return "error";
61         }
63         return "Succeed!";
64     }
66     /**
67      * 将SseEmitter对象设置成完成
68      *
69      * @param clientId
70      * @return
71      */
72     @RequestMapping("/end")
73     public String completeSseEmitter(String clientId) {
74         Result result = sseEmitterMap.get(clientId);
75         if (result != null) {
76             sseEmitterMap.remove(clientId);
77             result.sseEmitter.complete();
78         }
79         return "Succeed!";
80     }
82     private class Result {
83         public String clientId;
84         public long timestamp;
85         public SseEmitter sseEmitter;
87         public Result(String clientId, long timestamp, SseEmitter sseEmitter) {
88             this.clientId = clientId;
89             this.timestamp = timestamp;
90             this.sseEmitter = sseEmitter;
91         }
92     }
这个技术有什么用呢? 就看你的想象力了, 比如可以用于和进度有关的操作: 安装进度, 部署进度, 任务执行进度等等.