序
之前寫過(guò)一篇文章：springmvc不斷輸出文本到網(wǎng)頁(yè)，采用的是對(duì)response不斷進(jìn)行write和flush實(shí)現(xiàn)的。在spring 4.2版本的時(shí)候提供了一個(gè)SseEmitter可以直接用來(lái)實(shí)現(xiàn)這個(gè)功能。
實(shí)例
@Controller
@RequestMapping("/sse")
public class SseEmitterController {
private static final Logger LOGGER = LoggerFactory.getLogger(SseEmitterController.class);
@Autowired
@Qualifier("mvcTaskExecutor")
ThreadPoolTaskExecutor mvcTaskExecutor;
@GetMapping("")
public SseEmitter sseDemo() throws InterruptedException {
final SseEmitter emitter = new SseEmitter(0L); //timeout設(shè)置為0表示不超時(shí)
mvcTaskExecutor.execute(() -> {
try {
for(int i=0;i<100;i++){
emitter.send("hello"+i);
LOGGER.info("emit:{}","hello"+i);
Thread.sleep(1000*1);
}
emitter.complete();
} catch (Exception e) {
emitter.completeWithError(e);
}
});
return emitter;
}
}
輸出實(shí)例
data:"hello0"
data:"hello1"
data:"hello2"
data:"hello3"
data:"hello4"
data:"hello5"
//......
注意事項(xiàng)
- 這里的SseEmitter的send不能阻塞mvc線程，必須提前返回，然后把send放到異步里頭
除了使用上述的放入線程池的方式，也可以直接調(diào)用標(biāo)記有async的方法
- 這里SseEmitter的timeout設(shè)置為0，表示不超時(shí).
如果不設(shè)置為0，那么如果SseEmitter在指定的時(shí)間（AsyncSupportConfigurer設(shè)置的timeout,默認(rèn)為30秒)未完成會(huì)拋出異常
org.springframework.web.context.request.async.AsyncRequestTimeoutException: null
at org.springframework.web.context.request.async.TimeoutDeferredResultProcessingInterceptor.handleTimeout(TimeoutDeferredResultProcessingInterceptor.java:42) ~[spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
at org.springframework.web.context.request.async.DeferredResultInterceptorChain.triggerAfterTimeout(DeferredResultInterceptorChain.java:75) ~[spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
at org.springframework.web.context.request.async.WebAsyncManager$5.run(WebAsyncManager.java:392) ~[spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
at org.springframework.web.context.request.async.StandardServletAsyncWebRequest.onTimeout(StandardServletAsyncWebRequest.java:143) ~[spring-web-4.3.10.RELEASE.jar:4.3.10.RELEASE]
at org.apache.catalina.core.AsyncListenerWrapper.fireOnTimeout(AsyncListenerWrapper.java:44) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
at org.apache.catalina.core.AsyncContextImpl.timeout(AsyncContextImpl.java:134) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
at org.apache.catalina.connector.CoyoteAdapter.asyncDispatch(CoyoteAdapter.java:153) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
at org.apache.coyote.AbstractProcessor.dispatch(AbstractProcessor.java:224) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:53) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1455) ~[tomcat-embed-core-8.5.16.jar:8.5.16]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.16.jar:8.5.16]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_71]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_71]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.16.jar:8.5.16]
at java.lang.Thread.run(Thread.java:745) [na:1.8.0_71]
小結(jié)
SseEmitter在運(yùn)行比較耗時(shí)的任務(wù)時(shí)非常好用，比如實(shí)時(shí)查看部署進(jìn)度，比如查看定時(shí)任務(wù)的實(shí)時(shí)輸出等。
