- Servlet 3开始支持异步请求处理
- Spring MVC 3.2开始支持Servlet3的这项特性
- controller可以从另外一个线程返回一个
java.util.concurrent.Callable,而不是一个简单的值- 此时Servlet容器线程已经释放,可以处理其他的请求
- Spring MVC通过借助
TaskExecutor调起另外一个线程(例子中的mvcTaskExecutor)
- controller也可以从另外一个线程返回一个
DeferredResult- 此时,Spring MVC并不知道这个线程的存在
- 比如一个定时任务
10.2 演示
-
在
05点睛Spring MVC 4.1-服务器端推送中,我们也演示了通过SSE实现长连接- 但在IE的一些版本是不支持的
-
本例通过Spring MVC对异步处理的支持来演示长连接的支持,即服务器端推送
- 支持所有浏览器
-
Servlet开启异步支持
package com.wisely;import javax.servlet.ServletContext;import javax.servlet.ServletException;import javax.servlet.ServletRegistration.Dynamic;import org.springframework.web.WebApplicationInitializer;import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;import org.springframework.web.servlet.DispatcherServlet;public class WebInitializer implements WebApplicationInitializer { @Override public void onStartup(ServletContext servletContext) throws ServletException { AnnotationConfigWebApplicationContext ctx = new AnnotationConfigWebApplicationContext(); ctx.register(DemoMVCConfig.class); //注册spring mvc的DispatcherServlet ctx.setServletContext(servletContext); Dynamic servlet = servletContext.addServlet("dispatcher", new DispatcherServlet(ctx)); servlet.addMapping("/"); servlet.setLoadOnStartup(1); servlet.setAsyncSupported(true);//此句开启 }} DeferredResult所需的定时处理
package com.wisely.service;import org.springframework.scheduling.annotation.Scheduled;import org.springframework.stereotype.Service;import org.springframework.web.context.request.async.DeferredResult;@Servicepublic class AysncService { private DeferredResult deferredResult; public DeferredResult getAsyncUpdate() { deferredResult = new DeferredResult (); return deferredResult; } @Scheduled(fixedDelay = 5000) public void refresh() { if (deferredResult != null) { deferredResult.setResult(new Long(System.currentTimeMillis()) .toString()); } }} - 开启Spring MVC支持配置：继承
WebMvcConfigurerAdapter的配置类DemoMVCConfig
@Override public void configureAsyncSupport(AsyncSupportConfigurer configurer) { configurer.setDefaultTimeout(30*1000L); //tomcat默认10秒 configurer.setTaskExecutor(mvcTaskExecutor());//所借助的TaskExecutor } @Bean public ThreadPoolTaskExecutor mvcTaskExecutor(){ ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor(); executor.setCorePoolSize(10); executor.setQueueCapacity(100); executor.setMaxPoolSize(25); return executor; } @Override public void addViewControllers(ViewControllerRegistry registry) { registry.addViewController("/async").setViewName("/async"); } - 测试控制器
package com.wisely.web;import java.util.concurrent.Callable;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.ResponseBody;import org.springframework.web.context.request.async.DeferredResult;import com.wisely.service.AysncService;@Controllerpublic class AysncController { @Autowired AysncService aysncService; @RequestMapping("/call") @ResponseBody public Callable asyncCall() { //借助mvcTaskExecutor在另外一个线程调用 //此时Servlet容器线程已经释放,可以处理其他的请求 return new Callable () { @Override public String call() throws Exception { Thread.sleep(3000); return "Async Hello World"; } }; } @RequestMapping("/defer") @ResponseBody public DeferredResult deferredCall() { //调用aysncService的getAsyncUpdate方法 //deferredResult被计划任务每五秒钟更新一次 return aysncService.getAsyncUpdate(); }} - 测试页面
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %><%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> Insert title here "> -
测试
- 访问http://localhost:8080/testSpringMVC/async
- 点击call
- 点击defer