在spring mvc3.2及以上版本增加了对请求的异步处理，是在servlet3的基础上进行封装的。
1、修改web.xml
<?xml version="1.0" encoding="UTF-8"?><web-app version="3.0" xmlns="/xml/ns/javaee"xmlns:xsi="/2001/XMLSchema-instance"xsi:schemaLocation="/xml/ns/javaee /xml/ns/javaee/web-app_3_0.xsd">...</web-app>
1.1、声明version="3.0"，声明web-app_3_0.xsd
1.2、为servlet或者filter设置启用异步支持：<async-supported>true</async-supported>，修改WEB应用的web.xml
<!-- spring mvc --><servlet><servlet-name>SpringMvc</servlet-name><servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class><init-param><param-name>contextConfigLocation</param-name><param-value>...</param-value></init-param><load-on-startup>1</load-on-startup><async-supported>true</async-supported></servlet>
2、使controller类支持async
2.1、返回java.util.concurrent.Callable来完成异步处理
package org.springframework.samples.mvc.async;import java.util.concurrent.Callable;import org.springframework.stereotype.Controller;import org.springframework.ui.Model;import org.springframework.web.bind.annotation.ExceptionHandler;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestParam;import org.springframework.web.bind.annotation.ResponseBody;import org.springframework.web.context.request.async.WebAsyncTask;@Controller@RequestMapping("/async/callable")public class CallableController {@RequestMapping("/response-body")public @ResponseBody Callable<String> callable() {return new Callable<String>() {@Overridepublic String call() throws Exception {Thread.sleep(2000);return "Callable result";}};}@RequestMapping("/view")public Callable<String> callableWithView(final Model model) {return new Callable<String>() {@Overridepublic String call() throws Exception {Thread.sleep(2000);model.addAttribute("foo", "bar");model.addAttribute("fruit", "apple");return "views/html";}};}@RequestMapping("/exception")public @ResponseBody Callable<String> callableWithException(final @RequestParam(required=false, defaultValue="true") boolean handled) {return new Callable<String>() {@Overridepublic String call() throws Exception {Thread.sleep(2000);if (handled) {// see handleException method further belowthrow new IllegalStateException("Callable error");}else {throw new IllegalArgumentException("Callable error");}}};}@RequestMapping("/custom-timeout-handling")public @ResponseBody WebAsyncTask<String> callableWithCustomTimeoutHandling() {Callable<String> callable = new Callable<String>() {@Overridepublic String call() throws Exception {Thread.sleep(2000);return "Callable result";}};return new WebAsyncTask<String>(1000, callable);}@ExceptionHandler@ResponseBodypublic String handleException(IllegalStateException ex) {return "Handled exception: " + ex.getMessage();}}
2.2、在异步处理完成时返回org.springframework.web.context.request.async.DeferredResult其他线程，例如一个JMS或一个AMQP消息,Redis通知等等：
@RequestMapping("/quotes")@ResponseBodypublic DeferredResult<String> quotes() {DeferredResult<String> deferredResult = new DeferredResult<String>();// Add deferredResult to a Queue or a Map...return deferredResult;}// In some other thread...deferredResult.setResult(data);// Remove deferredResult from the Queue or Map
3、spring配置文件的修改
spring mvc的dtd的声明必须大于等于3.2
<mvc:annotation-driven><!-- 可不设置，使用默认的超时时间 --><mvc:async-support default-timeout="3000"/></mvc:annotation-driven>
实际使用示例：
function deferred(){$.get('quotes.htm',function(data){console.log(data);deferred();//每次请求完成,再发一次请求,避免客户端定时刷新来获取数据 });}
这么做的好处避免web server的连接池被长期占用而引起性能问题，调用后生成一个非web的服务线程来处理，增加web服务器的吞吐量~~
可以看下这个blog，还不错：/blog/2215852
