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
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<?xml version="1.0" encoding="UTF-8"?><web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/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
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<!-- 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
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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>() { @Override public String call() throws Exception { Thread.sleep(2000); return "Callable result"; } }; } @RequestMapping("/view") public Callable<String> callableWithView(final Model model) { return new Callable<String>() { @Override public 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>() { @Override public String call() throws Exception { Thread.sleep(2000); if (handled) { // see handleException method further below throw 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>() { @Override public String call() throws Exception { Thread.sleep(2000); return "Callable result"; } }; return new WebAsyncTask<String>(1000, callable); } @ExceptionHandler @ResponseBody public 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：
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@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
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<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：
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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~~
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持服务器之家。
原文链接：http://www.cnblogs.com/yangzhilong/p/3725128.html
