詳解spring mvc對異步請求的處理

在spring mvc3.2及以上版本增加了對請求的異步處理，是在servlet3的基礎上進行封裝的。

1、修改web.xml

 <?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、聲明version="3.0"，聲明web-app_3_0.xsd

1.2、為servlet或者filter設置啟用異步支持： <async-supported>true</async-supported> ，修改WEB應用的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類支持async

2.1、返回java.util.concurrent.Callable來完成異步處理

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>() { @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、在異步處理完成時返回org.springframework.web.context.request.async.DeferredResult其他線程，例如一個JMS或一個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的聲明必須大於等於3.2

 <mvc:annotation-driven><!-- 可不設置，使用默認的超時時間--> <mvc:async-support default-timeout="3000"/></mvc:annotation-driven>

實際使用示例：

 function deferred(){ $.get('quotes.htm',function(data){ console.log(data); deferred();//每次請求完成,再發一次請求,避免客戶端定時刷新來獲取數據});}

這麼做的好處避免web server的連接池被長期佔用而引起性能問題，調用後生成一個非web的服務線程來處理，增加web服務器的吞吐量~~

以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持武林網。