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="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
<!-- 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：
@requestmapping("/quotes")
@responsebody
public 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~~
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