DWR框架：direct web remoting的缩写；
它是一个远程服务器端的Ajax开源框架，其能改善web界面与java类的交互。它可以允许在浏览器里的代码使用运行在WEB服务器上的JAVA函数，就像它就在浏览器里一样。
1.新建web工程：
2.导入jar包：引入dwr.jar和commons-logging-1.1.3.jar
3.在web.xml中加入dwr使用功能
<servlet>
<servlet-name> dwr-invoker </servlet-name>
<servlet-class> org.directwebremoting.servlet.DwrServlet</servlet-class >
<init-param>
<param-name> debug</param-name >
<param-value> true</param-value >
</init-param>
<init-param>
<param-name> crossDomainSessionSecurity</param-name >
<param-value> false</param-value >
</init-param>
<init-param>
<param-name> allowScriptTagRemoting</param-name >
<param-value> true</param-value >
</init-param>
</servlet>
<servlet-mapping>
<servlet-name> dwr-invoker </servlet-name>
<url-pattern>/dwr/*</url-pattern>
</servlet-mapping>
4.在src下新建MessagePush类
package com.DWR.dwr;
public class MessagePush {
public void sendMessage(){
System.out.println("dwr success!");
}
}
5.在web.xml同一目录下新建dwr.xml配置js函数与java类的映射关系。
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE dwr PUBLIC
"-//GetAhead Limited//DTD Direct Web Remoting 1.0//EN"
"http://www.getahead.ltd.uk/dwr/dwr30.dtd">
<dwr>
<allow>
<create creator="new" javascript="MessagePush">
<param name="class" value="com.trigo.biz.MessagePush"/>
</create>
</allow>
</dwr>
6.在index.jsp中写入js逻辑（该处使用到jquery，请自行添加）：
<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'index.jsp' starting page</title>
<Meta http-equiv="pragma" content="no-cache">
<Meta http-equiv="cache-control" content="no-cache">
<Meta http-equiv="expires" content="0">
<Meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<Meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
<script src="jquery-1.7.js"></script>
<script type= "text/javascript" src ="dwr/util.js"></script>
<script type="text/javascript" src= "dwr/engine.js"></script >
<script type="text/javascript" src= "dwr/interface/messagePush.js" ></script>
<script>
$('document').ready(function(){
messagePush.sendMessage();
});
</script>
</head>
<body>
This is my JSP page. <br>
</body>
</html>
说明：jsp文件中必须引入几个js,它们都是隐含存在的，不用考虑它们在哪儿。其中engine.js和util.js是固定的。另外的一个js的名称就是dwr.xml中配置的类名。
