实现功能：sendMsg.jsp发送一个消息到后台，后台将消息推送到showMsg.jsp页面。
1、web.xml 配置，在web.xml里面添加如下内容：
<!-- 使用DWR进行页面消息推送 --> <servlet> <display-name>DWR Servlet</display-name> <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> <!-- 使用polling和comet的方式 --> <init-param> <param-name>pollAndCometEnabled</param-name> <param-value>true</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>dwr-invoker</servlet-name> <url-pattern>/dwr/*</url-pattern> </servlet-mapping>
<!DOCTYPE dwr PUBLIC
"-//GetAhead Limited//DTD Direct Web Remoting 3.0//EN"
"http://getahead.org/dwr/dwr30.dtd">
<dwr>
<allow>
<!-- 这里的javascript 值就是页面引用的第三个js文件的名称-->
<create creator="new" javascript="SendMsg">
<param name="class">iwco.dwrs.SendMsg</param>
</create>
</allow>
</dwr>
3、java类 SendMsg.java
package iwco.dwrs;
import java.util.Collection;
import org.directwebremoting.ScriptBuffer;
import org.directwebremoting.ScriptSession;
import org.directwebremoting.WebContext;
import org.directwebremoting.WebContextFactory;
import org.directwebremoting.proxy.dwr.Util;
public class SendMsg {
@SuppressWarnings("deprecation")
public void sendMsg(String msg){
//得到上下文
WebContext contex = WebContextFactory.get();
//得到要推送到 的页面 dwr3为项目名称 ， 一定要加上。
Collection<ScriptSession> sessions = contex.getScriptSessionsByPage("/dwrTest/showMsg.jsp");
//不知道该怎么解释这个 ，
Util util = new Util(sessions);
//下面是创建一个javascript脚本 ， 相当于在页面脚本中添加了一句 show(msg);
ScriptBuffer sb = new ScriptBuffer();
sb.appendScript("show(");
sb.appendData(msg);
sb.appendScript(")");
//推送
util.addScript(sb);
}
}
sendMsg.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
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>sendMsg.jsp</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">
<script type="text/javascript" src="/dwrTest/dwr/util.js"></script>
<script type="text/javascript" src="/dwrTest/dwr/engine.js"></script>
<script type="text/javascript" src="/dwrTest/dwr/interface/SendMsg.js"></script>
<script type="text/javascript" src="/dwrTest/js/jquery.min.js"></script>
<script type="text/javascript">
$(function(){
dwr.engine.setActiveReverseAjax(true);
$("#but").click(function(){
SendMsg.sendMsg($("#msg").val());
});
});
</script>
</head>
<body>
<input type="text" id="msg" />
<input type="button" value="发送" id="but" />
</body>
</html>
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
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>showMsg</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">
<script type="text/javascript" src="/dwrTest/dwr/util.js"></script>
<script type="text/javascript" src="/dwrTest/dwr/engine.js"></script>
<script type="text/javascript" src="/dwrTest/dwr/interface/SendMsg.js"></script>
<script type="text/javascript" src="/dwrTest/js/jquery.min.js"></script>
<script type="text/javascript">
$(function(){
//这句话千万不能少 ，表示允许使用推送技术
dwr.engine.setActiveReverseAjax(true);
});
//这个函数是提供给后台推送的时候 调用的
function show(msg){
$("#message").text(msg);
}
</script>
</head>
<body>
<div id="message" style="width: 200px;height: 200px;border: 1px solid red ; text-align: center; padding: 5px;"></div>
</body>
</html>
原文：http://blog.csdn.net/zhao50632/article/details/42672237