使用DWR反转实现信息推送（一）

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DWR 反转推送

除了利用Pushlet实现信息推送外，DWR反转同样可以实现推送。

DWR的简单配置方法已经在以前的博客中写过。所以这里直接贴代码：

新建web工程，这里命名为DwrEg，包结构如下：

web.xml代码如下：

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
	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_2_5.xsd">
  <servlet>
      <servlet-name>dwr-invoke</servlet-name>
      <servlet-class>uk.ltd.getahead.dwr.DWRServlet</servlet-class>
     <init-param>
         <param-name>debug</param-name>
         <param-value>true</param-value> 
     </init-param>
     <init-param>
         <param-name>activeReverseAjaxEnabled</param-name>
		 <param-value>true</param-value>
     </init-param>  
     <!-- 
     <init-param>
         <param-name>classes</param-name>
         <param-value>java.lang.Object</param-value>
        </init-param> -->
  </servlet>

  <servlet-mapping>
     <servlet-name>dwr-invoke</servlet-name>
     <url-pattern>/dwr/*</url-pattern>
  </servlet-mapping>
  <welcome-file-list>
    <welcome-file>client.html</welcome-file>
  </welcome-file-list>
</web-app>

dwr.xml代码如下：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE dwr PUBLIC "-//GetAhead Limited//DTD Direct Web Remoting 2.0//EN" "http://getahead.org/dwr//dwr20.dtd">
<dwr>
    <allow> 
		<create javascript="myrevsrse" creator="new">
			<param name="class" value="com.src.MyReverse"/>
		</create>
   </allow>
</dwr>

MyReverse.java代码如下：

package com.src;

import java.util.Collection;

import org.directwebremoting.ScriptBuffer;
import org.directwebremoting.ScriptSession;
import org.directwebremoting.ServerContext;
import org.directwebremoting.ServerContextFactory;
import org.directwebremoting.WebContext;
import org.directwebremoting.WebContextFactory;
import org.directwebremoting.proxy.dwr.Util;

public class MyReverse {
	public void sendMes(String mes){
		System.out.println("kao shi si bestllll...");
		send("系统消息："+mes);
	}
	public void send(final String output) {
		org.directwebremoting.WebContext web = WebContextFactory.get();  
		String page = web.getServletContext().getContextPath()+"/client.html"; 
		
		Collection sessions = web.getScriptSessionsByPage(page);   
		System.out.println("size=="+sessions.size());
		 
		Util utilAll = new Util(sessions);  
	  
	    utilAll.addFunctionCall("callBack", output); //callBack是client.jsp里面的javascript函数，output是传递过去的参数
	    //utilAll.setValue("news_id", output, false);   
	    //这种方法也可以，直接将client.html里id为news_id的textarea的值设置为output的值     
	}

	public void noticeNewOrder(int id) {
        WebContext wctx = WebContextFactory.get();
        ScriptBuffer script = new ScriptBuffer();
        script.appendScript("receiveMessages(")
                .appendData(id)
                .appendScript(");");

        ServerContext sctx = ServerContextFactory.get(wctx.getServletContext());
        Collection<ScriptSession> pages = sctx.getScriptSessionsByPage("/DwrEg/client.html");
        
        for (ScriptSession session : pages) {
            session.addScript(script);
        }
    }
}

client.html代码如下：

<html>
<script type="text/javascript" src="dwr/engine.js"></script>
<script type="text/javascript" src="dwr/util.js"></script>
<head>
<script type="text/javascript">

	function callBack(data){    
           alert(data);   
        }  
	function receiveMessages(id) {
            $('orderNotice').innerHTML = "收到id为" + id + "的新订单!";
            $('orderNotice').show();
        }
   
</script>
</head>
<body onload="dwr.engine.setActiveReverseAjax(true);">
<textarea rows="20" cols="20" id="news_id"></textarea>
<br /> 
<div id="orderNotice"></div> 
</body>
</html>

推送界面dopush.html的代码如下：

<html>
<script type="text/javascript" src="dwr/engine.js"></script>
<script type="text/javascript" src="dwr/util.js"></script>
<script type="text/javascript" src="dwr/interface/myrevsrse.js"></script>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
<script type="text/javascript">
	function sendnews(){ 
		var new_content = dwr.util.getValue("newcontent");
		myrevsrse.sendMes(new_content);
	}
	
	function sendinfo(){ 
	   myrevsrse.noticeNewOrder(12);
	}  
</script>
</head>
<body>
<input type="text" name="newcontent">
<input type = "button" value="发消息" onclick="sendnews()"/> 
<br />
<input type = "button" value="send 2" onclick="sendinfo()"/>
<br />  
</body>

同样，这里的问题也是怎么实现点对点的信息推送，这儿只是实现了向所有的clent.html页面推送信息，以后接着总结。。。。