dwr进行页面推送简单实例

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>

2、配置dwr.xml

<!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);  
	    }  
}

4、页面

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>

showMsg.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>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,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>

dwr进行页面推送简单实例

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