准备

web项目中引入comet4j.js文件和comet4j-tomcat7.jar包

web.xml

修改web.xml，添加以下comet配置

<listener>
        <listener-class>org.comet4j.core.CometAppListener</listener-class>
    </listener>
    <listener>
        <description>HelloWorld</description>
        <listener-class>com.aerors.listener.TestComet</listener-class>
    </listener>
    <servlet>
        <display-name>CometServlet</display-name>
        <servlet-name>CometServlet</servlet-name>
        <servlet-class>org.comet4j.core.CometServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>CometServlet</servlet-name>
        <url-pattern>/conn</url-pattern>
    </servlet-mapping>

com.aerors.listener.TestComet改为实际java类位置

com.aerors.listener.TestComet

package com.aerors.listener;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

import org.comet4j.core.CometContext;
import org.comet4j.core.CometEngine;
 
public class TestComet implements ServletContextListener {

    private static final String CHANNEL = "test";
    private static int number1 = 0 ;

    public void contextInitialized(ServletContextEvent arg0) {
        CometContext cc = CometContext.getInstance();
        cc.registChannel(CHANNEL);// 注册应用的channel

        Thread helloAppModule = new Thread(new HelloAppModule(),
                "Sender App Module");
        // 是否启动
        helloAppModule.setDaemon(true);
        // 启动线程
        helloAppModule.start();
    }

    class HelloAppModule implements Runnable {
        public void run() {
            while (true) {
                try {
                    // 睡眠时间
                    Thread.sleep(2000);
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
                CometEngine engine = CometContext.getInstance().getEngine();
                // 获取消息内容
                long l = getFreeMemory();
                // 开始发送         
                engine.sendToAll(CHANNEL, number1++);
            }
        }
    }
}

前台页面JSP页面

<%@ 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 XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">  
<html xmlns="http://www.w3.org/1999/xhtml">  
<head>  
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />  
<title>Comet4J Hello World</title> 
<script type="text/javascript" src="js/libs/jquery/jquery.min.js"></script> 
<script type="text/javascript" src="js/libs/comet4j/comet4j.js"></script>
<script type="text/javascript">  
function init(){  
        var kbDom = document.getElementById('kb');   
        JS.Engine.on({  
                test : function(aa){//侦听一个channel  
                        kbDom.innerHTML = aa; 
                        console.log(aa);
                }  
        }); 
        JS.Engine.start('conn'); 
        JS.Engine.on(
            'test',function(cId,channelList,engine){
                  console.dir('连接已建立，连接ID为：' + cId);
            });
         
}  
function test(){
    var kbDom = document.getElementById('kb');  
 
    JS.Engine.start('conn'); 
    JS.Engine.on({  
            test : function(aa){//侦听一个channel  
                    kbDom.innerHTML = aa; 
                    console.log(aa);
            } 
    }); 
}
</script>  
</head>  
<body onload="init();">  
    <span id="kb">...</span> <br/>  
    <button onclick="test();">click</button>
</body>  
</html>

两种方式加载都可以