第一步:
1.新建立web项目,将pushlet目录webapps\pushlet\WEB-INF\classes中的pushlet.properties和sources.properties文件拷贝到src目录下
2.将pushlet目录src中的包拷贝到src目录下
3.上一步添加完后,会出现错误,将log4j的包拷贝到项目的lib目录中就可以了
4.上述步骤完成后,项目的结构如下图所示: 
第二步:
1.修改web.xml文件,添加如下代码:
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0"> <display-name>pushlet_userId</display-name> <welcome-file-list> <welcome-file>index.html</welcome-file> <welcome-file>index.htm</welcome-file> <welcome-file>index.jsp</welcome-file> <welcome-file>default.html</welcome-file> <welcome-file>default.htm</welcome-file> <welcome-file>default.jsp</welcome-file> </welcome-file-list> <servlet> <servlet-name>pushlet</servlet-name> <servlet-class>nl.justobjects.pushlet.servlet.Pushlet</servlet-class> <load-on-startup>3</load-on-startup> </servlet> <servlet-mapping> <servlet-name>pushlet</servlet-name> <url-pattern>/pushlet.srv</url-pattern> </servlet-mapping> </web-app>
2.修改ajax-pushlet-client.js文件,在最开始的位置添加 userId:''属性 , _doRequest函数中的var url = PL.pushletURL + '?p_event=' + anEvent;语句,在后面添加如下代码片段:
if (anEvent == 'join' || anEvent == 'join-listen') {
url = url + '&userId=' + PL.userId;
}
3.修改index.jsp,代码如下所示:
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
<script type="text/javascript" src="ajax-pushlet-client.js"></script>
<script type="text/javascript">
PL.userId = 'twoseven';
PL.joinListen('hwpushlet');
function onData(event) {
document.getElementById("number").innerHTML += event.get("number");
}
</script>
</head>
<body>
<div id="number"></div>
</body>
</html>
4.修改pushlet源代码,找到nl.justobjects.pushlet.core.SessionManager类,修改代码为如下结构:
/**
* Create new Session (but add later).
*/
public Session createSession(Event anEvent) throws PushletException {
// Trivial
//return Session.create(createSessionId());
return Session.create(anEvent.getField("userId", "vistor"));
}
5.添加Pushlet推送类,代码如下:
package com;
import java.util.Random;
import javax.servlet.http.HttpServlet;
import nl.justobjects.pushlet.core.Event;
import nl.justobjects.pushlet.core.EventPullSource;
import nl.justobjects.pushlet.core.Session;
import nl.justobjects.pushlet.core.SessionManager;
public class PushletServ extends HttpServlet {
private static final long serialVersionUID = 1L;
static public class HwPushlet extends EventPullSource {
@Override
protected long getSleepTime() {
return 5000;
}
@Override
protected Event pullEvent() {
Event event = Event.createDataEvent("hwpushlet");
Session[] sessions = SessionManager.getInstance().getSessions();
if (sessions.length > 0) {
StringBuilder str = new StringBuilder("");
for (int i = 0; i < sessions.length; i++) {
if (!sessions[i].getId().equals("twoseven"))
continue;
if (!str.toString().equals(""))
str.append(",");
str.append("'" + sessions[i].getId() + "'");
}
if (!str.toString().equals("")) {
event.setField("number", ""+(new Random().nextInt(10)));//只向userId为twoseven的用户发送信息
}
}
return event;
}
}
}
6.修改sources.properties文件为下图所示:
# Define Pull Sources here. These classes must be derived from # nl.justobjects.pushlet.core.EventPullSource # Inner classes are separated with a $ sign from the outer class. source1=com.PushletServ$HwPushlet
7.启动服务器,在浏览器中输入地址,可以看到如下图所示的结果,第一个红线为服务器返回的结果(动态更新),第二个红线是浏览器的请求:
参考资料:
1.Pushlets官网:http://www.pushlets.com/
2.长连接_百度百科:http://baike.baidu.com/view/2831907.htm
3.利用Ajax实现长连接(模拟推送) (1) - liuhh - 博客园:http://www.cnblogs.com/liuhh/archive/2011/05/12/2044230.html
4.使用 Java 实现 Comet 风格的 Web 应用:http://www.ibm.com/developerworks/cn/web/wa-cometjava/
5.Comet：基于 HTTP 长连接的“服务器推”技术:http://www.ibm.com/developerworks/cn/web/wa-lo-comet/index.html
6.浅析Comet技术在Java Web实时系统开发中的应用:http://syue.com/Paper/Computer/App/245823.html
7.Pushlet 推送数据库消息到前台指定用户:http://blog.csdn.net/dataminer_2007/article/details/7653283