pushlet_向在线的特定用户发送消息的单线程应用

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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:

	pushlet_userId
	
		index.html
		index.htm
		index.jsp
		default.html
		default.htm
		default.jsp
	
	
		pushlet
		nl.justobjects.pushlet.servlet.Pushlet
		3
	
	
		pushlet
		/pushlet.srv
	

 

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"%>









	

 

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 

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