pushlet_向在线的特定用户发送消息的单线程应用-优快云博客

本文介绍如何使用Pushlet框架实现Web应用中的实时双向通信。包括配置项目结构、修改关键文件如web.xml和ajax-pushlet-client.js，以及创建推送类等步骤。

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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:

<?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: