pushlet 之 Pushlet使用手把手实例

Pushlet（一种comet 架构的实现）是基于Servlet 机制，数据从server端的Java 对象直接推送（push）

到客户端浏览器的（动态）HTML 页面，而无需任何Java applet 或者插件的帮助。

在MyEclipse中创建工程。附件包含了从官方下载的Pushlet包已经本次的源码包，直接导入到开发工具即可。
在创建的工程中增加pushlet.jar，log4j.jar。拷贝pushlet.properties，sources.properties到WEB-INF下。
拷贝ajax-pushlet-client.js到WebRoot下。
配置web.xml

Xml代码

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
<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>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app
    PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
    "http://java.sun.com/dtd/web-app_2_3.dtd">
<!-- $Id: web.xml,v 1.7 2005/02/21 17:21:49 justb Exp $ -->
<web-app>
	<!-- Define the pushlet servlet -->
	<servlet>
		<servlet-name>pushlet</servlet-name>
		<servlet-class>nl.justobjects.pushlet.servlet.Pushlet</servlet-class>
		<load-on-startup>3</load-on-startup>
	</servlet>
	<!-- Define the Servlet Mappings. -->
	<!-- The pushlet -->
	<servlet-mapping>
		<servlet-name>pushlet</servlet-name>
		<url-pattern>/pushlet.srv</url-pattern>
	</servlet-mapping>
</web-app>

后台代码HelloWorldPlushlet.java，该类包含一个内部类

Java代码

package com;
import nl.justobjects.pushlet.core.Event;
import nl.justobjects.pushlet.core.EventPullSource;
public class HelloWorldPlushlet {
static public class HwPlushlet extends EventPullSource {
// 休眠五秒
@Override
protected long getSleepTime() {
return 5000;
}
@Override
protected Event pullEvent() {
Event event = Event.createDataEvent("/cuige/he");
event.setField("mess", "hello,world!Plushlet!");
return event;
}
}
}

package com;
import nl.justobjects.pushlet.core.Event;
import nl.justobjects.pushlet.core.EventPullSource;
public class HelloWorldPlushlet {	
	static public class HwPlushlet extends EventPullSource {
		// 休眠五秒
		@Override
		protected long getSleepTime() {
			return 5000;
		}
		@Override
		protected Event pullEvent() {
			Event event = Event.createDataEvent("/cuige/he");
			event.setField("mess", "hello,world!Plushlet!");
			return event;
		}
	}
}

sources.properties清理其他，定义自己发布的内容

Java代码

source1=com.HelloWorldPlushlet$HwPlushlet

source1=com.HelloWorldPlushlet$HwPlushlet

在JSP中调用

Jsp代码

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta http-equiv="Pragma" content="no-cache" />
<script type="text/javascript" src="ajax-pushlet-client.js"></script>
<script type="text/javascript">
PL._init();
PL.joinListen('/cuige/he');
function onData(event) {
alert(event.get("mess"));
// 离开
// PL.leave();
}
</script>
</head>
<body>
<center>
<h1>
my first pushlet!
</h1>
</center>
</body>
</html>

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<html>
	<head>
		<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
		<meta http-equiv="Pragma" content="no-cache" />
		<script type="text/javascript" src="ajax-pushlet-client.js"></script>		
		<script type="text/javascript">
			PL._init(); 
			PL.joinListen('/cuige/he');
			function onData(event) { 
				alert(event.get("mess")); 
				// 离开
				// PL.leave();
			}
		</script>
	</head>
	<body>
		<center>
		<h1>
			my first pushlet!
		</h1>
		</center>
	</body>
</html>

将工程部署到Tomcat后访问，该页面以五秒钟一个间隔，收到后台传来的数据！

工程部署后如下图展示

每次访问时，后台都会打印增加到管理中的用户信息，当关闭浏览器后，服务器会在超时后自动清理！