pushlet初次使用心得

最新写项目遇到一个功能，大概需求是用户a 发起任务给用户b，用户b及时提示告知。经过寻找资料，最终考虑使用pushlet。第一次使用先从简单学起，下面写一下初次使用心得：
pushlet百度百科解释： 是一个开源的 Comet 框架，Pushlet 使用了观察者模式：客户端发送请求，订阅感兴趣的事件；服务器端为每个客户端分配一个会话 ID 作为标记，事件源会把新产生的事件以多播的方式发送到订阅者的事件队列里。
工作原理：这位仁兄总结的不错：http://tomyz0223.iteye.com/blog/660738；
下面是我使用的步骤：
首先需要一个jar和一个js文件分别是：
ajax-pushlet-client.js
pushlet.jar

其次配置文件部分：
web.xml部分：

<!-- pushlet --><servlet><servlet-name>pushlet</servlet-name><servlet-class>nl.justobjects.pushlet.servlet.Pushlet</servlet-class><load-on-startup>1</load-on-startup></servlet> <servlet-mapping><servlet-name>pushlet</servlet-name><url-pattern>/pushlet.srv</url-pattern></servlet-mapping>

pushlet.properties 部分：

#
# Pushlet configuration.
# Place this file in the CLASSPATH (e.g. WEB-INF/classes) or directly under WEB-INF.
#
# $Id: pushlet.properties,v 1.13 2007/12/07 12:57:40 justb Exp $
#

#
#
#
config.version=1.0.2

#
# CLASS FACTORY SPECIFICATION
#
# Change these if you want to override any of the core classes
# within the Pushlet framework with your own custom classes.
#
# Examples:
# - custom SessionManager for authorisation
# - maintain lists of active subjects (topics)
# - send events on subscription
# - plug in custom logging like log4j
# Note that you must maintain the semantics of each class !
# Below are the default properties for the core classes.
controller.class=nl.justobjects.pushlet.core.Controller
dispatcher.class=nl.justobjects.pushlet.core.Dispatcher
logger.class=nl.justobjects.pushlet.util.Log4jLogger
# logger.class=nl.justobjects.pushlet.util.DefaultLogger
sessionmanager.class=nl.justobjects.pushlet.core.SessionManager
session.class=nl.justobjects.pushlet.core.Session
subscriber.class=nl.justobjects.pushlet.core.Subscriber
subscription.class=nl.justobjects.pushlet.core.Subscription
sessionmanager.class=com.cisoft.pushlet.MySessionManager
 
# sessionmanager.maxsessions=200

#
# DISPATCHER
#


# TODO: allow properties to be maintained in
# a user dir
# config.redirect=/etc/pushlet.properties

#
# LOGGING
#

# log level (trace(6) debug(5) info (4), warn(3), error(2), fatal(1))
# default is info(4)
log.level=4

#
# LOCAL EVENT SOURCES
#

# should local sources be loaded ?
sources.activate=true

#
# SESSION
#


# algoritm to generate session key:
# values: "randomstring" (default) or "uuid".
# session.id.generation=uuid
session.id.generation=randomstring

# length of generated session key when using "randomstring" generation
session.id.size=10

# Overall session lease time in minutes
# Mainly used for clients that do not perform
# listening, e.g. when publishing only.
session.timeout.mins=5

#
# EVENT QUEUE
#
# Properties for per-client data event queue

# Size for
queue.size=24
queue.read.timeout.millis=20000
queue.write.timeout.millis=20

#
# LISTENING MODE
#

# You may force all clients to use pull mode
# for scalability
listen.force.pull.all=false

#
# Comma-separated list of User Agent substrings.
# Force these browsers to use pull mode, since they
# don't support JS streaming, matching is done using
# String.indexOf() with lowercased agent strings
# use multiple criteria with &.
#
listen.force.pull.agents=safari

#
# PULL MODE
#

# time server should wait on refresing pull client
pull.refresh.timeout.millis=45000

# minimum/maximum wait time client should wait before refreshing
# server provides a random time between these values
pull.refresh.wait.min.millis=2000
pull.refresh.wait.max.millis=6000

#
# POLL MODE
#

# time server should wait on refresing poll client
poll.refresh.timeout.millis=60000

# minimum/maximum wait time client should wait before refreshing
# server provides a random time between these values
poll.refresh.wait.min.millis=6000
poll.refresh.wait.max.millis=10000

sources.properties部分：

# 
# Properties file for EventSource objects to be instantiated.
#
# Place this file in the CLASSPATH (e.g. WEB-INF/classes) or directly under WEB-INF.
#
# $Id: sources.properties,v 1.2 2007/11/10 14:12:16 justb Exp $
#
# Each EventSource is defined as <key>=<classname>
# 1. <key> should be unique within this file but may be any name
# 2. <classname> is the full class name
#
#
# 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=nl.justobjects.pushlet.test.TestEventPullSources$TemperatureEventPullSource
source2=nl.justobjects.pushlet.test.TestEventPullSources$SystemStatusEventPullSource
source3=nl.justobjects.pushlet.test.TestEventPullSources$PushletStatusEventPullSource
source4=nl.justobjects.pushlet.test.TestEventPullSources$AEXStocksEventPullSource
source5=nl.justobjects.pushlet.test.TestEventPullSources$WebPresentationEventPullSource
source6=nl.justobjects.pushlet.test.TestEventPullSources$PingEventPullSource
#source7=com.cisoft.pushlet.PushletUtils$TaskPushlet
#source1=com.cisoft.pushlet.MyPushletSource$MySource1


# TO BE DONE IN NEXT VERSION
# define Push Sources here. These must implement the interface
# nl.justobjects.pushlet.core.EventSource

最后是java代码部分：

package com.cisoft.pushlet;

import java.io.Serializable;

import nl.justobjects.pushlet.core.Event;
import nl.justobjects.pushlet.core.EventPullSource;

public class MyPushletSource implements Serializable{

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;


		 public static class MySource1 extends EventPullSource { 
		
	        @Override 
	        protected long getSleepTime() { 
                 //定时 1秒向客户端 推送一次
	            return 1000;   
		    } 
	        @Override 
	        protected Event pullEvent() { 
	            Event event =Event.createDataEvent("myevent1"); 
	            event.setField("key1","my_value1"); 
	            return event;  
	        } 
		 } 


}

前台页面部分：

<%@ 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="js/pushlet/ajax-pushlet-client.js"></script>   <script type="text/javascript">  
         PL.userId='piero';
         PL._init();    
         PL.joinListen('myevent1');   
         function onData(event) {   
            alert(event.get("key1"));    
         }  </script>  </head><body></body></html>

最后 启动tomcat，在浏览器访问jsp页面就可以看到一个定时为1秒钟推送的结果啦！当然这里是很简单的使用pushlet，离我那个需求还差一点，今日太晚了，明天继续总结！

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