flex服务器端信息推送

服务器端信息推送就是是继alax之后新兴web技术。come也可称作反向ajax。成熟的java框架是DWR。

该功能可以实现：使服务器能实时地将更新的信息传送到客户端，而无须客户端发出请求，目前有两种实现方式，长轮询和iframe流。

长轮询长轮询是在打开一条连接以后保持，等待服务器推送来数据再关闭的方式。

iframe流iframe流方式是在页面中插入一个隐藏的iframe，利用其src属性在服务器和客户端之间创建一条长链接，服务器向iframe传输数据（通常是HTML，内有负责插入信息的javascript），来实时更新页面。（对于Iframe流没有接触过，暂时不做探究）

下面是一个基于轮询的实例：

 

1. 从adobe官网下载blazeds.war,这是一个压缩包,里面的包含META-INF和WEB-INF两个文件夹,目录结构如下:其中含META-INF仅包含MANIFEST.MF文件, WEB-INF中包含classes、flex、lib及src四个文件夹，其中flex文件夹中包含四个配置文件，lib中包含java和flex通讯所需要的jar包。

Flex文件夹中包含：

Lib文件夹包含：

2. 创建Java后台的推送服务项目

新建一个DynamicWebProject,如:JavaPushServer

点击Next

点击Next

点击Finish,这时候创建了一个空的动态web项目,使用Tomcat6运行.这时候Eclipse中的见到的项目信息如下:Java Resources中的src为java源代码,Libraries中为java运行所依赖的jar包,如果已经配置好了Tomcat运行环境,则Apache Tomcat v6.0…目录下自动加载了Tomcat的jar包,和JRE System Library目录下的jar包

因为通讯需要blazeds,所以,这时候,可以将blazeds.war解压出来的两个文件夹替换掉刚才创建的web工程中WebContent文件目录下的内容.替换之后可以看到WebContent文件夹下内容变化情况:

以及JavaSources中的Libraries中Web App Libraries中增加了很多jar包,这些就是blazeds.war中所包含的jar包

引入blazeds.war之后,开始写Java代码:

创建名为Tick的java实体类:

package com.eunut.vo;//实体类public class Tick {privateString seqno;publicString getSeqno(){returnseqno;}//字符类型,为测试用仅仅加了一个属性,可以为多个publicvoid setSeqno(String seqno){this.seqno=seqno;}}然后再创建一个名为TickCacheServlet的Servlet举例代码如下:import java.io.IOException;importjavax.servlet.ServletException;importjavax.servlet.http.HttpServlet;importjavax.servlet.http.HttpServletRequest;importjavax.servlet.http.HttpServletResponse;import com.eunut.vo.Tick;importflex.messaging.MessageBroker;importflex.messaging.messages.AsyncMessage;importflex.messaging.util.UUIDUtils;/*** Servlet implementation classTickCacheServlet*/public class TickCacheServletextends HttpServlet {privatestatic final long serialVersionUID = 1L;//线程privatestatic FeedThread thread;/*** @see HttpServlet#HttpServlet()*/public TickCacheServlet() {super();// TODO Auto-generated constructor stub}/*** @see HttpServlet#doGet(HttpServletRequestrequest, HttpServletResponse response)*/Protected   void doGet(HttpServletRequest request, HttpServletResponse response) throwsServletException, IOException {//TODO Auto-generated method stubStringcmd=request.getParameter("cmd");if(cmd.equals("start")){start();}if(cmd.equals("stop")){stop();}}/*** @see HttpServlet#doPost(HttpServletRequestrequest, HttpServletResponse response)*/protectedvoid  doPost(HttpServletRequest request, HttpServletResponse response) throwsServletException, IOException {//TODO Auto-generated method stubsuper.doPost(request,response);}//初始化publicvoid init() throws ServletException{super.init();}publicvoid destroy(){super.destroy();}//启动监听Public    void start(){if(thread==null){thread=newFeedThread();thread.start();}System.out.println("start!!!");}//停止监听Public   void stop(){thread.running=false;thread=null;}//循环发送消息进程Public  static class FeedThread extends Thread{Public   boolean running=true;Public  void run(){//总是无法获取msgBroker,web.xml需要有MessageBrokerServlet的配置信息MessageBrokermsgBroker=MessageBroker.getMessageBroker(null);String clientID=UUIDUtils.createUUID();Int i=0;while(running){Tick  tick=new Tick();tick.setSeqno(String.valueOf(i)); System.out.println(i);AsyncMessage msg=new AsyncMessage();msg.setDestination("tick-data-feed");msg.setHeader(AsyncMessage.SUBTOPIC_HEADER_NAME,"tick");msg.setClientId(clientID);msg.setMessageId(UUIDUtils.createUUID());msg.setTimestamp(System.currentTimeMillis());msg.setBody(tick);msgBroker.routeMessageToService(msg,null);i++;try{Thread.sleep(2000);}catch(InterruptedExceptione){}}}}}

3. 修改Java后台的推送服务项目的配置文件:       

WebContent\WEB-INF\messaging-config.xml<?xml version="1.0"encoding="UTF-8"?><serviceid="message-service" class="flex.messaging.services.MessageService"><adapters><adapter-definitionid="actionscript"class="flex.messaging.services.messaging.adapters.ActionScriptAdapter"default="true" /><!-- <adapter-definitionid="jms"class="flex.messaging.services.messaging.adapters.JMSAdapter"/>--></adapters><default-channels><channelref="my-polling-amf"/></default-channels><!-- 增加配置信息 --><destination id="tick-data-feed"> <properties> <server> <allow-subtopics>true</allow-subtopics> <subtopic-separator>.</subtopic-separator> </server> </properties> <channels> <channel ref="my-polling-amf" /> <channel ref="my-streaming-amf" /> </channels> </destination> </service>以及services-config.xml中补充:<!-- 补充my-streaming-amf通道配置信息 --><channel-definitionid="my-streaming-amf"class="mx.messaging.channels.StreamingAMFChannel"> <endpointurl="http://{server.name}:{server.port}/{context.root}/messagebroker/streamingamf"class="flex.messaging.endpoints.StreamingAMFEndpoint"/> <properties> <idle-timeout-minutes>0</idle-timeout-minutes> <max-streaming-clients>10</max-streaming-clients> <server-to-client-heartbeat-millis>5000</server-to-client-heartbeat-millis> <user-agent-settings> <user-agent match-on="MSIE"kickstart-bytes="2048"max-streaming-connections-per-session="1"/> <user-agentmatch-on="Firefox" kickstart-bytes="2048"max-streaming-connections-per-session="1"/> </user-agent-settings> </properties> </channel-definition> 同时,还要确保web.xml中包含下面的内容:<!-- MessageBroker Servlet-必须的,否则获取不到MessageBrokerServlet,无法发送消息 --><servlet><servlet-name>MessageBrokerServlet</servlet-name><display-name>MessageBrokerServlet</display-name><servlet-class>flex.messaging.MessageBrokerServlet</servlet-class><init-param><param-name>services.configuration.file</param-name><param-value>/WEB-INF/flex/services-config.xml</param-value></init-param><load-on-startup>1</load-on-startup></servlet><servlet-mapping><servlet-name>MessageBrokerServlet</servlet-name><url-pattern>/messagebroker/*</url-pattern></servlet-mapping><!-- 下面的是自动生成的 --><servlet><javaee:description></javaee:description><javaee:display-name>TickCacheServlet</javaee:display-name><servlet-name>TickCacheServlet</servlet-name><servlet-class>TickCacheServlet</servlet-class></servlet><servlet-mapping><servlet-name>TickCacheServlet</servlet-name><url-pattern>/TickCacheServlet</url-pattern></servlet-mapping>

4. 创建Flex客户端应用程序FlexPushClient.mxml:

<?xml version="1.0"encoding="utf-8"?><s:Applicationxmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:s="library://ns.adobe.com/flex/spark" xmlns:mx="library://ns.adobe.com/flex/mx"minWidth="955" minHeight="600"><fx:Declarations><!--将非可视元素（例如服务、值对象）放在此处 --></fx:Declarations><fx:Script><![CDATA[importcom.eunut.Tick;importmx.controls.Alert;importmx.messaging.ChannelSet;importmx.messaging.Consumer;importmx.messaging.channels.StreamingAMFChannel;importmx.messaging.events.ChannelEvent;importmx.messaging.events.MessageEvent;[Bindable] publicvar tick:Tick; publicfunction submsg():void{varconsumer:Consumer=new Consumer();consumer.destination="tick-data-feed";consumer.subtopic="tick";consumer.addEventListener(MessageEvent.MESSAGE,messageHandler);varurl:String ="http://localhost:8080/JavaPushServer/"; varmyStreamingAMF:StreamingAMFChannel = newStreamingAMFChannel(url+"my-streaming-amf",url+"messagebroker/streamingamf"); varchannelSet:ChannelSet = new ChannelSet();channelSet.addChannel(myStreamingAMF);consumer.channelSet= channelSet; // consumer.channelSet = newChannelSet(["my-streaming-amf"]); consumer.subscribe(); //开始接收Alert.show("消费者初始化完毕！"); }privatefunction messageHandler(event:MessageEvent):void { vartick:Tick = event.message.body as Tick; txtTick.text= tick.seqno; } ]]></fx:Script><mx:Panelx="24" y="35" width="362" height="302"layout="absolute" title="Watch Tick"> <mx:Labelx="72" y="43" text="Label"id="txtTick"/> <mx:Buttonx="132" y="41" label="Button"click="submsg()"/> </mx:Panel> </s:Application>还要创建Tick的as类:package com.eunut{importmx.rpc.remoting.RemoteObject;[RemoteClass(alias="com.eunut.vo.Tick")] //用于和java后台类转换alias为java类的命名空间,否则不能转换[Bindable] publicclass Tick{publicfunction Tick(){}publicvar seqno:String; }}

配置此flex的应用程序的服务器为刚才创建好的JavaPushServer

好了,这样就可以了哦,现在就是如果看到推送的效果了,启动方式如下:

首先运行发布到Tomcat上的JavaPushServer,然后,打开客户端网址:http://localhost:8080/JavaPushServer/FlexPushClient.html

这时候显示的界面如下:

此时,点击Button按钮,启动监听程序.

然后,需要启动服务器端的监听:

http://localhost:8080/JavaPushServer/TickCacheServlet?cmd=start

如果一切顺利,则可以看到Label显示的数字从0开始逐个增加.

通过调用:

http://localhost:8080/JavaPushServer/TickCacheServlet?cmd=stop

就关闭服务器端的监听程序

注意:途中可能出现这样那样的问题,绝大部分都是因为配置文件不正确引起的,所以,遇到问题时,一定要仔细查看配置文件中的内容是否正确.

路径问题：比如包名的层次结构是否相同，若不同则需要多处修改。

在这，在对servlet操作时，上述的路径也不是绝对的，参考自己web.xml中的配置进行相应修改