Flex之旅--Flex数据推送

        本文介绍怎样使用Flex数据推送实现前台消息订阅，是在前面Flex+BlazeDS+Spring整合基础上进行的，利用Spring来简化配置。环境准备：

                1.完成Flex+BlazeDS+Spring整合

                2.修改项目根目录下.flexProperties文件中serverContextRoot为项目名，否则后台接收不到前台订阅信息(此处浪费了我很多时间，一定注意)

        修改配置文件

        1.修改WEB-INF/flex/services-config.xml，添加如下代码：

<channel-definition id="my-streaming-amf" class="mx.messaging.channels.StreamingAMFChannel"><endpoint url="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-agent match-on="Firefox" kickstart-bytes="2048" max-streaming-connections-per-session="1"/></user-agent-settings></properties></channel-definition>

        2.修改Spring配置文件applicationContext.xml，把<flex:message-broker/>替换为如下代码：

 <!-- allow-subtopics设为true，允许订阅者订阅指定主题消息 --> <flex:message-destination id="data_push" allow-subtopics="true" subtopic-separator="."/><flex:message-broker><flex:message-service default-channels="my-streaming-amf,my-polling-amf"/></flex:message-broker>  <bean id="messageTemplate" class="org.springframework.flex.messaging.MessageTemplate" />

其中"my-streaming-amf,my-polling-amf"要在services-config.xml中配置，messageTemplate在代码中实现推送功能。

        后台推送数据

        1.添加推送数据Service，代码如下，注意msg设置的各参数，前后台及配置文件都要对应

package demo.flex.service;import javax.annotation.Resource;import org.springframework.flex.messaging.AsyncMessageCreator;import org.springframework.flex.messaging.MessageTemplate;import org.springframework.stereotype.Service;import flex.messaging.messages.AsyncMessage;import flex.messaging.util.UUIDUtils;@Servicepublic class DataPushService {@Resourceprivate MessageTemplate messageTemplate;public void push(String topic, Object data) {messageTemplate.send(new CustomAsyncMessageCreator(topic, data));}class CustomAsyncMessageCreator implements AsyncMessageCreator {private String topic;private Object data;public CustomAsyncMessageCreator(String topic, Object data) {this.topic = topic;this.data = data;}@Overridepublic AsyncMessage createMessage() {AsyncMessage msg = new AsyncMessage();msg.setClientId(UUIDUtils.createUUID());msg.setMessageId(UUIDUtils.createUUID());msg.setTimestamp(System.currentTimeMillis());msg.setDestination("data_push");// 必须和配置文件中message-destination相同msg.setHeader("DSSubtopic", topic);// 设置订阅主题msg.setBody(data);return msg;}}}

        2.添加控制数据开始推送及结束推送Controller，每隔一秒推送当前系统时间

package demo.flex.mvc;import java.text.SimpleDateFormat;import java.util.Date;import javax.annotation.Resource;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.RequestMapping;import demo.flex.service.DataPushService;@Controllerpublic class DataPush {private static FeedThread thread;@Resourceprivate DataPushService dataPushService;@RequestMapping("push")public String push(String cmd) throws Exception {if ("start".equals(cmd)) {start();}else {stop();}return "push";}private void start() {if (thread == null) {thread = new FeedThread();thread.start();}System.out.println("开始数据推送...");}private void stop() {thread.running = false;thread = null;System.out.println("结束数据推送...");}public class FeedThread extends Thread {public boolean running = true;private SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");public void run() {while (running) {String time = sdf.format(new Date());System.out.println(">>>>>>>>>>>" + time);// time为订阅主题dataPushService.push("time", time);try {Thread.sleep(1000);} catch (InterruptedException e) {}}}}}

        3.为使DataPush能够正常运行，修改web.xml及applicationContext.xml配置，添加如下代码：

<!-- mvc mapping--><servlet-mapping><servlet-name>Spring MVC Dispatcher Servlet</servlet-name><url-pattern>/mvc/*</url-pattern></servlet-mapping>

 <mvc:annotation-driven /><bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">  <property name="prefix" value="/WEB-INF/jsp/"/>  <property name="suffix" value=".jsp"/> <property name="viewClass" value="org.springframework.web.servlet.view.JstlView" /></bean> 

        前台订阅功能

        前台FlexDemo.mxml中添加如下代码，订阅主题为time的消息，用于显示后台系统时间

<s:Group horizontalCenter="0"><s:Label text="系统时间："/><s:TextInput id="timeText" text="systime" editable="false" x="80" y="0" width="200"/><s:Button label="显示时间" x="60" y="40" click="showTimeHandler(event)"/><s:Button label="隐藏时间" x="155" y="40" click="hideTimeHandler(event)"/></s:Group>

private var consumer:Consumer;protected function showTimeHandler(event:MouseEvent):void{if (consumer == null) {consumer = new Consumer(); // consumer设置的参数要与后台配置对应consumer.destination = "data_push"; consumer.channelSet = new ChannelSet(["my-streaming-amf","my-polling-amf"]);// 只能收到主题为time的订阅消息consumer.subtopic = "time"; //添加message的监听，当后台有消息发送时，调用messageHandler consumer.addEventListener(MessageEvent.MESSAGE, messageHandler); // 订阅consumer.subscribe();}}protected function hideTimeHandler(event:MouseEvent):void{if (consumer != null) {// 取消订阅consumer.unsubscribe();consumer.removeEventListener(MessageEvent.MESSAGE, messageHandler); consumer = null;timeText.text = "systime"; }}private function messageHandler(event:MessageEvent):void { var time:String = event.message.body as String; timeText.text = time; }

消息订阅也可以采用MultiTopicProducer，能够在单个消息处理程序中同时订阅主题，通过addSubscription(topic)方法订阅主题，removeSubscription(topic)取消订阅。Consumer只能订阅单个主题。

        所有代码已写完，启动项目进行测试！

        1.订阅消息：打开链接http://localhost:8080/FlexDemo/FlexDemo.html，点击显示时间订阅time消息，点击隐藏时间取消订阅

        2.推送消息：打开链接http://localhost:8080/FlexDemo/mvc/push?cmd=start推送消息，http://localhost:8080/FlexDemo/mvc/push?cmd=stop停止推送

        经过测试，my-streaming-amf、my-polling-amf两个通道都可以实现消息推送订阅，但my-streaming-amf发送订阅请求后会一直维护这一个请求直到取消订阅，my-polling-amf会根据配置文件中设定的时间间隔，每过一段时间发送一次订阅请求，获得后台订阅的信息。

        最后附完整代码下载地址：http://download.csdn.net/detail/sjepy/5522399