知行合一，止于至善
千里之行，始于足下；合抱之木，生于毫末；九层之台，起于累土在spring中使用JMS实现请求/响应模式
demo下载：testjms-request-reply.zip
1、JMS的实现原理
当发起请求时，调用session.createTemporaryQueue()创建一个临时的Queue,调用requestMessage.setJMSReplyTo(responseQueue)将临时Queue和requestMessage关联，这个动作已经被jmsTemplate.sendAndReceive()方法封装了，调用该方法就会返回responseMessage.当应答端收到requestMessage，调用session.createProducer()创建一个messageProducer,调用session.createTextMessage()创建一个message，使用messageProducer.send(requestMsg.getJMSReplyTo(), replyMsg),通过请求中的ReplyTo通道将响应返回给请求端。
2、CorrelationID头设置
如果在请求端你想知道某个响应是和哪个请求关联的。那么我们可以给Message对象添加CorrelationID头，使用jmsTemplate.sendAndReceive()方法的大致代码如下（参考：cn.javacoder.testjms_send.App）：
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Message replyMsg = jmsTemplate.sendAndReceive("test.queue", new MessageCreator() { public Message createMessage(Session session) throws JMSException { ObjectMessage objMsg = session.createObjectMessage(user); String correlationID = UUID.randomUUID().toString(); System.out.println("correlationID:" + correlationID); objMsg.setJMSCorrelationID(correlationID); return objMsg; } }); |
3、响应端的实现
jmsTemplate 没有提供类似receiveAndReply()的方法，所以需要我们自己编码来实现。大致的代码如下(参考：cn.javacoder.testjms_receive.Reply)：
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connection = connectionFactory.createConnection(); connection.start(); session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE); producer = session.createProducer(null); consumer = session.createConsumer(destination); Message msg = consumer.receive(); ObjectMessage objMsg = (ObjectMessage)msg; User user = (User)objMsg.getObject(); System.out.println("receive user:"+ user.getUsername()); TextMessage replyMsg = session.createTextMessage(); replyMsg.setJMSCorrelationID(msg.getJMSCorrelationID()); replyMsg.setText("reply message"); producer.send(msg.getJMSReplyTo(), replyMsg); |
4、参考文档：
1)http://activemq.apache.org/how-should-i-implement-request-response-with-jms.html
2)《ActiveMQ in Action》
Posted in: spring practise | Tags: JMS, spring
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