深入掌握JMS（十）：JMSCorrelationID与Selector

前面讲过JMSCorrelationID主要是用来关联多个Message，例如需要回复一个消息的时候，通常把回复的消息的
           JMSCorrelationID设置为原来消息的ID。在下面这个例子中，创建了三个消息生产者A，B，C和三个消息消费者A，B，C。生产者A给消费者A发送一个消息，同时需要消费者A给它回复一个消息。B、C与A类似。
               简图如下：
                  生产者A-----发送----〉消费者A-----回复------〉生产者A
                   生产者B-----发送----〉消费者B-----回复------〉生产者B
                   生产者C-----发送----〉消费者C-----回复------〉生产者C
               需要注意的是，所有的发送和回复都使用同一个Queue，通过Selector区分。

           import javax.jms.*;
           import org.apache.activemq.ActiveMQConnectionFactory;
           import org.apache.activemq.command.ActiveMQQueue;

           public class JMSCorrelationIDTest {
               private Queue queue;
               private Session session;
               public JMSCorrelationIDTest() throws JMSException{
                   ActiveMQConnectionFactory factory = new
           ActiveMQConnectionFactory("vm://localhost");
                   Connection connection = factory.createConnection();
                   connection.start();
                   queue = new ActiveMQQueue("testQueue");
                   session = connection.createSession(false,
           Session.AUTO_ACKNOWLEDGE);
                   setupConsumer("ConsumerA");
                   setupConsumer("ConsumerB");
                   setupConsumer("ConsumerC");
                   setupProducer("ProducerA", "ConsumerA");
                   setupProducer("ProducerB", "ConsumerB");
                   setupProducer("ProducerC", "ConsumerC");
               }
               private void setupConsumer(final String name) throws
           JMSException {
                   //创建一个消费者，它只接受属于它自己的消息
                   MessageConsumer consumer = session.createConsumer(queue,
           "receiver='" + name + "'");
                   consumer.setMessageListener(new MessageListener(){
                       public void onMessage(Message m) {
                           try {
                               MessageProducer producer =
           session.createProducer(queue);
                               System.out.println(name + " get:" +
           ((TextMessage)m).getText());
                               //回复一个消息
                               Message replyMessage =
           session.createTextMessage("Reply from " + name);
                               //设置JMSCorrelationID为刚才收到的消息的ID
           replyMessage.setJMSCorrelationID(m.getJMSMessageID());
                               producer.send(replyMessage);
                           } catch (JMSException e) { }
                       }
                   });
               }

               private void setupProducer(final String name, String
           consumerName) throws JMSException {
                   MessageProducer producer = session.createProducer(queue);
                   producer.setDeliveryMode(DeliveryMode.NON_PERSISTENT);
                   //创建一个消息，并设置一个属性receiver，为消费者的名字。
                   Message message = session.createTextMessage("Message from "
           + name);
                   message.setStringProperty("receiver", consumerName);
                   producer.send(message);
                   //等待回复的消息
                   MessageConsumer replyConsumer =
           session.createConsumer(queue, "JMSCorrelationID='" +
           message.getJMSMessageID() + "'");
                   replyConsumer.setMessageListener(new MessageListener(){
                       public void onMessage(Message m) {
                           try {
                               System.out.println(name + " get reply:" +
           ((TextMessage)m).getText());
                           } catch (JMSException e) { }
                       }
                   });
               }
               public static void main(String[] args) throws Exception {
                   new JMSCorrelationIDTest ();
               }
           }

           运行结果为：
           ConsumerA get:Message from ProducerA
           ProducerA get reply:Reply from ConsumerA
           ConsumerB get:Message from ProducerB
           ProducerB get reply:Reply from ConsumerB
           ConsumerC get:Message from ProducerC
           ProducerC get reply:Reply from ConsumerC