ActiveMQ之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