深入掌握JMS（四）：实战Queue

    Queue实现的是点到点模型，在下面的例子中，启动2个消费者共同监听一个Queue，然后循环给这个Queue中发送多个消息，我们依然采用ActiveMQ。

import javax.jms.Connection;import javax.jms.DeliveryMode;import javax.jms.JMSException;import javax.jms.Message;import javax.jms.MessageConsumer;import javax.jms.MessageListener;import javax.jms.MessageProducer;import javax.jms.Queue;import javax.jms.Session;import javax.jms.TextMessage;import org.apache.activemq.ActiveMQConnectionFactory;import org.apache.activemq.command.ActiveMQQueue;public class QueueTest { public static void main(String[] args) throws Exception { ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory("vm://localhost"); Connection connection = factory.createConnection(); connection.start(); //创建一个Queue Queue queue = new ActiveMQQueue("testQueue"); //创建一个Session Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE); //注册消费者1 MessageConsumer comsumer1 = session.createConsumer(queue); comsumer1.setMessageListener(new MessageListener(){ public void onMessage(Message m) { try { System.out.println("Consumer1 get " + ((TextMessage)m).getText()); } catch (JMSException e) { e.printStackTrace(); } } }); //注册消费者2 MessageConsumer comsumer2 = session.createConsumer(queue); comsumer2.setMessageListener(new MessageListener(){ public void onMessage(Message m) { try { System.out.println("Consumer2 get " + ((TextMessage)m).getText()); } catch (JMSException e) { e.printStackTrace(); } } }); //创建一个生产者，然后发送多个消息。 MessageProducer producer = session.createProducer(queue); for(int i=0; i<10; i++){ producer.send(session.createTextMessage("Message:" + i)); } }}

  运行这个例子会得到下面的输出结果：

Consumer1 get Message:0Consumer2 get Message:1Consumer1 get Message:2Consumer2 get Message:3Consumer1 get Message:4Consumer2 get Message:5Consumer1 get Message:6Consumer2 get Message:7Consumer1 get Message:8Consumer2 get Message:9 
  可以看出每个消息直被消费了一次，但是如果有多个消费者同时监听一个Queue的话，无法确定一个消息最终会被哪一个消费者消费。