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:0
            Consumer2 get Message:1
            Consumer1 get Message:2
            Consumer2 get Message:3
            Consumer1 get Message:4
            Consumer2 get Message:5
            Consumer1 get Message:6
            Consumer2 get Message:7
            Consumer1 get Message:8
            Consumer2 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。