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。