JMS之Queue分析

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();
      
        //建立一個Queue
        Queue queue = new ActiveMQQueue("testQueue");
        //建立一個Session
        Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
      
        //註冊消費者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();
                }
            }
        });
      
        //註冊消費者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();
                }
            }
           
        });
      
        //建立一個生產者，而後發送多個消息。
        MessageProducer producer = session.createProducer(queue);
        for(int i=0; i<10; i++){
            producer.send(session.createTextMessage("Message:" + i));
        }
    }
}

運行這個例子會獲得下面的輸出結果：

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
  
  能夠看出每一個消息只被消費了一次，可是若是有多個消費者同時監聽一個Queue的話，沒法肯定一個消息最終會被哪個消費者消費。