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。