【转】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。