JMS学习(七)

    在下面的例子中，分别发送一个Persistent和nonpersistent的消息，然后关闭退出JMS。

import javax.jms.Connection;
import javax.jms.DeliveryMode;
import javax.jms.MessageProducer;
import javax.jms.Queue;
import javax.jms.Session;
import org.apache.activemq.ActiveMQConnectionFactory;
import org.apache.activemq.command.ActiveMQQueue;

public class DeliveryModeSendTest {

    public static void main(String[] args) throws Exception {
        ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory("vm://localhost");
  
        Connection connection = factory.createConnection();
        connection.start();
      
        Queue queue = new ActiveMQQueue("testQueue");
        Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
              
        MessageProducer producer = session.createProducer(queue);
        producer.setDeliveryMode(DeliveryMode.PERSISTENT);
        producer.send(session.createTextMessage("A persistent Message"));
      
        producer.setDeliveryMode(DeliveryMode.NON_PERSISTENT);
        producer.send(session.createTextMessage("A non persistent Message"));
      
        System.out.println("Send messages sucessfully!");
    }
}

    运行上面的程序，当输出“Send messages sucessfully!”时，说明两个消息都已经发送成功，然后我们结束它，来停止JMS Provider。

    接下来我们重新启动JMS Provicer，然后添加一个消费者：

import javax.jms.Connection;
import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.MessageConsumer;
import javax.jms.MessageListener;
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 DeliveryModeReceiveTest {

    public static void main(String[] args) throws Exception {
        ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory("vm://localhost");
  
        Connection connection = factory.createConnection();
        connection.start();
      
        Queue queue = new ActiveMQQueue("testQueue");
        Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
      
        MessageConsumer comsumer = session.createConsumer(queue);
        comsumer.setMessageListener(new MessageListener(){
            public void onMessage(Message m) {
                try {
                    System.out.println("Consumer get " + ((TextMessage)m).getText());
                } catch (JMSException e) {
                    e.printStackTrace();
                }
            }
        });
    }
}

运行上面的程序，可以得到下面的输出结果：

Consumer get A persistent Message

可以看出消息消费者只接收到一个消息，它是一个Persistent的消息。而刚才发送的non persistent消息已经丢失了。

另外, 如果发送一个non persistent消息, 而刚好这个时候没有消费者在监听, 这个消息也会丢失.