深入掌握JMS(七):DeliveryMode例子

    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.

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