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.