ActiveMQ之deliveryMode

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.