ActiveMQ的消息确认问题

http://riddickbryant.iteye.com/blog/441890

【发送端】

session = connection.createSession(Boolean.FALSE,  Session.AUTO_ACKNOWLEDGE);

producer.setDeliveryMode(DeliveryMode.PERSISTENT);

 import javax.jms.*;
 import org.apache.activemq.ActiveMQConnection;
 import org.apache.activemq.ActiveMQConnectionFactory;
 /**
  *
  * @author LIN NP
  */
 public class JmsSender{

   private ConnectionFactory connectionFactory = null;
   private Connection connection = null;
   private Session session = null;
   private Destination destination = null;
   private MessageProducer producer = null;

   private static final int SEND_NUMBER = 1;

   public void init()
   {
     // 构造ConnectionFactory实例对象，此处采用ActiveMq的实现jar
     connectionFactory = new ActiveMQConnectionFactory(
         ActiveMQConnection.DEFAULT_USER,
         ActiveMQConnection.DEFAULT_PASSWORD,"tcp://localhost:61616");    // ActiveMQ默认使用的TCP连接端口是61616

     try{
       // 构造从工厂得到连接对象
       connection = connectionFactory.createConnection();
       connection.start();
       // 获取操作连接
       session = connection.createSession(Boolean.FALSE,  Session.AUTO_ACKNOWLEDGE);

       //第一种方式：Queue

 //            destination = session.createQueue("xkey");        // "xkey"可以取其他的。
 //            producer = session.createProducer(destination); // 得到消息生成者【发送者】

       //第二种方式：Topic
        Topic topic = session.createTopic("xkey.Topic");
        producer = session.createProducer(topic);

       // 持久化
       producer.setDeliveryMode(DeliveryMode.PERSISTENT);

       // 构造消息，此处写死，项目就是参数，或者方法获取
       sendMessage(session,producer);

       //session.commit();
     }
     catch(Exception e)
     {
       e.printStackTrace();
     }
     finally
     {
       try
       {
         connection.close();
       }
       catch (JMSException e)
       {
         // TODO Auto-generated catch block
         e.printStackTrace();
       }
     }
   }

   private void sendMessage(Session session,MessageProducer producer) throws JMSException
   {
     for (int i = 1; i <= SEND_NUMBER; i ++)
     {
       TextMessage message = session.createTextMessage("发送消息" + i);  

       System.out.println("发送消息" + i);  

    // 发送消息
       producer.send(message);

     }
   }
   /**
    * @param args
    */
   public static void main(String[] args)
   {
     // TODO Auto-generated method stub
     JmsSender jms = new JmsSender();
     jms.init();
   }
 }

【接收端】

connection = connectionFactory.createConnection();
connection.setClientID("bbb");
connection.start();

session = connection.createSession(Boolean.FALSE,  Session.AUTO_ACKNOWLEDGE);

consumer = session.createDurableSubscriber(topic,"bbb"); //持久订阅

 import javax.jms.*;
 import org.apache.activemq.ActiveMQConnection;
 import org.apache.activemq.ActiveMQConnectionFactory;
 /**
  *
  * @author LIN NP
  */
 public class JmsReceiver
 {
   private ConnectionFactory connectionFactory = null;
   private Connection connection = null;
   private Session session = null;
   private MessageConsumer consumer = null;
   private Destination destination = null;
   public void init()
   {
     connectionFactory = new ActiveMQConnectionFactory(
         ActiveMQConnection.DEFAULT_USER,
         ActiveMQConnection.DEFAULT_PASSWORD,"tcp://localhost:61616"); // ActiveMQ默认使用的TCP连接端口是61616
     try
     {
       // 构造从工厂得到连接对象
       connection = connectionFactory.createConnection();
       connection.setClientID("bbb");
       connection.start();
       // 获取操作连接
       session = connection.createSession(Boolean.FALSE,  Session.AUTO_ACKNOWLEDGE);
       /**
       * 第一种方式：Queue
       */
 //            destination = session.createQueue("xkey");
 //            consumer = session.createConsumer(destination);
       /**
        * 第二种方式：Topic
        */

       Topic topic = session.createTopic("xkey.Topic");
       //consumer = session.createConsumer(topic);
       consumer = session.createDurableSubscriber(topic,"bbb"); //持久订阅

       /**
         *
         */
       while (true)
       {
         //设置接收者接收消息的时间，为了便于测试，这里设定为500s
         TextMessage message = (TextMessage) consumer.receive(500);
         if (null != message)
         {
           System.out.println("Receiver: " + message.getText());
         }
         else
         {
           break;
         }
       }
     }
     catch(Exception e)
     {
       e.printStackTrace();
     }
     finally
     {
       try
       {
         connection.close();
       }
       catch (JMSException e)
       {
         // TODO Auto-generated catch block
         e.printStackTrace();
       }
     }
   }
   /**
    * @param args
    */
   public static void main(String[] args)
   {
     // TODO Auto-generated method stub
     JmsReceiver jms = new JmsReceiver();
     jms.init();
   }
 }

 //创建JMS连接和会话
 ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory(url);
 connection = factory.createConnection();
 connection.setClientID(Constant.JMS_CLIENT_ID);
 session = connection.createSession(true, Session.AUTO_ACKNOWLEDGE);
 // 创建消息发送主题和发送者
 Topic jmsSendTopic = session.createTopic(sendTopic);
 sendTopicProducer = session.createProducer(jmsSendTopic);
 sendTopicProducer.setDeliveryMode(DeliveryMode.PERSISTENT);
 sendTopicProducer.setTimeToLive(Message.DEFAULT_TIME_TO_LIVE);
 // 创建消息接收主题和接收者
 Topic jmsReceiveTopic = session.createTopic(receiveTopic);
 receiveTopicConsumer = session.createDurableSubscriber(jmsReceiveTopic,Constant.JMS_SUBSCRIBE_NAME);
 receiveTopicConsumer.setMessageListener(this);
 connection.start();  

解答：问题原因在于这段代码在接收到JMS消息时不会向ActiveMQ服务器确认消息的接收，故而ActiveMQ服务器一直认为该消息没有成功发送给接收者，因而每次接收者重启之后就会收到ActiveMQ服务器发送过来的消息。在这里要解释一下session的创建。

session = connection.createSession(true,Session.Auto_ACKNOWLEDGE);

当createSession第一个参数为true时，表示创建的session被标记为transactional的，确认消息就通过确认和校正来自动地处理，第二个参数应该是没用的。

当createSession的第一个参数为false时，表示创建的session没有标记为transactional，此时有三种用于消息确认的选项：
**AUTO_ACKNOWLEDGE session将自动地确认收到的一则消息;
**CLIENT_ACKNOWLEDGE 客户端程序将确认收到的一则消息，调用这则消息的确认方法;
**DUPS_OK_ACKNOWLEDGE 这个选项命令session“懒散的”确认消息传递，可以想到，这将导致消息提供者传递的一些复制消息可能出错。

JMS有两种消息传递方式。标记为NON_PERSISTENT的消息最多传递一次，而标记为PERSISTENT的消息将使用暂存后再转发的机理投递。如果一个JMS服务离线，那么持久性消息不会丢失，但是得等到这个服务恢复联机的时候才会被传递。所以默认的消息传递方式是非持久性的，虽然使用非持久性消息可能降低内存和需要的存储器，但这种传递方式只有当你不需要接收所有消息时才使用。
因此正确的代码只需改动一处就行了，即将true改为false

 //创建JMS连接和会话
 ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory(url);
 connection = factory.createConnection();
 connection.setClientID(Constant.JMS_CLIENT_ID);
 session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
 // 创建消息发送主题和发送者
 Topic jmsSendTopic = session.createTopic(sendTopic);
 sendTopicProducer = session.createProducer(jmsSendTopic);
 sendTopicProducer.setDeliveryMode(DeliveryMode.PERSISTENT);
 sendTopicProducer.setTimeToLive(Message.DEFAULT_TIME_TO_LIVE);
 // 创建消息接收主题和接收者
 Topic jmsReceiveTopic = session.createTopic(receiveTopic);
 receiveTopicConsumer = session.createDurableSubscriber(jmsReceiveTopic,Constant.JMS_SUBSCRIBE_NAME);
 receiveTopicConsumer.setMessageListener(this);
 connection.start();