1 message in = 2 messages out

Question

Hi,
          I have problems with my JMS queue. If I send 1 message to the queue it
          will give me 2 messages to pick out from the queue. Could it be that
          I'm not acknowledging my messages correctly? I'm really lost.
          Some code to help you understand the problem:
          This is how I put the message in the Q.
          // Look up administred objects
          InitialContext initContext = new InitialContext();
          QueueConnectionFactory factory = (QueueConnectionFactory)
          initContext.lookup(CONNECTION_FACTORY);
          Queue queue = (Queue) initContext.lookup(QUEUE);
          initContext.close();
          // Create JMS objects
          QueueConnection connection = factory.createQueueConnection();
          QueueSession session = connection.createQueueSession(false,
          Session.AUTO_ACKNOWLEDGE);
          QueueSender sender = session.createSender(queue);
          connection.start();
          Message message = session.createMessage();
          ...some code left out...
          // Put the message in the queue
          sender.send(message);
          message.acknowledge();
          session.close();
          connection.close();
          This is how I receive the message from the Q. And this is where I
          fail.
          public void init(){
          try{
          // Look up administred objects
          InitialContext initContext = new InitialContext();
          QueueConnectionFactory factory = (QueueConnectionFactory)
          initContext.lookup(CONNECTION_FACTORY);
          m_queue = (Queue) initContext.lookup(QUEUE);
          initContext.close();
          // Create JMS objects
          m_connection = factory.createQueueConnection();
          m_session = m_connection.createQueueSession(false,
          Session.AUTO_ACKNOWLEDGE);
          m_receiver = m_session.createReceiver(m_queue);
          m_receiver.setMessageListener(this);
          m_connection.start();
          //this.setDaemon(true);
          this.start();
          catch(Exception e){
          public void onMessage(Message message){
          try{
          // Get the properties from the message
          Properties properties = getProperties(message);
          // Create a new MoSms
          MoSms mosm = new MoSms(properties);
          // Send message
          m_session.close();
          m_connection.close();
          SmsMoWB.handleMessage(mosm);
          catch(Exception e){
          public void run(){
          try{
          while(true){
          Message message = m_receiver.receive();
          this.onMessage(message);
          catch (JMSException e) {
          catch (Throwable e) {
          So what am I doing wrong, acknowledging the message sto late, picking
          them out of the Q wrong or what?
          regards,
          Jörgen
          

Answer 1

Looking at the "init" method:
          m_connection = factory.createQueueConnection();
          m_session = m_connection.createQueueSession(false,
          Session.AUTO_ACKNOWLEDGE);
          m_receiver = m_session.createReceiver(m_queue);
          m_receiver.setMessageListener(this);
          m_connection.start();
          When you call "setMessageListener", this tells JMS to automatically call
          "this.onMessage" every time a message appears on "m_queue".
          But then you do this:
          this.start();
          which makes me think that your class extends java.lang.Thread, and inside
          "run" you do this:
          while(true){
          Message message = m_receiver.receive();
          this.onMessage(message);
          Which does the same thing.
          Assuming that "m_receiver" is the same object in both places, then your code
          is "breaking the rules". That is, you're not supposed to use a Session
          object in more than one thread at a time, which is what you're doing, and
          the JMS spec says that what happens in this case is "undefined".
          I bet that if you either call "setMessageListener" or start your thread,
          you'll only get one copy of each message. But doing both is definitely
          wrong, and that may explain why you're seeing what you're seeing.
          greg
          "Jörgen" <[email protected]> wrote in message
          news:[email protected]...
          > Hi,
          > I have problems with my JMS queue. If I send 1 message to the queue it
          > will give me 2 messages to pick out from the queue. Could it be that
          > I'm not acknowledging my messages correctly? I'm really lost.
          >
          > Some code to help you understand the problem:
          >
          > This is how I put the message in the Q.
          >
          > // Look up administred objects
          > InitialContext initContext = new InitialContext();
          > QueueConnectionFactory factory = (QueueConnectionFactory)
          > initContext.lookup(CONNECTION_FACTORY);
          > Queue queue = (Queue) initContext.lookup(QUEUE);
          > initContext.close();
          >
          > // Create JMS objects
          > QueueConnection connection = factory.createQueueConnection();
          > QueueSession session = connection.createQueueSession(false,
          > Session.AUTO_ACKNOWLEDGE);
          > QueueSender sender = session.createSender(queue);
          > connection.start();
          >
          > Message message = session.createMessage();
          >
          > ...some code left out...
          >
          > // Put the message in the queue
          > sender.send(message);
          > message.acknowledge();
          > session.close();
          > connection.close();
          >
          >
          >
          > This is how I receive the message from the Q. And this is where I
          > fail.
          >
          > public void init(){
          > try{
          > // Look up administred objects
          > InitialContext initContext = new InitialContext();
          > QueueConnectionFactory factory = (QueueConnectionFactory)
          > initContext.lookup(CONNECTION_FACTORY);
          > m_queue = (Queue) initContext.lookup(QUEUE);
          > initContext.close();
          >
          > // Create JMS objects
          > m_connection = factory.createQueueConnection();
          > m_session = m_connection.createQueueSession(false,
          > Session.AUTO_ACKNOWLEDGE);
          > m_receiver = m_session.createReceiver(m_queue);
          > m_receiver.setMessageListener(this);
          > m_connection.start();
          >
          > //this.setDaemon(true);
          > this.start();
          > }
          > catch(Exception e){
          > }
          > }
          >
          > public void onMessage(Message message){
          > try{
          > // Get the properties from the message
          > Properties properties = getProperties(message);
          >
          > // Create a new MoSms
          > MoSms mosm = new MoSms(properties);
          >
          > // Send message
          > m_session.close();
          > m_connection.close();
          > SmsMoWB.handleMessage(mosm);
          > }
          > catch(Exception e){
          > }
          > }
          >
          > public void run(){
          > try{
          > while(true){
          > Message message = m_receiver.receive();
          > this.onMessage(message);
          > }
          > }
          > catch (JMSException e) {
          > }
          > catch (Throwable e) {
          > }
          > }
          >
          >
          > So what am I doing wrong, acknowledging the message sto late, picking
          > them out of the Q wrong or what?
          >
          > regards,
          > Jörgen