Module jakarta.messaging
Package jakarta.jms

Interface MessageConsumer

  • All Superinterfaces:
    AutoCloseable
    All Known Subinterfaces:
    QueueReceiver, TopicSubscriber
    public interface MessageConsumer
extends AutoCloseable
    A client uses a MessageConsumer object to receive messages from a destination. A MessageConsumer object is created by passing a Destination object to a message-consumer creation method supplied by a session.

    MessageConsumer is the parent interface for all message consumers.

    A MessageConsumer can be created with a message selector. A message selector allows the client to restrict the messages delivered to the message consumer to those that match the selector.

    A client may either synchronously receive a MessageConsumer's messages or have the MessageConsumer asynchronously deliver them as they arrive.

    For synchronous receipt, a client can request the next message from a MessageConsumer using one of its receive methods. There are several variations of receive that allow a client to poll or wait for the next message.

    For asynchronous delivery, a client can register a MessageListener object with a MessageConsumer. As messages arrive at the MessageConsumer, it delivers them by calling the MessageListener's onMessage method.

    It is a client programming error for a MessageListener to throw an exception.

    Since:
    JMS 1.0
    Version:
    Jakarta Messaging 2.0
    See Also:
    QueueReceiver, TopicSubscriber, Session

    • Method Detail

      • getMessageSelector

        String getMessageSelector()
                   throws JMSException
        Gets this message consumer's message selector expression.
        Returns:
        this message consumer's message selector, or null if no message selector exists for the message consumer (that is, if the message selector was not set or was set to null or the empty string)
        Throws:
        JMSException - if the Jakarta Messaging provider fails to get the message selector due to some internal error.

      • getMessageListener

        MessageListener getMessageListener()
                            throws JMSException
        Gets the MessageConsumer's MessageListener.

        This method must not be used in a Jakarta EE web or EJB application. Doing so may cause a JMSException to be thrown though this is not guaranteed.

        Returns:
        the MessageConsumer's MessageListener, or null if one was not set
        Throws:
        JMSException - if the Jakarta Messaging provider fails to get the MessageListener for one of the following reasons:
        • an internal error has occurred or
        • this method has been called in a Jakarta EE web or EJB application (though it is not guaranteed that an exception is thrown in this case)
        See Also:
        setMessageListener(jakarta.jms.MessageListener)

      • setMessageListener

        void setMessageListener​(MessageListener listener)
                 throws JMSException
        Sets the MessageConsumer's MessageListener.

        Setting the the MessageListener to null is the equivalent of unsetting the MessageListener for the MessageConsumer.

        The effect of calling this method while messages are being consumed by an existing listener or the MessageConsumer is being used to consume messages synchronously is undefined.

        This method must not be used in a Jakarta EE web or EJB application. Doing so may cause a JMSException to be thrown though this is not guaranteed.

        Parameters:
        listener - the listener to which the messages are to be delivered
        Throws:
        JMSException - if the Jakarta Messaging provider fails to set the MessageConsumer's MessageListener for one of the following reasons:
        • an internal error has occurred or
        • this method has been called in a Jakarta EE web or EJB application (though it is not guaranteed that an exception is thrown in this case)
        See Also:
        getMessageListener()

      • receive

        Message receive()
         throws JMSException
        Receives the next message produced for this message consumer.

        This call blocks indefinitely until a message is produced or until this message consumer is closed.

        If this receive is done within a transaction, the consumer retains the message until the transaction commits.

        Returns:
        the next message produced for this message consumer, or null if this message consumer is concurrently closed
        Throws:
        JMSException - if the Jakarta Messaging provider fails to receive the next message due to some internal error.

      • receive

        Message receive​(long timeout)
         throws JMSException
        Receives the next message that arrives within the specified timeout interval.

        This call blocks until a message arrives, the timeout expires, or this message consumer is closed. A timeout of zero never expires, and the call blocks indefinitely.

        Parameters:
        timeout - the timeout value (in milliseconds)
        Returns:
        the next message produced for this message consumer, or null if the timeout expires or this message consumer is concurrently closed
        Throws:
        JMSException - if the Jakarta Messaging provider fails to receive the next message due to some internal error.

      • receiveNoWait

        Message receiveNoWait()
               throws JMSException
        Receives the next message if one is immediately available.
        Returns:
        the next message produced for this message consumer, or null if one is not available
        Throws:
        JMSException - if the Jakarta Messaging provider fails to receive the next message due to some internal error.

      • close

        void close()
    throws JMSException
        Closes the message consumer.

        Since a provider may allocate some resources on behalf of a MessageConsumer outside the Java virtual machine, clients should close them when they are not needed. Relying on garbage collection to eventually reclaim these resources may not be timely enough.

        This call will block until a receive call in progress on this consumer has completed. A blocked receive call returns null when this message consumer is closed.

        If this method is called whilst a message listener is in progress in another thread then it will block until the message listener has completed.

        This method may be called from a message listener's onMessage method on its own consumer. After this method returns the onMessage method will be allowed to complete normally.

        This method is the only MessageConsumer method that can be called concurrently.

        Specified by:
        close in interface AutoCloseable
        Throws:
        JMSException - if the Jakarta Messaging provider fails to close the consumer due to some internal error.