Oracle GlassFish(tm) Server Message Queue
5.0

javax.jms
Interface MessageConsumer

All Known Subinterfaces:
QueueReceiver, TopicSubscriber

public interface MessageConsumer

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.

See Also:
QueueReceiver, TopicSubscriber, Session

Method Summary
 void close()
          Closes the message consumer.
 MessageListener getMessageListener()
          Gets the MessageConsumer's MessageListener.
 java.lang.String getMessageSelector()
          Gets this message consumer's message selector expression.
 Message receive()
          Receives the next message produced for this message consumer.
 Message receive(long timeout)
          Receives the next message that arrives within the specified timeout interval.
 Message receiveNoWait()
          Receives the next message if one is immediately available.
 void setMessageListener(MessageListener listener)
          Sets the MessageConsumer's MessageListener.
 

Method Detail

getMessageSelector

java.lang.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 JMS 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 Java 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 JMS 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 Java EE web or EJB application (though it is not guaranteed that an exception is thrown in this case)
See Also:
setMessageListener(javax.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 Java 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 JMS 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 Java 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 JMS 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 JMS 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 JMS 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 blocks until a receive or message listener in progress has completed. A blocked message consumer receive call returns null when this message consumer is closed.

A MessageListener must not attempt to close its own MessageConsumer as this would lead to deadlock. The JMS provider must detect this and throw a IllegalStateException.

Throws:
IllegalStateException - this method has been called by a MessageListener on its own MessageConsumer
JMSException - if the JMS provider fails to close the consumer due to some internal error.

Oracle GlassFish(tm) Server Message Queue
5.0

Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.