javax.jms
Interface MessageConsumer

All Known Subinterfaces:

QueueReceiver, TopicSubscriber

public interface MessageConsumer

A client uses a message consumer to receive messages from a Destination. It is created by passing a Destination to a create message consumer method supplied by a Session.

The parent interface for all message consumers.

A message consumer can be created with a message selector. This 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 message consumer's messages or have the consumer asynchronously deliver them as they arrive.

A client can request the next message from a message consumer using one of its receive methods. There are several variations of receive that allow a client to poll or wait for the next message.

A client can register a MessageListener object with a message consumer. As messages arrive at the message consumer, it delivers them by calling the MessageListener's onMessage method.

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

Version:

1.0 - 13 March 1998

Author:

Mark Hapner, Rich Burridge

See Also:

QueueReceiver, TopicSubscriber, Session

Method Summary

void	close() Since a provider may allocate some resources on behalf of a MessageConsumer outside the JVM, clients should close them when they are not needed.
MessageListener	getMessageListener() Get the message consumer's MessageListener.
java.lang.String	getMessageSelector() Get this message consumer's message selector expression.
Message	receive() Receive the next message produced for this message consumer.
Message	receive(long timeout) Receive the next message that arrives within the specified timeout interval.
Message	receiveNoWait() Receive the next message if one is immediately available.
void	setMessageListener(MessageListener listener) Set the message consumer's MessageListener.

Method Detail

getMessageSelector

public java.lang.String getMessageSelector()
                                    throws JMSException

Get this message consumer's message selector expression.

Returns:

this message consumer's message selector

Throws:

JMSException - if JMS fails to get message selector due to some JMS error

getMessageListener

public MessageListener getMessageListener()
                                   throws JMSException

Get the message consumer's MessageListener.

Returns:

the listener for the message consumer, or null if there isn't one set.

Throws:

JMSException - if JMS fails to get message listener due to some JMS error

See Also:

setMessageListener(javax.jms.MessageListener)

setMessageListener

public void setMessageListener(MessageListener listener)
                        throws JMSException

Set the message consumer's MessageListener.

Setting the message listener to null is the equivalent of unsetting the message listener for the message consumer.

Calling the setMessageListener method of MessageConsumer while messages are being consumed by an existing listener or the consumer is being used to synchronously consume messages is undefined.

Parameters:

messageListener - the messages are delivered to this listener

Throws:

JMSException - if JMS fails to set message listener due to some JMS error

See Also:

getMessageListener()

receive

public Message receive()
                throws JMSException

Receive 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 message remains on the consumer 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 JMS fails to receive the next message due to some error.

receive

public Message receive(long timeout)
                throws JMSException

Receive 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 return null if timeout expires or message consumer concurrently closed.

Throws:

JMSException - if JMS fails to receive the next message due to some error.

receiveNoWait

public Message receiveNoWait()
                      throws JMSException

Receive 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 JMS fails to receive the next message due to some error.

close

public void close()
           throws JMSException

Since a provider may allocate some resources on behalf of a MessageConsumer outside the JVM, 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.

Throws:

JMSException - if JMS fails to close the consumer due to some error.