Inherits from KCObject : NSObject
Declared in KMMessageConsumer.h

Overview

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 message consumer 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 message consumer’s messages or have the consumer asynchronously deliver them as they arrive.

For synchronous receipt, 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.

For asynchronous delivery, 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.

Tasks

Instance Methods

close

Closes the message consumer.

- (void)close

Discussion

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 receive call returns nil when this message consumer is closed.

Exceptions

KMJMSException

if the JMS provider fails to close the consumer due to some internal error.

Declared In

KMMessageConsumer.h

messageListener

Gets the message consumer’s MessageListener.

- (id<KMMessageListener>)messageListener

Return Value

the listener for the message consumer, or null if no listener is set

Exceptions

KMJMSException

if the JMS provider fails to get the message listener due to some internal error.

See Also

Declared In

KMMessageConsumer.h

messageSelector

Gets this message consumer’s message selector expression.

- (NSString *)messageSelector

Return Value

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)

Exceptions

KMJMSException

if the JMS provider fails to get the message selector due to some internal error.

Declared In

KMMessageConsumer.h

receive

Receives the next message produced for this message consumer.

- (KMMessage *)receive

Return Value

the next message produced for this message consumer, or null if this message consumer is concurrently closed

Discussion

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.

Exceptions

KMJMSException

if the JMS provider fails to receive the next message due to some internal error.

Declared In

KMMessageConsumer.h

receive:

Receives the next message that arrives within the specified timeout interval.

- (KMMessage *)receive:(long long)timeout

Parameters

timeout

the timeout value (in milliseconds)

Return Value

the next message produced for this message consumer, or null if the timeout expires or this message consumer is concurrently closed

Discussion

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.

Exceptions

KMJMSException

if the JMS provider fails to receive the next message due to some internal error.

Declared In

KMMessageConsumer.h

receiveNoWait

Receives the next message if one is immediately available.

- (KMMessage *)receiveNoWait

Return Value

the next message produced for this message consumer, or null if one is not available

the next message produced for this message consumer, or null if one is not available

Exceptions

KMJMSException

if the JMS provider fails to receive the next message due to some internal error.

Declared In

KMMessageConsumer.h

setMessageListener:

Sets the message consumer’s MessageListener.

- (void)setMessageListener:(id<KMMessageListener>)listener

Parameters

listener

the listener to which the messages are to be delivered

Discussion

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

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

Exceptions

KMJMSException

if the JMS provider fails to set the message listener due to some internal error.

See Also

Declared In

KMMessageConsumer.h