com.amazon.sqs.javamessaging

Class SQSMessageConsumer

java.lang.Object

com.amazon.sqs.javamessaging.SQSMessageConsumer

public class SQSMessageConsumer
extends java.lang.Object

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.

This message consumer does not support message selectors

A client may either synchronously receive a message consumer's messages or have the consumer asynchronously deliver them as they arrive via registering a MessageListener object.

The message consumer creates a background thread to prefetch the messages to improve the receive turn-around times.

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	closed
static int	PREFETCH_EXECUTOR_GRACEFUL_SHUTDOWN_TIME

Method Summary

Methods

Modifier and Type	Method and Description
void	close() Closes the message consumer.
MessageListener	getMessageListener() Gets the message consumer's MessageListener.
java.lang.String	getMessageSelector() This method is not supported.
Queue	getQueue() Gets the queue destination associated with this queue receiver, where the messages are delivered from.
Message	receive() This call blocks indefinitely until a message is produced or until this message consumer is closed.
Message	receive(long timeout) This call blocks until a message arrives, the timeout expires, or this message consumer is closed.
Message	receiveNoWait() Receives the next message if one is immediately available.
void	setMessageListener(MessageListener listener) Sets the message consumer's MessageListener.
protected void	startPrefetch() This starts the prefetching
protected void	stopPrefetch() This stops the prefetching

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

PREFETCH_EXECUTOR_GRACEFUL_SHUTDOWN_TIME

public static final int PREFETCH_EXECUTOR_GRACEFUL_SHUTDOWN_TIME

See Also:

Constant Field Values

closed

protected volatile boolean closed

Method Detail

getQueue

public Queue getQueue()
               throws JMSException

Gets the queue destination associated with this queue receiver, where the messages are delivered from.

Returns:

a queue destination

Throws:

JMSException

getMessageListener

public MessageListener getMessageListener()
                                   throws JMSException

Gets the message consumer's MessageListener.

Returns:

a message listener

Throws:

JMSException

setMessageListener

public void setMessageListener(MessageListener listener)
                        throws JMSException

Sets the message consumer's MessageListener.

Parameters:

listener - a message listener to use for asynchronous message delivery

Throws:

JMSException - If the message consumer is closed

receive

public Message receive()
                throws JMSException

This call blocks indefinitely until a message is produced or until this message consumer is closed. When ConnectionState is stopped receive is paused.

Returns:

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

Throws:

JMSException - On internal error

receive

public Message receive(long timeout)
                throws JMSException

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 closed

Throws:

JMSException - On internal error

receiveNoWait

public 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 no message is available

Throws:

JMSException - On internal error

close

public void close()
           throws JMSException

Closes the message consumer.

This will not return until receives and/or message listeners in progress have completed. A blocked message consumer receive call returns null when this consumer is closed.

Since consumer prefetch threads use SQS long-poll feature with 20 seconds timeout, closing each consumer prefetch thread can take up to 20 seconds, which in-turn will impact the time on consumer close.

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, and the callback scheduler thread will be closing the message consumer.

Throws:

JMSException - On internal error.

getMessageSelector

public java.lang.String getMessageSelector()
                                    throws JMSException

This method is not supported.

Throws:

JMSException

stopPrefetch

protected void stopPrefetch()

This stops the prefetching

startPrefetch

protected void startPrefetch()

This starts the prefetching