com.rabbitmq.client

Class QueueingConsumer

java.lang.Object

com.rabbitmq.client.DefaultConsumer

com.rabbitmq.client.QueueingConsumer

All Implemented Interfaces:

Consumer

Deprecated.

public class QueueingConsumer
extends DefaultConsumer

Convenience class: an implementation of Consumer with straightforward blocking semantics. Deprecated in favor of DefaultConsumer (see below for background). Will be removed in next major release. The general pattern for using QueueingConsumer is as follows:

 // Create connection and channel.
 ConnectionFactory factory = new ConnectionFactory();
 Connection conn = factory.newConnection();
 Channel ch1 = conn.createChannel();

 // Declare a queue and bind it to an exchange.
 String queueName = ch1.queueDeclare().getQueue();
 ch1.queueBind(queueName, exchangeName, queueName);

 // Create the QueueingConsumer and have it consume from the queue
 QueueingConsumer consumer = new QueueingConsumer(ch1);
 ch1.basicConsume(queueName, false, consumer);

 // Process deliveries
 while (/* some condition * /) {
     QueueingConsumer.Delivery delivery = consumer.nextDelivery();
     // process delivery
     ch1.basicAck(delivery.getEnvelope().getDeliveryTag(), false);
 }
 

For a more complete example, see LogTail in the test/src/com/rabbitmq/examples directory of the source distribution.

Historical Perspective

QueueingConsumer was introduced to allow applications to overcome a limitation in the way Connection managed threads and consumer dispatching. When QueueingConsumer was introduced, callbacks to Consumers were made on the Connection's thread. This had two main drawbacks. Firstly, the Consumer could stall the processing of all Channels on the Connection. Secondly, if a Consumer made a recursive synchronous call into its Channel the client would deadlock.

QueueingConsumer provided client code with an easy way to obviate this problem by queueing incoming messages and processing them on a separate, application-managed thread.

The threading behaviour of Connection and Channel has been changed so that each Channel uses a distinct thread for dispatching to Consumers. This prevents Consumers on one Channel holding up Consumers on another and it also prevents recursive calls from deadlocking the client. As such, it is now safe to implement Consumer directly or to extend DefaultConsumer and QueueingConsumer is a lot less relevant.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	QueueingConsumer.Delivery Deprecated. Encapsulates an arbitrary message - simple "bean" holder structure.

Constructor Summary

Constructors

Constructor and Description
QueueingConsumer(Channel ch) Deprecated.
QueueingConsumer(Channel ch, BlockingQueue<QueueingConsumer.Delivery> q) Deprecated.

Method Summary

Modifier and Type	Method and Description
void	handleCancel(String consumerTag) Deprecated. No-op implementation of Consumer.handleCancel(String)
void	handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) Deprecated. No-op implementation of Consumer.handleDelivery(java.lang.String, com.rabbitmq.client.Envelope, com.rabbitmq.client.AMQP.BasicProperties, byte[]).
void	handleShutdownSignal(String consumerTag, ShutdownSignalException sig) Deprecated. No-op implementation of Consumer.handleShutdownSignal(java.lang.String, com.rabbitmq.client.ShutdownSignalException).
QueueingConsumer.Delivery	nextDelivery() Deprecated. Main application-side API: wait for the next message delivery and return it.
QueueingConsumer.Delivery	nextDelivery(long timeout) Deprecated. Main application-side API: wait for the next message delivery and return it.

Methods inherited from class com.rabbitmq.client.DefaultConsumer

getChannel, getConsumerTag, handleCancelOk, handleConsumeOk, handleRecoverOk

Methods inherited from class java.lang.Object

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

Constructor Detail

QueueingConsumer

public QueueingConsumer(Channel ch)

Deprecated.

QueueingConsumer

public QueueingConsumer(Channel ch,
                        BlockingQueue<QueueingConsumer.Delivery> q)

Deprecated.

Method Detail

handleShutdownSignal

public void handleShutdownSignal(String consumerTag,
                                 ShutdownSignalException sig)

Deprecated.

Description copied from class: DefaultConsumer

No-op implementation of Consumer.handleShutdownSignal(java.lang.String, com.rabbitmq.client.ShutdownSignalException).

Specified by:

handleShutdownSignal in interface Consumer

Overrides:

handleShutdownSignal in class DefaultConsumer

Parameters:

consumerTag - the consumer tag associated with the consumer

sig - a ShutdownSignalException indicating the reason for the shut down

handleCancel

public void handleCancel(String consumerTag)
                  throws IOException

Deprecated.

Description copied from class: DefaultConsumer

No-op implementation of Consumer.handleCancel(String)

Specified by:

handleCancel in interface Consumer

Overrides:

handleCancel in class DefaultConsumer

Parameters:

consumerTag - the defined consumer tag (client- or server-generated)

Throws:

IOException

handleDelivery

public void handleDelivery(String consumerTag,
                           Envelope envelope,
                           AMQP.BasicProperties properties,
                           byte[] body)
                    throws IOException

Deprecated.

Description copied from class: DefaultConsumer

No-op implementation of Consumer.handleDelivery(java.lang.String, com.rabbitmq.client.Envelope, com.rabbitmq.client.AMQP.BasicProperties, byte[]).

Specified by:

handleDelivery in interface Consumer

Overrides:

handleDelivery in class DefaultConsumer

Parameters:

consumerTag - the consumer tag associated with the consumer

envelope - packaging data for the message

properties - content header data for the message

body - the message body (opaque, client-specific byte array)

Throws:

IOException - if the consumer encounters an I/O error while processing the message

See Also:

Envelope

nextDelivery

public QueueingConsumer.Delivery nextDelivery()
                                       throws InterruptedException,
                                              ShutdownSignalException,
                                              ConsumerCancelledException

Deprecated.

Main application-side API: wait for the next message delivery and return it.

Returns:

the next message

Throws:

InterruptedException - if an interrupt is received while waiting

ShutdownSignalException - if the connection is shut down while waiting

ConsumerCancelledException - if this consumer is cancelled while waiting

nextDelivery

public QueueingConsumer.Delivery nextDelivery(long timeout)
                                       throws InterruptedException,
                                              ShutdownSignalException,
                                              ConsumerCancelledException

Deprecated.

Main application-side API: wait for the next message delivery and return it.

Parameters:

timeout - timeout in millisecond

Returns:

the next message or null if timed out

Throws:

InterruptedException - if an interrupt is received while waiting

ShutdownSignalException - if the connection is shut down while waiting

ConsumerCancelledException - if this consumer is cancelled while waiting