AMQP-801-2: Introduce ConsumerDecorator

JIRA: https://jira.spring.io/browse/AMQP-801

To properly assign the queue to the `ConsumeOkEvent`, we need perform
such a logic in the `Consumer.handleConsumeOk()`.

* Introduce `BlockingQueueConsumer.ConsumerDecorator` to be created on
each `channel.basicConsume()` for wrapping the target `InternalConsumer`
per queue
* Add getters to the `ConsumeOkEvent` for better interoperability
* Assert assigned queue names for the `ConsumeOkEvent`s in the
`SimpleMessageListenerContainerIntegration2Tests`

**Cherry-pick to 1.7.x**

* Add `ConsumerDecorator.consumerTag` property
* Add `ConsumerDecorator.toString()`
* Add JavaDocs for the `ConsumeOkEvent`

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/listener/BlockingQueueConsumer.java

@@ -62,6 +62,7 @@
 import com.rabbitmq.client.AMQP;
 import com.rabbitmq.client.AlreadyClosedException;
 import com.rabbitmq.client.Channel;
+import com.rabbitmq.client.Consumer;
 import com.rabbitmq.client.DefaultConsumer;
 import com.rabbitmq.client.Envelope;
 import com.rabbitmq.client.Recoverable;
@@ -237,10 +238,11 @@ public BlockingQueueConsumer(ConnectionFactory connectionFactory,
 	 * @param queues The queues.
 	 */
 	public BlockingQueueConsumer(ConnectionFactory connectionFactory,
-             MessagePropertiesConverter messagePropertiesConverter,
-             ActiveObjectCounter<BlockingQueueConsumer> activeObjectCounter, AcknowledgeMode acknowledgeMode,
-             boolean transactional, int prefetchCount, boolean defaultRequeueRejected,
-             Map<String, Object> consumerArgs, boolean exclusive, String... queues) {
+			MessagePropertiesConverter messagePropertiesConverter,
+			ActiveObjectCounter<BlockingQueueConsumer> activeObjectCounter, AcknowledgeMode acknowledgeMode,
+			boolean transactional, int prefetchCount, boolean defaultRequeueRejected,
+			Map<String, Object> consumerArgs, boolean exclusive, String... queues) {
+
 		this(connectionFactory, messagePropertiesConverter, activeObjectCounter, acknowledgeMode, transactional,
 				prefetchCount, defaultRequeueRejected, consumerArgs, false, exclusive, queues);
 	}
@@ -483,7 +485,9 @@ private Message handle(Delivery delivery) throws InterruptedException {
 	 * @throws ShutdownSignalException if the connection is shut down while waiting
 	 */
 	public Message nextMessage() throws InterruptedException, ShutdownSignalException {
-		logger.trace("Retrieving delivery for " + this);
+		if (logger.isTraceEnabled()) {
+			logger.trace("Retrieving delivery for " + this);
+		}
 		return handle(this.queue.take());
 	}
 
@@ -673,8 +677,10 @@ private void addRecoveryListener() {
 
 	private void consumeFromQueue(String queue) throws IOException {
 		String consumerTag = this.channel.basicConsume(queue, this.acknowledgeMode.isAutoAck(),
-				(this.tagStrategy != null ? this.tagStrategy.createConsumerTag(queue) : ""), this.noLocal, this.exclusive,
-				this.consumerArgs, this.consumer);
+				(this.tagStrategy != null ? this.tagStrategy.createConsumerTag(queue) : ""), this.noLocal,
+				this.exclusive, this.consumerArgs,
+				new ConsumerDecorator(queue, this.consumer, this.applicationEventPublisher));
+
 		if (consumerTag != null) {
 			this.consumerTags.put(consumerTag, queue);
 			if (logger.isDebugEnabled()) {
@@ -817,7 +823,7 @@ public boolean commitIfNecessary(boolean locallyTransacted) throws IOException {
 		 */
 		boolean isLocallyTransacted = locallyTransacted
 				|| (this.transactional
-						&& TransactionSynchronizationManager.getResource(this.connectionFactory) == null);
+				&& TransactionSynchronizationManager.getResource(this.connectionFactory) == null);
 		try {
 
 			boolean ackRequired = !this.acknowledgeMode.isAutoAck() && !this.acknowledgeMode.isManual();
@@ -884,11 +890,6 @@ public void handleConsumeOk(String consumerTag) {
 			if (logger.isDebugEnabled()) {
 				logger.debug("ConsumeOK: " + BlockingQueueConsumer.this);
 			}
-			if (BlockingQueueConsumer.this.applicationEventPublisher != null) {
-				String queueName = BlockingQueueConsumer.this.consumerTags.get(consumerTag);
-				BlockingQueueConsumer.this.applicationEventPublisher
-						.publishEvent(new ConsumeOkEvent(this, queueName, consumerTag));
-			}
 		}
 
 		@Override
@@ -962,6 +963,68 @@ public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProp
 
 	}
 
+	private static final class ConsumerDecorator implements Consumer {
+
+		private final String queue;
+
+		private final Consumer delegate;
+
+		private final ApplicationEventPublisher applicationEventPublisher;
+
+		private String consumerTag;
+
+		ConsumerDecorator(String queue, Consumer delegate, ApplicationEventPublisher applicationEventPublisher) {
+			this.queue = queue;
+			this.delegate = delegate;
+			this.applicationEventPublisher = applicationEventPublisher;
+		}
+
+
+		@Override
+		public void handleConsumeOk(String consumerTag) {
+			this.consumerTag = consumerTag;
+			this.delegate.handleConsumeOk(consumerTag);
+			if (this.applicationEventPublisher != null) {
+				this.applicationEventPublisher.publishEvent(new ConsumeOkEvent(this.delegate, this.queue, consumerTag));
+			}
+		}
+
+		@Override
+		public void handleShutdownSignal(String consumerTag, ShutdownSignalException sig) {
+			this.delegate.handleShutdownSignal(consumerTag, sig);
+		}
+
+		@Override
+		public void handleCancel(String consumerTag) throws IOException {
+			this.delegate.handleCancel(consumerTag);
+		}
+
+		@Override
+		public void handleCancelOk(String consumerTag) {
+			this.delegate.handleCancelOk(consumerTag);
+		}
+
+		@Override
+		public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties,
+				byte[] body) throws IOException {
+
+			this.delegate.handleDelivery(consumerTag, envelope, properties, body);
+		}
+
+		@Override
+		public void handleRecoverOk(String consumerTag) {
+			this.delegate.handleRecoverOk(consumerTag);
+		}
+
+		@Override
+		public String toString() {
+			return "ConsumerDecorator{" + "queue='" + this.queue + '\'' +
+					", consumerTag='" + this.consumerTag + '\'' +
+					'}';
+		}
+
+	}
+
 	@SuppressWarnings("serial")
 	private static final class DeclarationException extends AmqpException {
 

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/listener/ConsumeOkEvent.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017 the original author or authors.
+ * Copyright 2017-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,7 +19,12 @@
 import org.springframework.amqp.event.AmqpEvent;
 
 /**
+ * An {@link AmqpEvent} emitted by the listener container
+ * when consumer is subscribed to the queue.
+ *
  * @author Gary Russell
+ * @author Artem Bilan
+ *
  * @since 1.7.5
  *
  */
@@ -30,12 +35,37 @@ public class ConsumeOkEvent extends AmqpEvent {
 
 	private final String consumerTag;
 
+	/**
+	 * Instantiate a {@link ConsumeOkEvent} based on the provided
+	 * consumer, queue and consumer tag.
+	 * @param source the consumer subscribed to the queue
+	 * @param queue the queue to consume
+	 * @param consumerTag the tag indicate a consumer subscription
+	 */
 	public ConsumeOkEvent(Object source, String queue, String consumerTag) {
 		super(source);
 		this.queue = queue;
 		this.consumerTag = consumerTag;
 	}
 
+	/**
+	 * Obtain the queue name a consumer has been subscribed.
+	 * @return the queue name a consumer subscribed.
+	 * @since 1.7.7
+	 */
+	public String getQueue() {
+		return this.queue;
+	}
+
+	/**
+	 * Obtain the consumer tag assigned to the consumer.
+	 * @return the consumer tag for subscription.
+	 * @since 1.7.7
+	 */
+	public String getConsumerTag() {
+		return this.consumerTag;
+	}
+
 	@Override
 	public String toString() {
 		return "ConsumeOkEvent [queue=" + this.queue + ", consumerTag=" + this.consumerTag

spring-rabbit/src/test/java/org/springframework/amqp/rabbit/listener/SimpleMessageListenerContainerIntegration2Tests.java

@@ -20,6 +20,7 @@
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.instanceOf;
+import static org.hamcrest.Matchers.isOneOf;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNull;
@@ -90,6 +91,7 @@
  * @author Gunnar Hillert
  * @author Gary Russell
  * @author Artem Bilan
+ *
  * @since 1.3
  *
  */
@@ -283,7 +285,11 @@ public void publishEvent(ApplicationEvent event) {
 		assertThat(events.size(), equalTo(8));
 		assertThat(events.get(0), instanceOf(AsyncConsumerStartedEvent.class));
 		assertThat(events.get(1), instanceOf(ConsumeOkEvent.class));
+		ConsumeOkEvent consumeOkEvent = (ConsumeOkEvent) events.get(1);
+		assertThat(consumeOkEvent.getQueue(), isOneOf(this.queue.getName(), this.queue1.getName()));
 		assertThat(events.get(2), instanceOf(ConsumeOkEvent.class));
+		consumeOkEvent = (ConsumeOkEvent) events.get(2);
+		assertThat(consumeOkEvent.getQueue(), isOneOf(this.queue.getName(), this.queue1.getName()));
 		assertSame(events.get(3), eventRef.get());
 		assertThat(events.get(4), instanceOf(AsyncConsumerRestartedEvent.class));
 		assertThat(events.get(5), instanceOf(ConsumeOkEvent.class));