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//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
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//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// [email protected].
package com.rabbitmq.client.amqp;
import java.util.Map;
/**
* API to consume messages from a RabbitMQ queue.
*
* Instances are configured and created with a {@link ConsumerBuilder}.
*
* @see Connection#consumerBuilder()
* @see ConsumerBuilder
*/
public interface Consumer extends AutoCloseable, Resource {
/** Pause the consumer to stop receiving messages. */
void pause();
/**
* Return the number of unsettled messages.
*
* @return unsettled message count
*/
long unsettledMessageCount();
/** Request to receive messages again. */
void unpause();
/** Close the consumer with its resources. */
@Override
void close();
/** Contract to process a message. */
@FunctionalInterface
interface MessageHandler {
/**
* Process a message
*
* @param context message context
* @param message message
*/
void handle(Context context, Message message);
}
/** Context for message processing. */
interface Context {
/**
* Accept the message (AMQP 1.0 accepted outcome).
*
*
This means the message has been processed and the broker can delete it.
*/
void accept();
/**
* Discard the message (AMQP 1.0 rejected outcome).
*
*
This means the message cannot be processed because it is invalid, the broker can drop it
* or dead-letter it if it is configured.
*/
void discard();
/**
* Discard the message with annotations to combine with the existing message annotations.
*
*
This means the message cannot be processed because it is invalid, the broker can drop it
* or dead-letter it if it is configured.
*
*
Application-specific annotation keys must start with the x-opt- prefix.
* Annotation keys the broker understands start with x-, but not with x-opt-
* .
*
*
This maps to the AMQP 1.0
* modified{delivery-failed = true, undeliverable-here = true} outcome.
*
*
Only quorum queues support the modification of message annotations with the
* modified outcome.
*
* @param annotations message annotations to combine with existing ones
* @see AMQP
* 1.0 modified outcome
* @see Modified Outcome Support
* in RabbitMQ
*/
void discard(Map annotations);
/**
* Requeue the message (AMQP 1.0 released outcome).
*
* This means the message has not been processed and the broker can requeue it and deliver it
* to the same or a different consumer.
*/
void requeue();
/**
* Requeue the message with annotations to combine with the existing message annotations.
*
*
This means the message has not been processed and the broker can requeue it and deliver it
* to the same or a different consumer.
*
*
Application-specific annotation keys must start with the x-opt- prefix.
* Annotation keys the broker understands start with x-, but not with x-opt-
* .
*
*
This maps to the AMQP 1.0
* modified{delivery-failed = false, undeliverable-here = false} outcome.
*
*
Only quorum queues support the modification of message annotations with the
* modified outcome.
*
* @param annotations message annotations to combine with existing ones
* @see AMQP
* 1.0 modified outcome
* @see Modified Outcome Support
* in RabbitMQ
*/
void requeue(Map annotations);
}
}