RabbitMQ channel 参数详解

1.Channel

1.1 channel.exchangeDeclare()：

type：有direct、fanout、topic三种
durable：true、false true：服务器重启会保留下来Exchange。警告：仅设置此选项，不代表消息持久化。即不保证重启后消息还在。原文：true if we are declaring a durable exchange (the exchange will survive a server restart)
autoDelete:true、false.true:当已经没有消费者时，服务器是否可以删除该Exchange。原文1：true if the server should delete the exchange when it is no longer in use。

  /**
      * Declare an exchange.
      * @see com.rabbitmq.client.AMQP.Exchange.Declare
      * @see com.rabbitmq.client.AMQP.Exchange.DeclareOk
      * @param exchange the name of the exchange
      * @param type the exchange type
      * @param durable true if we are declaring a durable exchange (the exchange will survive a server restart)
      * @param autoDelete true if the server should delete the exchange when it is no longer in use
      * @param arguments other properties (construction arguments) for the exchange
      * @return a declaration-confirm method to indicate the exchange was successfully declared
      * @throws java.io.IOException if an error is encountered
      */
     Exchange.DeclareOk exchangeDeclare(String exchange, String type, boolean durable, boolean autoDelete,
                                        Map<String, Object> arguments) throws IOException;

1.2 chanel.basicQos()

prefetchSize：0
prefetchCount：会告诉RabbitMQ不要同时给一个消费者推送多于N个消息，即一旦有N个消息还没有ack，则该consumer将block掉，直到有消息ack
global：true\false 是否将上面设置应用于channel，简单点说，就是上面限制是channel级别的还是consumer级别
备注：据说prefetchSize 和global这两项，rabbitmq没有实现，暂且不研究

    /**
      * Request specific "quality of service" settings.
      *
      * These settings impose limits on the amount of data the server
      * will deliver to consumers before requiring acknowledgements.
      * Thus they provide a means of consumer-initiated flow control.
      * @see com.rabbitmq.client.AMQP.Basic.Qos
      * @param prefetchSize maximum amount of content (measured in
      * octets) that the server will deliver, 0 if unlimited
      * @param prefetchCount maximum number of messages that the server
      * will deliver, 0 if unlimited
      * @param global true if the settings should be applied to the
      * entire channel rather than each consumer
      * @throws java.io.IOException if an error is encountered
      */
     void basicQos(int prefetchSize, int prefetchCount, boolean global) throws IOException;

1.3 channel.basicPublish()

routingKey：路由键，#匹配0个或多个单词，*匹配一个单词，在topic exchange做消息转发用

mandatory：true：如果exchange根据自身类型和消息routeKey无法找到一个符合条件的queue，那么会调用basic.return方法将消息返还给生产者。false：出现上述情形broker会直接将消息扔掉
immediate：true：如果exchange在将消息route到queue(s)时发现对应的queue上没有消费者，那么这条消息不会放入队列中。当与消息routeKey关联的所有queue(一个或多个)都没有消费者时，该消息会通过basic.return方法返还给生产者。
BasicProperties ：需要注意的是BasicProperties.deliveryMode，0:不持久化 1：持久化 这里指的是消息的持久化，配合channel(durable=true),queue(durable)可以实现，即使服务器宕机，消息仍然保留
简单来说：mandatory标志告诉服务器至少将该消息route到一个队列中，否则将消息返还给生产者；immediate标志告诉服务器如果该消息关联的queue上有消费者，则马上将消息投递给它，如果所有queue都没有消费者，直接把消息返还给生产者，不用将消息入队列等待消费者了。

   /**
      * Publish a message.
      *
      * Publishing to a non-existent exchange will result in a channel-level
      * protocol exception, which closes the channel.
      *
      * Invocations of <code>Channel#basicPublish</code> will eventually block if a
      * <a href="http://www.rabbitmq.com/alarms.html">resource-driven alarm</a> is in effect.
      *
      * @see com.rabbitmq.client.AMQP.Basic.Publish
      * @see <a href="http://www.rabbitmq.com/alarms.html">Resource-driven alarms</a>.
      * @param exchange the exchange to publish the message to
      * @param routingKey the routing key
      * @param mandatory true if the 'mandatory' flag is to be set
      * @param immediate true if the 'immediate' flag is to be
      * set. Note that the RabbitMQ server does not support this flag.
      * @param props other properties for the message - routing headers etc
      * @param body the message body
      * @throws java.io.IOException if an error is encountered
      */
     void basicPublish(String exchange, String routingKey, boolean mandatory, boolean immediate, BasicProperties props, byte[] body)
             throws IOException;

1.4 channel.basicAck();

deliveryTag:该消息的index
multiple：是否批量.true:将一次性ack所有小于deliveryTag的消息。

     /**
      * Acknowledge one or several received
      * messages. Supply the deliveryTag from the {@link com.rabbitmq.client.AMQP.Basic.GetOk}
      * or {@link com.rabbitmq.client.AMQP.Basic.Deliver} method
      * containing the received message being acknowledged.
      * @see com.rabbitmq.client.AMQP.Basic.Ack
      * @param deliveryTag the tag from the received {@link com.rabbitmq.client.AMQP.Basic.GetOk} or {@link com.rabbitmq.client.AMQP.Basic.Deliver}
      * @param multiple true to acknowledge all messages up to and
      * including the supplied delivery tag; false to acknowledge just
      * the supplied delivery tag.
      * @throws java.io.IOException if an error is encountered
      */
     void basicAck(long deliveryTag, boolean multiple) throws IOException;

1.5 channel.basicNack(delivery.getEnvelope().getDeliveryTag(), false, true);

deliveryTag:该消息的index
multiple：是否批量.true:将一次性拒绝所有小于deliveryTag的消息。
requeue：被拒绝的是否重新入队列

     /**
      * Reject one or several received messages.
      *
      * Supply the <code>deliveryTag</code> from the {@link com.rabbitmq.client.AMQP.Basic.GetOk}
      * or {@link com.rabbitmq.client.AMQP.Basic.GetOk} method containing the message to be rejected.
      * @see com.rabbitmq.client.AMQP.Basic.Nack
      * @param deliveryTag the tag from the received {@link com.rabbitmq.client.AMQP.Basic.GetOk} or {@link com.rabbitmq.client.AMQP.Basic.Deliver}
      * @param multiple true to reject all messages up to and including
      * the supplied delivery tag; false to reject just the supplied
      * delivery tag.
      * @param requeue true if the rejected message(s) should be requeued rather
      * than discarded/dead-lettered
      * @throws java.io.IOException if an error is encountered
      */
     void basicNack(long deliveryTag, boolean multiple, boolean requeue)
             throws IOException;

1.6 channel.basicReject(delivery.getEnvelope().getDeliveryTag(), false);

deliveryTag:该消息的index
requeue：被拒绝的是否重新入队列

channel.basicNack 与 channel.basicReject 的区别在于basicNack可以拒绝多条消息，而basicReject一次只能拒绝一条消息

  /**
      * Reject a message. Supply the deliveryTag from the {@link com.rabbitmq.client.AMQP.Basic.GetOk}
      * or {@link com.rabbitmq.client.AMQP.Basic.Deliver} method
      * containing the received message being rejected.
      * @see com.rabbitmq.client.AMQP.Basic.Reject
      * @param deliveryTag the tag from the received {@link com.rabbitmq.client.AMQP.Basic.GetOk} or {@link com.rabbitmq.client.AMQP.Basic.Deliver}
      * @param requeue true if the rejected message should be requeued rather than discarded/dead-lettered
      * @throws java.io.IOException if an error is encountered
      */
     void basicReject(long deliveryTag, boolean requeue) throws IOException;

1.7 channel.basicConsume(QUEUE_NAME, true, consumer);

autoAck：是否自动ack，如果不自动ack，需要使用channel.ack、channel.nack、channel.basicReject 进行消息应答

     /**
      * Start a non-nolocal, non-exclusive consumer, with
      * a server-generated consumerTag.
      * @param queue the name of the queue
      * @param autoAck true if the server should consider messages
      * acknowledged once delivered; false if the server should expect
      * explicit acknowledgements
      * @param callback an interface to the consumer object
      * @return the consumerTag generated by the server
      * @throws java.io.IOException if an error is encountered
      * @see com.rabbitmq.client.AMQP.Basic.Consume
      * @see com.rabbitmq.client.AMQP.Basic.ConsumeOk
      * @see #basicConsume(String, boolean, String, boolean, boolean, Map, Consumer)
      */
     String basicConsume(String queue, boolean autoAck, Consumer callback) throws IOException;

1.8 chanel.exchangeBind()

channel.queueBind(queueName, EXCHANGE_NAME, bindingKey);
用于通过绑定bindingKey将queue到Exchange，之后便可以进行消息接收

     /**
      * Bind an exchange to an exchange, with no extra arguments.
      * @see com.rabbitmq.client.AMQP.Exchange.Bind
      * @see com.rabbitmq.client.AMQP.Exchange.BindOk
      * @param destination the name of the exchange to which messages flow across the binding
      * @param source the name of the exchange from which messages flow across the binding
      * @param routingKey the routine key to use for the binding
      * @return a binding-confirm method if the binding was successfully created
      * @throws java.io.IOException if an error is encountered
      */
     Exchange.BindOk exchangeBind(String destination, String source, String routingKey) throws IOException;

1.9 channel.queueDeclare(QUEUE_NAME, false, false, false, null);

durable：true、false true：在服务器重启时，能够存活
exclusive ：是否为当前连接的专用队列，在连接断开后，会自动删除该队列，生产环境中应该很少用到吧。
autodelete：当没有任何消费者使用时，自动删除该队列。this means that the queue will be deleted when there are no more processes consuming messages from it.

  /**
      * Declare a queue
      * @see com.rabbitmq.client.AMQP.Queue.Declare
      * @see com.rabbitmq.client.AMQP.Queue.DeclareOk
      * @param queue the name of the queue
      * @param durable true if we are declaring a durable queue (the queue will survive a server restart)
      * @param exclusive true if we are declaring an exclusive queue (restricted to this connection)
      * @param autoDelete true if we are declaring an autodelete queue (server will delete it when no longer in use)
      * @param arguments other properties (construction arguments) for the queue
      * @return a declaration-confirm method to indicate the queue was successfully declared
      * @throws java.io.IOException if an error is encountered
      */
     Queue.DeclareOk queueDeclare(String queue, boolean durable, boolean exclusive, boolean autoDelete,
                                  Map<String, Object> arguments) throws IOException;

参考：http://blog.csdn.net/jiao_fuyou/article/details/21594947