rabbitmq channel參數詳解【轉】

1、Channel 

1.1 channel.exchangeDeclare()：      

type：有direct、fanout、topic三種
durable：true、false true：伺服器重新開機會保留下來Exchange。警告：僅設定此選項，不代表消息持久化。即不保證重新開機後消息還在。原文：true if we are declaring a durable exchange (the exchange will survive a server restart)
autoDelete:true、false.true:當已經沒有消費者時，伺服器是否可以删除該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：會告訴RabbitMQ不要同時給一個消費者推送多于N個消息，即一旦有N個消息還沒有ack，則該consumer将block掉，直到有消息ack
global：true\false 是否将上面設定應用于channel，簡單點說，就是上面限制是channel級别的還是consumer級别      

備注：據說prefetchSize 和global這兩項，rabbitmq沒有實作，暫且不研究      

/**
     * 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：路由鍵，#比對0個或多個單詞，*比對一個單詞，在topic exchange做消息轉發用

mandatory：true：如果exchange根據自身類型和消息routeKey無法找到一個符合條件的queue，那麼會調用basic.return方法将消息返還給生産者。false：出現上述情形broker會直接将消息扔掉      

immediate：true：如果exchange在将消息route到queue(s)時發現對應的queue上沒有消費者，那麼這條消息不會放入隊列中。當與消息routeKey關聯的所有queue(一個或多個)都沒有消費者時，該消息會通過basic.return方法返還給生産者。
BasicProperties ：需要注意的是BasicProperties.deliveryMode，0:不持久化 1：持久化 這裡指的是消息的持久化，配合channel(durable=true),queue(durable)可以實作，即使伺服器當機，消息仍然保留
簡單來說：mandatory标志告訴伺服器至少将該消息route到一個隊列中，否則将消息返還給生産者；immediate标志告訴伺服器如果該消息關聯的queue上有消費者，則馬上将消息投遞給它，如果所有queue都沒有消費者，直接把消息返還給生産者，不用将消息入隊列等待消費者了。      

/**
     * 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:該消息的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:該消息的index
multiple：是否批量.true:将一次性拒絕所有小于deliveryTag的消息。
requeue：被拒絕的是否重新入隊列      

/**
     * 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;      

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

deliveryTag:該消息的index
requeue：被拒絕的是否重新入隊列

channel.basicNack 與 channel.basicReject 的差別在于basicNack可以拒絕多條消息，而basicReject一次隻能拒絕一條消息      

/**
     * 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;      

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

autoAck：是否自動ack，如果不自動ack，需要使用channel.ack、channel.nack、channel.basicReject 進行消息應答      

/**
     * 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;      

1.7 chanel.exchangeBind()

channel.queueBind(queueName, EXCHANGE_NAME, bindingKey);
用于通過綁定bindingKey将queue到Exchange，之後便可以進行消息接收      

/**
     * 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;      

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

durable：true、false true：在伺服器重新開機時，能夠存活      

exclusive ：是否為目前連接配接的專用隊列，在連接配接斷開後，會自動删除該隊列，生産環境中應該很少用到吧。
autodelete：當沒有任何消費者使用時，自動删除該隊列。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;