- channel.exchangeDeclare()：

type：有direct、fanout、topic三種
durable：true、false true：伺服器重啟會保留下來Exchange。警告：僅設定此選項，不代表訊息持久化。即不保證重啟後訊息還在。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，伺服器是否可以刪除該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;
 

• chanel.basicQos()
  prefetchSize：0
  prefetchCount：會告訴RabbitMQ不要同時給一個消費者推送多於N個訊息，即一旦有N個訊息還沒有ack，則該consumer將block掉，直到有訊息ack
  global：true\false 是否將上面設定應用於channel，簡單點說，就是上面限制是channel級別的還是consumer級別
  備註：據說prefetchSize 和global這兩項，rabbitmq沒有實現，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;
 

• channel.basicPublish()
  routingKey：路由鍵，#匹配0個或多個單詞，*匹配一個單詞，在topic exchange做訊息轉發用

mandatory：true：如果exchange根據自身型別和訊息routeKey無法找到一個符合條件的queue，那麼會呼叫basic.return方法將訊息返還給生產者。false：出現上述情形broker會直接將訊息扔掉
immediate：true：如果exchange在將訊息route到queue(s)時發現對應的queue上沒有消費者，那麼這條訊息不會放入佇列中。當與訊息routeKey關聯的所有queue(一個或多個)都沒有消費者時，該訊息會通過basic.return方法返還給生產者。
BasicProperties ：需要注意的是BasicProperties.deliveryMode，0:不持久化 1：持久化 這裡指的是訊息的持久化，配合channel(durable=true),queue(durable)可以實現，即使伺服器宕機，訊息仍然保留
簡單來說：mandatory標誌告訴伺服器至少將該訊息route到一個佇列中，否則將訊息返還給生產者；immediate標誌告訴伺服器如果該訊息關聯的queue上有消費者，則馬上將訊息投遞給它，如果所有queue都沒有消費者，直接把訊息返還給生產者，不用將訊息入佇列等待消費者了。

/**
     * 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;

• channel.basicAck()
  deliveryTag:該訊息的index
  multiple：是否批量.true:將一次性ack所有小於deliveryTag的訊息。

    /**
     * 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;

• channel.basicNack(delivery.getEnvelope().getDeliveryTag(), false,
  true);
  deliveryTag:該訊息的index
  multiple：是否批量.true:將一次性拒絕所有小於deliveryTag的訊息。
  requeue：被拒絕的是否重新入佇列

    /**
     * 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;

• 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 進行訊息應答

    /**
     * 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;

• chanel.exchangeBind()

channel.queueBind(queueName, EXCHANGE_NAME, bindingKey);
用於通過繫結bindingKey將queue到Exchange，之後便可以進行訊息接收

/**
     * 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;

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

durable：true、false true：在伺服器重啟時，能夠存活
exclusive ：是否為當前連線的專用佇列，在連線斷開後，會自動刪除該佇列，生產環境中應該很少用到吧。
autodelete：當沒有任何消費者使用時，自動刪除該佇列。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;