rabbitmq channel参数详解

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。

Exchange.DeclareOk exchangeDeclare(String exchange, String type, boolean durable, boolean autoDelete,
                                       Map<String, Object> arguments) throws IOException;

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

/**
 * 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;

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

 
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 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, BasicProperties props, byte[] body) throws IOException;

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;

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;

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;

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
 * explicit acknowledgement and a server-generated consumerTag.
 * @param queue the name of the queue
 * @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 #basicAck
 * @see #basicConsume(String, boolean, String, boolean, boolean, Map, Consumer)
 */
String basicConsume(String queue, Consumer callback) throws IOException;

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;

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.

/**
 * Actively declare a server-named exclusive, autodelete, non-durable queue.
 * The name of the new queue is held in the "queue" field of the {@link com.rabbitmq.client.AMQP.Queue.DeclareOk} result.
 * @see com.rabbitmq.client.AMQP.Queue.Declare
 * @see com.rabbitmq.client.AMQP.Queue.DeclareOk
 * @return a declaration-confirm method to indicate the queue was successfully declared
 * @throws java.io.IOException if an error is encountered
 */
Queue.DeclareOk queueDeclare() throws IOException;