释放双眼，带上耳机，听听看~！
6. RPC
But what if we need to run a function on a remote computer and wait for the result? Well, that’s a different story. This pattern is commonly known as Remote Procedure Call or RPC.
大概意思是说，上面几种模式都是生产者将消息发送到Rabbitmq，然后就不管了，也不管是否有消费者进行了消费，也不管消费的结果是怎样的。上面几种场景已经可以满足大多数需求。但是有一种场景是生产者必须知道消费结果才能进行后续操作，
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图示
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Our RPC will work like this:
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For an RPC request, the Client sends a message with two properties: replyTo, which is set to a anonymous exclusive queue created just for the request, and correlationId, which is set to a unique value for every request.
- The request is sent to an rpc_queue queue.
- The RPC worker (aka: server) is waiting for requests on that queue. When a request appears, it does the job and sends a message with the result back to the Client, using the queue from the replyTo field.
- The client waits for data on the reply queue. When a message appears, it checks the correlationId property. If it matches the value from the request it returns the response to the application.
源代码: 基于xml配置的SpringMvc项目https://github.com/FutaoSmile/SpringMvcStudyBaseXML
