Service-Oriented Architecture (SOA) -- (5) about MEP (message exchange patterns)

MEP in SOA is similar to JMS in javaee. Of course it should be similar, because it is about message. One is the solution to messages in the system architecture, and the other is the specific solution to messages in the Java platform (strictly speaking, it is not specific, but it only provides interfaces) or, like the above analysis of BPM and jpbm, the former is a special case of the latter, so the latter has many features. As described in the JMS specification, messages are nothing more than requests and responses. There are two basic modes here, which are actually very simple. The first is the request/response, and the second is the request does not respond (one way ). If two one-way messages are delivered, the request/response mode can be similar. However, there is a difference between them. One-way message transmission is not blocked. If a message is sent, the sender does not need to link the message, and the request/response is blocked. As long as the recipient does not respond, the sender thinks that the message is not successfully sent and may resend the message or take other measures to ensure the secure arrival of the message. The advantage of a request/response is that the objects for processing messages remain unchanged. Which is better? You need to choose based on your actual business.

Based on the above two basic MEP, we can develop more complex MEP. Request/callback refers to a one-step Request Response Mode similar to Ajax. After a request is sent, the system does not care about the message on the surface. However, when the response arrives, it takes corresponding measures, that is, "Callback ". Publish/subscribe. It is worthwhile that an RSS-like publisher is responsible for pushing messages to subscribed users, in SOA, messages may be received by a service or a system that combines multiple services.

 

There are still a lot of details in MEP, such as handling error messages, for example, the Protocol needs to be developed between each service module and ESB, and the delay processing for multi-layer protocol MEP.