Three-tier architecture service, dao, controller layer

**My understanding:** asked the pig, the following is the logic of a two-way binding

The controller layer receives the front-end input information and gives a response (whether the front-end and back-end are connected), and then the controller layer passes the information parameters to the service for processing;

Service encapsulates some services and can call the api of the dao layer. The service layer also has many interfaces and implementation classes, and the implementation class calling methods can operate the dao layer;

The dao layer can add, delete, modify, and query a single table or multiple tables.

The dao layer also returns the results of the addition and modification checks to the service layer

The service layer then passes the result to the controller layer

The controller layer then passes the information to the front end

This last cycle is a two-way binding.

But for some businesses, there is no need to implement two-way binding:

For example, if a delete operation is sent from the front end, there is no need to send back the data, just delete it directly.

Some big guys explain these layers 1[Here is picture 001]https://blog.csdn.net/weixin_44471490/article/details/121462038Some big guys explain these layers 2 [here is picture 002]https://blog.csdn.net/qq_22771739/article/details/82344336

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