In back-end development, how to distinguish the responsibilities of the service layer and the dao layer?

Back-end development layered architecture: Detailed explanation of responsibilities of Service layer and DAO layer

In back-end development, hierarchical architectures (such as including Controller, Service, and DAO layers) are common design patterns. The Controller handles front-end interaction, the Service is responsible for business logic, and the DAO is responsible for data access. However, especially after the introduction of the Manager layer, the responsibility boundaries between the Service layer and the DAO layer are often blurred. This article will explore how to clearly distinguish these two levels.

Definition between business logic and non-business logic

First of all, it is crucial to clarify the difference between business logic and non-business logic. Business logic directly relates to business needs (such as user registration and order processing), which users can perceive; non-business logic is irrelevant to business needs, but is essential for system operation (such as database table structure design, password salt).

The following are the following examples listed in the article:

1. Table structure and table association relationship: belong to non-business logic. usermanager.delete() and departmentmanager.delete() can handle association table deletion at the same time, which is the responsibility of the DAO layer or the Manager layer. Even without the Manager layer, the DAO layer can handle cross-table operations. As long as these operations are not related to business logic, there is no need to call the DAO layer multiple times at the Service layer. In the example code, usermanager and departmentmanager are more suitable for classification in the Manager layer.

2. Password salt: non-business logic. The salting operation should be processed in the DAO layer or the Manager layer to ensure the password is secure without exposure to the Service layer. In the example code, it is appropriate to integrate password salt logic directly into UserDao .

3. DAO layer method naming and setting: DAO layer method naming (for example, get_super_user ) is as long as it has nothing to do with business logic. If it is related to business, it should be handled at the Service layer.

4. HTTP request encapsulation: Some dependencies can be encapsulated in the DAO layer instead of the Service layer to reduce the complexity of the Service layer.

Data filtering in Django/Flask

In the Django/Flask framework, data filtering can be implemented using Django filter or similar mechanisms. In the Python three-layer architecture, if you want to implement similar functions, you can pass in request parameters at the DAO layer and pass them layer by layer. In the absence of automatic injection frameworks such as Spring, parameters need to be passed manually. In Java development, Spring Data JPA provides similar functions.

The correspondence between data entities and hierarchy

Data entity corresponds to database table objects. Controller, Service and DAO layers do not correspond one by one. The DAO layer may correspond to multiple Service layer methods, while the Service layer method may call multiple DAO layer methods. The key is to design a hierarchical structure according to business needs.

In summary, a hierarchical architecture is designed to divide systems by responsibility. The DAO layer is only responsible for data access and does not include business logic; the Service layer handles business logic. It is crucial to flexibly adjust the hierarchical structure to meet actual development needs.

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