JSP business Logic Layer

Classic three-tier architecture: Presentation layer, business logic layer, and data access layer

Specific methods of differentiation

1: Data access layer: The main view of your data layer contains no logical processing, in fact, his various functions mainly to complete the operation of the data files. Without having to worry about other operations.

2: Business Logic Layer: mainly responsible for the operation of the data layer. In other words, the operation of some data layers is combined.

3: Presentation layer: The primary request is accepted by the user, and the data is returned, providing the client with access to the application. Presentation Layer

On the outermost (topmost), closest to the user. Used to display data and receive user input data, to provide users with an interactive interface. Business Logic Layer

The business logic layer is undoubtedly the part of the system architecture that embodies the core value. Its focus is mainly on the development of business rules, the implementation of business processes and other business requirements related to the system design, that is, it is related to the domain of the system (domain) logic, and many times, the business logic layer is also called the domain layer. For example, Martin Fowler, in the book Patterns of Enterprise application Architecture, divides the entire architecture into three main layers: the presentation layer, the domain layer, and the data source layer. As a pioneer in domain-driven design, Eric Evans has made a more detailed division of the business Logic layer, subdivided into application and domain layers, and further separates domain logic from domain logic solutions through layering.

The position of the business logic layer in the architecture is critical, it is in the middle of the data access layer and the presentation layer, which plays the role of connecting link in the data exchange. Since the layer is a weakly coupled structure, the dependencies between layers and layers are downward, and the bottom layer is "ignorant" to the upper layer, and changing the upper-level design has no effect on the bottom of its invocation. If you follow the idea of interface-oriented design in a layered design, this downward dependency should also be a weak dependency. Therefore, without changing the definition of the interface, the ideal layered architecture should be a "drawer" architecture which can be extracted and replaceable. Because of this, the design of the business logic layer is especially critical for a scalable architecture, because it plays two different roles. For the data access layer, it is the caller and, for the presentation layer, it is the callee. Dependency and dependent relationships are entangled in the business logic layer, and how to implement the decoupling of dependencies is a task left to the designer in addition to implementing business logic. Data layer

Data Access layer: sometimes referred to as the persistence layer, its function is mainly responsible for database access, access to the database system, binary files, text documents or XML documents.

The simple argument is to implement the select,insert,update,delete of the data table. If you want to add an ORM element, it will include the mapping between the object and the data table, and the persistence of the object entity.

A broad business logic layer