The so-called three-story development I have mentioned in front of the simple talk about that the code of the entire business is to represent layer / business logic layer / data access layer database, etc., some are fine, clear client Represents layers, business logic access, and data access, and database access, compared to single-layer structures more beneficial to software development, maintenance, deployment, and expansion.
Software layers, in fact, in order to solve problems, easy to control, easy to extend, and easy to allocate resources.
The advantage of the three-layer structure is:
1. By dividing the entire software business into different logical layers, the cost of development and maintenance of application software is reduced, and productivity is improved.
The three-layer structure converts the performance (interface and service) section and the service logic part according to the client layer and the application server, the communication between the client and the application server, the application server, and the database server and the data exchange between the heterogeneous platform. Others can be implemented through middleware or related procedures. When the business logic of the database or application server changes, the client does not need to change, and vice versa, thereby greatly improving the reuse of the system module, shortening the development cycle, reducing maintenance costs.
Just like a classmate of a class, I will buy food by Zhang **, Liu ** prepares the cutlery ... We can easily know what everyone is prepared, it is still a little, very savings Time and physical strength. When a classmate is not coming, it will not make the entire plan cannot be executed.
If we are prepared by a classmate, what do you think? Will not be very messy, he is too busy to maintain it.
2. Converse data access and logic operations into components and enhance the reuse of the code.
The method of collecting some common logic operations is set in the logic layer. When there are multiple functions, you can call the closed method to reduce the repetition code in the application, each need to access the database table. The same method
3. The extensibility of the software (upgrade) is greatly enhanced.
Modularization makes the system easily expanded in both longitudinal and horizontal directions: When the customer needs more functions, the function can be added to the software upgrade, and can also increase the size of the system to enhance the network application of the system. Due to the limitations of the system's homogeneration, the distribution data processing is possible. When upgrading or expanding the original function, it is basically not damaged to the stability of the original structure.
