What are the three layer design work for the three layer structure design?

The three-layer architecture is as follows: the three-layer architecture is to conform to the idea of "high cohesion, low coupling", and the presentation layer (UI); Business Logic Layer (BLL); Data Access Layer (DAL) is a three-tier architecture.

The entity classes of different object models generally correspond to different tables in the database, and the attributes of the entity classes are consistent with the field names of the data closure database tables.

The purpose of the three-layer architecture is to distinguish the levels for "high cohesion and low coupling". The division of labor of developers is clearer, and they will focus more on the analysis, design and development of the core business logic of the application system, which will speed up the progress of the project, improve the development efficiency, and be conducive to the update and maintenance of the project.

The three-tier architecture mainly refers to the presentation layer UI, data access layer DAL, and business logic layer BLL in business application planning, and the core task of its layering is the implementation of "high cohesion and low coupling". In the whole software architecture, the hierarchical structure is a common and common software architecture framework, and it also has a very important position and significance.

Generally, the three layers are the data access layer, the business logic layer, and the presentation layer. There is also a solid layer.

The entity layer mainly corresponds to the tables in the database, and generally one table corresponds to one entity class. The entity class is mainly used as a data carrier in the project.

The data access layer is a layer that interacts with the database for data, and the common practice is to write a dbhelper class, which provides database connection, database command operations, and returns data, which is a general class, and then there are many entity database access classes in it. The dbhelper class is called to operate with the database.

The business logic layer mainly calls the data access layer, obtains basic data from the data access layer, and then performs different logical operations according to the requirements, and processes the data to the presentation layer. This layer class is mainly a logical operation class of the entity class.

The presentation layer is a web** or winform form. An interface used to display data and interact with users. It depends on the demand.

That's the basic picture.

Three-tier architecture?

The three-layer architecture is generally the data access layer, the business logic layer, and the presentation layer, which is the interface layer, which is used to display the interface.

To put it simply, the data access layer is to add or delete everything that needs to be checked in the database to be placed in this layer, and the business logic layer is to put everything that needs to be judged on events and methods in this layer, that is, the judgment logic, the interface layer (representation layer), and the ** displayed by the interface is placed in this layer, and the role of this is 1Easy to modify, especially the data layer, and the presentation layer, we can replace the web page with a winfrom form, as long as the ** of the presentation layer is modified, the other layers do not need to be moved, 2Distributed computing is possible, and for large ***, we can put these three layers on different servers, so that it will be faster to access.

That's all.

In general, the three-tier architecture divides the entire business application into the presentation layer (UI), the business logic layer (BLL), and the data access layer (DAL). The purpose of distinguishing hierarchies is the idea of "high cohesion, low coupling".

Presentation Layer (UI): Generally speaking, it is the interface presented to the user, that is, what the user sees when using a system. Business Logic Layer (BLL);

The operation for a specific problem can also be said to be the operation of the data layer and the processing of data business logic. Data Access Layer (DAL): The transactions made by this layer directly operate the database, and there is a vertical relationship between each layer for data addition, deletion, modification, update, and search.

The three-layer structure is a kind of N-layer structure, generally speaking, the layers are downward-dependent, and the upper layer cannot be developed before the lower layer determines its interface (contract), and the change of the lower layer interface (contract) will make the upper layer change together.

Advantages: The division of labor is clear, organized, easy to debug, and scalable.

Disadvantages: Increased cost of Shoyama Xiangbu.

1. Presentation layer (UI): Generally speaking, it is the interface presented to the user, that is, what the user sees when using a system.

2. Business logic layer (BLL): operation for specific problems, which can also be said to be the operation of the data layer, and the processing of data business logic.

3. Data access layer (DAL): The transactions made by this layer directly operate the database, and add, delete, modify, and search data for the data.

Three-tier architecture explained The so-called three-tier architecture is a middleware layer, also called a component layer, between the client and the database. The three-tier system mentioned here does not refer to the physical three-layer, not simply placing three machines is a three-layer architecture, nor is it only the BS application that is the three-layer architecture, the three-layer refers to the logical three-layer, even if the three layers are placed on one machine. The application of the three-layer system puts business rules, data access, legitimacy verification and other work in the middle layer for processing.

Typically, the client does not interact directly with the database, but establishes a connection to the middle tier via COM dcom communication, and then exchanges with the database through the middle tier.

Understand the three-tier structure.

We use the three-layer structure mainly to make the project structure clearer and the division of labor clearer, which is conducive to later maintenance and upgrading

The three-tier structure consists of the presentation layer (USL), the business logic layer (BLL), and the data access layer (DAL).

Refers to raw data, that is, an operation on the data, rather than a database, that provides data services to the business logic or presentation layer.

2: Business logic layer: It is mainly an operation for specific problems, which can also be understood as an operation on the data layer and a logic for data business.

If the data judgment layer is to dig Xunxiang building blocks, then the logic layer is the construction of these building blocks.

3: Chang leak representation layer: mainly represents the web mode, can also be expressed as the winform mode, and the web mode can also be expressed as.

aspx, if the logic layer is quite powerful and perfect, the logic layer can be perfected regardless of how the presentation layer is defined and changed.

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