What is a three tier architecture? What are the main functions of each layer and their interrelation

A three-tier architecture in the usual sense.

It is to divide the entire business application into the following layers: presentation layer (UI), business logic layer (BLL), and data access layer (DAL). The purpose of distinguishing the hierarchy is to "high cohesion, low coupling."

thoughts. 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): Operations on specific problems, which can also be said to be operations on the data layer, and processing 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 adding, deleting, modifying, updating, and searching data. The three-layer structure is a kind of N-layer structure, generally speaking, the layers are downward-dependent, the lower layer is not determined before its interface (contract), the upper layer cannot be developed, and the change of the lower interface (contract) will make the upper layer change together.

Pros: Clear division of labor, clear organization, easy to debug, and scalability.

Cons: Increased cost. Beams.

The three-layer architecture (presentation layer, business logic layer, and data access layer) is not used in general software projects, such as applications, middleware, and data servers. It is now the mainstream architecture of general software projects. - SOA (ServiceOriented Architecture) is a service-oriented architecture, which is mainly a software development idea.

Develop and package corresponding programs according to the needs of different objects, and independently of the hardware platform, operating system and programming language that implements the service, which can effectively save investment and greatly improve the scalability of the software.

I despise the classmate who said that MVC is misleading. MVC is the design pattern, the three layers are the architecture, which three layers, many of the following students have explained very clearly. The display layer is the view layer, which is the reality of your data.

You can use Web Winform. Business Layer BLL Layer This layer is the business layer, and the transactions at this layer are mainly customer-facing. Data Layer Dal Layer This layer is the data layer, which is the layer that processes how your business layer processes data, relatively speaking, this layer is more programmer-oriented.

BLL does what you do DAL does what you do in the BLL layer.

Data layer, logic layer, presentation layer; As for the collective division, it is up to you to decide how many layers it is.

Presentation Layer (UI): The interface presented to the user;

Business Logic Layer (BLL): processes the business logic of data.

Data Access Layer (DAL): data is added, deleted, modified, and searched.

Presentation layer, business logic layer, and data access layer.

Applications typically have three layers: the presentation layer, the business layer, and the data layer, which is used to present the user interfaces, and the classes and objects of the business layer are used to "drive" these interfaces.

In , this layer includes ASPX pages, user controls, server controls, and certain security-related classes and objects.

Business Tier

The business layer is used to access the data layer, fetch data from the data layer, modify the data, delete the data, and return the results to the presentation layer.

In this layer, this layer includes using SQL Client or OLEDB to retrieve data from SQL Server or Access database, update data, delete data, and put the obtained data into DataReader or Dataset and return it to the presentation layer. The returned data may have only one integer number, such as the number of row records in a table, but this is also calculated using the data in the data layer.

The three-layer architecture includes the data access layer (DAL), the business logic layer (BLL) and the presentation layer (UI), and an entity layer is used for data transmission between the layers. If something goes wrong there, fix it there! Easy to check and easy to change!

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 layer is the building block, then the logic layer is the building block of these building blocks.

3: Presentation layer: It mainly represents the web mode, which can also be expressed in the Winform mode, and the web mode can also be expressed as the web mode.

aspx, if the logic layer is quite powerful and complete, the logic layer can be perfected no matter how the presentation layer is defined and changed.

Provision of Services.

Presentation layer: Mainly interacts with the user.

Business logic layer: Mainly business logic.

Data access layer: mainly interacts with the database.