About three-tier architecture and MVC

1、 Three layer architecture

Our development architecture is generally based on two forms , One is  C/S  framework , That's the client side / The server , The other is  B/S  framework , It's just

It's a browser server . stay  JavaEE  In development , Almost all based on  B/S  Architecture development . So in  B/S  Architecture , The three-tier architecture of the system standard

Include ： The presentation layer 、 The business layer 、 Persistence layer . The three-tier architecture is used very much in our actual development , So the cases in our course are all based on

Three tier architecture design .

In the three-tier architecture , Each layer performs its own functions , Next let's talk about what each layer is responsible for ：

The presentation layer ：

That's what we often say web layer . It is responsible for receiving client requests , Respond to client results , Usually the client uses http Protocol request

web  layer ,web  Need to receive  http  request , complete  http  Respond to .

The presentation layer includes the presentation layer and the control layer ： The control layer is responsible for receiving requests , The presentation layer is responsible for the presentation of the results .

The presentation layer depends on the business layer , When receiving the client request, the business layer will be called for business processing , And respond the processing result to the client .

The design of the presentation layer generally uses  MVC  Model .（MVC  It's the design model of the presentation layer , It has nothing to do with other layers ）

The business layer ：

That's what we often say  service  layer . It's responsible for business logic processing , It is closely related to the needs of our development projects .web  Layers depend on industry

Service level , But the business layer doesn't rely on  web  layer .

The business layer may rely on the persistence layer in business processing , If you want to persist data, you need to ensure transaction consistency .（ That's what we're talking about ,

Transactions should be placed at the business level to control ）

Persistence layer ：

That is what we often say  dao  layer . Responsible for data persistence , Including data layer that is database and data access layer , Database is to enter data into

The carrier of line persistence , Data access layer is the interface between business layer and persistence layer , The business layer needs to persist the data into the database through the data access layer . informally , The persistence layer is to interact with the database , Add, delete, modify and query the database table .

2、MVC  Model

MVC  The full name is  Model View Controller, It's a model (model)－ View (view)－ controller (controller) Abbreviation ,  Is a design creation  Web  Patterns in the application presentation layer .MVC  Each part of the ：

Model（ Model ）：

It usually refers to our data model . Functions are generally used to encapsulate data .

View（ View ）：

It usually means our  jsp  perhaps  html. The function is to show data .

Usually views are created from model data .

Controller（ controller ）：

Is the part of the application that handles user interaction . The function is generally to process program logic .

It's not well understood relative to the first two , Here's an example ：

for example ：

We want to save a user's information , The user information contains the name , Gender , Age and so on .

At this time, the form input requires that the age must be  1~100  Integer between . Name and gender cannot be blank . And fill in the data

Into the model .

At this time in addition to  js  In addition to the verification of , The server side should also have data accuracy verification , So calibration is what the controller should do

Of .

When the verification fails , The controller is responsible for displaying the error page to the user .

If the verification is successful , The controller is also responsible for filling the data into the model , And call the business layer to implement the complete business requirements .

key word ：

java train