MVC three-tier architecture understanding

MVC Three layer architecture

1. What is? MVC？

• Model View Controller Model 、 View 、 controller

2.MVC Three layer architecture

2.1、 Earlier years

• controller ：Controller-----Servlet
  • Receive requests from users
  • Respond to client content
  • Redirect or forward

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Servlet and JSP Can write Java Code , For ease of maintenance and use ,Servlet Focus on processing requests , And control view jump ;JSP Focus on displaying data

• View layer ：View-----JSP

  • Display data
  • Provide requests that we can operate

• JavaBean---->jdbc-----> database

3. Earlier years , User direct access control layer , The control layer can directly operate the database ;

• disadvantages ： The program is very bloated , Not conducive to maintenance ;Servlet In the code of ： Processing requests 、 Respond to 、 View jump 、 Handle JDBC、 Deal with business code 、 Processing logic code

2.2、 Now? （ If one floor is not enough, add another ）

1. controller

• controller ：Controller Servlet
  • Receive requests from users
  • Leave it to the business layer to do ----->service
  • View jump ------>JSP( Forward or redirect to the front end of the view layer )

2. View layer

• View ： View layer JSP
  • Show the data model
  • Provide user operation

3. Model

• Service

  • login
  • logout
  • Query all users ------->javabean

• javabean ---->JDBC ------> database

• Model： Control business operations 、 Save the data 、 Modifying data 、 Delete data , Query data

service----->DAO----->JDBC------> database

4. summary

• Model：

  • Business processing ： Business logic （Service）
  • Data persistence layer ：CRUD（ Additions and deletions ）

• View：

  • Display data
  • Provide links , launch Servlet request

• Controller：

  • Receive requests from users ：（req： Request parameters 、Session： Information …）
  • Give it to the business layer to process the corresponding code
  • Control the jump of the view

   Sign in ---> Receive login requests from users ---> Handle user requests （ Get user login parameters ,username,password）-----> Leave it to the business layer to handle the login business （ Determine whether the user name and password are correct ）  ----->Dao The layer queries whether the user name and password are correct -----> Database search 
  

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