MVC

MVC: model view controller ----- > model view controller

1. Structure of previous years

When the user understands the access control layer, the control layer can directly operate the database

Servlet -- crud -- > Database

Disadvantages: the program is very bloated, which is not conducive to maintenance

Servlet Code: processing request, response, jump request, JDBC, business code and logic code

Architecture: if there is no explanation, it can't be solved by adding one layer! (for example: JDBC)

2. MVC three-tier architecture

1. Model

2. View

3. Conroller(Servlet)

4. Take login as an example