MVC & Spring MVC

MVC

• MVC is a design pattern, not a specific technology. MVC = Model + View + Controller
  • Model：data + business state (also includes DTO,entities,domain objects)
  • View：what user sees
  • Controller：receives request, calls business logic

Spring MVC

• Spring MVC is a web application framework, the part of Spring that handles HTTP requests (web layer) So in your backend:

  Spring Boot
     ↓
  Spring MVC (web layer)
     ↓
  Your Controller code

• Spring MVC = DispatcherServlet + Controller mapping + Parameter binding + Response rendering

  • It is responsible for: receiving HTTP requests, routing them to controllers, binding parameters. returning responses (JSON / view)

  Core components inside Spring MVC

  Component	Role
  DispatcherServlet	entry point
  HandlerMapping	find controller
  HandlerAdapter	execute method
  Controller	business entry
  ViewResolver	render response

  Full request flow (Spring MVC core)

  1. Request arrives

     POST / coupon / claim;

  2. DispatcherServlet receives it

     • This is the entry point of Spring MVC
     • why DispatcherServlet is important?
       • All HTTP requests go through dispatcherServlet, it enables: unified request handling, interceptor support, exception handling, logging, security filters
     • Who creates DispatcherServlet?
       • In old Spring MVC (manual config) You had to configure it yourself:

         <servlet>
         <servlet-name>dispatcher</servlet-name>
         <servlet-class>DispatcherServlet</servlet-class>
         </servlet>

       • In Spring Boot
         • You do NOT create it manually, Spring Boot does it automatically using auto-configuration
         • Because you added:

           spring-boot-starter-web

           Spring Boot:
           • detects web dependency
           • creates DispatcherServlet
           • registers it
           • maps it to /

  3. Handler Mapping

     Spring finds:@PostMapping("/coupon/claim")→ maps映射 request to method

  4. Handler Adapter适配器

     Responsible for:

     • calling controller method
     • preparing parameters

  5. Parameter binding绑定

     @RequestBody ClaimRequest req    JSON → Java object

  6. Execute Controller

     couponService.claim(req);

  7. Return result

     return 'ok';

  8. View resolution / JSON conversion

     • If @RestController → JSON
     • If @Controller → HTML view

  9. Response sent

     HTTP 200 OK