DispatcherServlet trong Spring MVC hoạt động như thế nào?

DispatcherServlet là Front Controller của Spring MVC — mọi HTTP request đều qua đây trước.

Flow:

HTTP Request
    ↓
DispatcherServlet
    ↓ 1. HandlerMapping → tìm controller method phù hợp
    ↓ 2. HandlerAdapter → gọi method (convert args, apply interceptors)
    ↓ 3. Controller method chạy
    ↓ 4a. @ResponseBody → MessageConverter (Jackson) → JSON
    ↓ 4b. view name → ViewResolver → template render → HTML
    ↓
HTTP Response

Các component:
- HandlerMapping — map URL pattern → handler method.
- HandlerAdapter — gọi method với argument đúng type.
- HandlerInterceptor — pre/post xử lý (auth check, logging).
- ViewResolver — tìm template từ view name.
- MessageConverter (Jackson) — serialize object → JSON.

Auto-configured: Spring Boot tự config tất cả qua DispatcherServletAutoConfiguration — không cần khai báo thủ công.

DispatcherServlet is the Front Controller of Spring MVC — every HTTP request passes through it.

Flow:

HTTP Request
    ↓
DispatcherServlet
    ↓ 1. HandlerMapping → find matching controller method
    ↓ 2. HandlerAdapter → call method (convert args, apply interceptors)
    ↓ 3. Controller method runs
    ↓ 4a. @ResponseBody → MessageConverter (Jackson) → JSON
    ↓ 4b. view name → ViewResolver → render template → HTML
    ↓
HTTP Response

Key components:
- HandlerMapping — maps URL patterns to handler methods.
- HandlerAdapter — invokes the method with the right argument types.
- HandlerInterceptor — pre/post processing (auth checks, logging).
- ViewResolver — finds the template from a view name.
- MessageConverter (Jackson) — serialises objects to JSON.

Auto-configured: Spring Boot configures everything via DispatcherServletAutoConfiguration — no manual declaration needed.