Spring MVC Request Handling Flow: From DispatcherServlet to View Rendering

The request handling flow of Spring MVC is a classic interview question.

Complete Flow

HTTP Request
    ↓
DispatcherServlet (Front Controller)
    ↓
HandlerMapping (Find the handler)
    ↓
HandlerAdapter (Invoke the handler)
    ↓
Handler (Controller method)
    ↓
ModelAndView (Return result)
    ↓
ViewResolver (Resolve the view)
    ↓
View (Render the view)
    ↓
HTTP Response

Detailed Explanation of Each Step

1. DispatcherServlet: The core of Spring MVC and the entry point for all requests. It is configured in web.xml or via AbstractAnnotationConfigDispatcherServletInitializer.

2. HandlerMapping: Finds the corresponding Controller method based on the request URL. The information from the @RequestMapping annotation is stored here. A common implementation is RequestMappingHandlerMapping.

3. HandlerAdapter: An adapter that invokes the Handler method. Since a Handler may return different types of values (ModelAndView, String, ResponseEntity, etc.), the adapter handles them uniformly.

4. ViewResolver: Resolves a logical view name ("userList") into a physical view ("/WEB-INF/views/userList.jsp").

Interceptor vs Filter

• Filter: Operates at the Servlet level and executes before the request enters DispatcherServlet
• Interceptor: Operates at the Spring level and executes after HandlerMapping but before HandlerAdapter

Interview Talking Points

An HTTP request first arrives at DispatcherServlet, which uses HandlerMapping to find the corresponding Controller method, invokes the method via HandlerAdapter and processes the return value, and finally resolves the view through ViewResolver or directly returns data.

Mastering this flow is your first step toward understanding "what happens behind the scenes in Spring Boot."