Mastering Spring MVC: Step-by-Step Flow and Core Code Explained

Spring MVC Process

First, a diagram:

Code location: com.interface21.web.servlet.DispatcherServlet#doService The original Interface21 code is a minimal implementation of Spring MVC; modern Spring has grown much larger, but Interface21 remains an excellent learning reference.

1. Set Attributes

// 1. Set attributes
// Make web application context available
request.setAttribute(WEB_APPLICATION_CONTEXT_ATTRIBUTE, getWebApplicationContext());

// Make locale resolver available
request.setAttribute(LOCALE_RESOLVER_ATTRIBUTE, this.localeResolver);

// Make theme resolver available
request.setAttribute(THEME_RESOLVER_ATTRIBUTE, this.themeResolver);

2. Find Handler and Execution Chain

// 2. Find handler and return execution chain
HandlerExecutionChain mappedHandler = getHandler(request);

3. Get Handler Adapter

// This will throw an exception if no adapter is found
// 3. Return handler's adapter
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

HandlerAdapter is intended for framework developers, not application developers; it allows custom web‑workflow implementations.

public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object delegate)
    throws IOException, ServletException {
    // you may need to doSomething...
    ((MyHandler) delegate).doSomething(request);
    return null;
}

4. Execute Pre‑handle Interceptors

for (int i = 0; i < mappedHandler.getInterceptors().length; i++) {
    HandlerInterceptor interceptor = mappedHandler.getInterceptors()[i];
    // pre interceptor
    if (!interceptor.preHandle(request, response, mappedHandler.getHandler())) {
        return;
    }
}

5. Invoke the Real Handler and Obtain ModelAndView

// 5. Execute the real handler and get ModelAndView (handler may be a proxy, possibly with AOP)
ModelAndView mv = ha.handle(request, response, mappedHandler.getHandler());

6. Execute Post‑handle Interceptors

for (int i = mappedHandler.getInterceptors().length - 1; i >= 0; i--) {
    HandlerInterceptor interceptor = mappedHandler.getInterceptors()[i];
    // post interceptor
    interceptor.postHandle(request, response, mappedHandler.getHandler());
}

7. Resolve View from ModelAndView

View view = null;
if (mv.isReference()) {
    // We need to resolve this view name
    view = this.viewResolver.resolveViewName(mv.getViewName(), locale);
}

8. Render the View

// 8. Render view and return
view.render(mv.getModel(), request, response);