Deep Dive into Spring MVC Request Processing Flow

Spring MVC Process Overview

Spring MVC is a frequent interview topic in China; this article provides a concise yet thorough walkthrough of its source code to help readers understand the underlying mechanics.

Diagram

Code Location

The entry point is com.interface21.web.servlet.DispatcherServlet#doService , the original Spring 1.0 implementation that remains conceptually simple.

1. Set Request 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. Resolve Handler Execution Chain

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

3. Obtain HandlerAdapter

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

The HandlerAdapter interface is intended for framework developers, not application programmers; it allows custom workflow handling.

4. Execute Pre‑Handle Interceptors

// 4. Loop through handler's pre 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 Actual Handler

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

6. Execute Post‑Handle Interceptors

// 6. Loop through handler's post 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 the View

View view = null;
if (mv.isReference()) {
    // We need to resolve this view name
    // 7. Resolve View instance from ModelAndView
    view = this.viewResolver.resolveViewName(mv.getViewName(), locale);
}

8. Render the View

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

In summary, the DispatcherServlet orchestrates attribute setup, handler lookup, adapter delegation, interceptor chains, handler execution, view resolution, and final rendering.

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