SpringMvc的请求入口：web.xml中的DispatcherServlet

        
     
      springServlet
         
     
      org.springframework.web.servlet.DispatcherServlet
     
         
      
       contextConfigLocation
          
      
       classpath*:spring-mvc.xml
      
         
     
      1
     
    
        
     
      springServlet
         
     
      *.html
     
    

调用DispatcherServlet的doService方法

protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {        if (logger.isDebugEnabled()) {            String resumed = WebAsyncUtils.getAsyncManager(request).hasConcurrentResult() ? " resumed" : "";            logger.debug("DispatcherServlet with name '" + getServletName() + "'" + resumed +                    " processing " + request.getMethod() + " request for [" + getRequestUri(request) + "]");        }        // Keep a snapshot of the request attributes in case of an include,        // to be able to restore the original attributes after the include.        Map
    
      attributesSnapshot = null;        if (WebUtils.isIncludeRequest(request)) {            attributesSnapshot = new HashMap
     
      ();            Enumeration
       attrNames = request.getAttributeNames();            while (attrNames.hasMoreElements()) {                String attrName = (String) attrNames.nextElement();                if (this.cleanupAfterInclude || attrName.startsWith("org.springframework.web.servlet")) {                    attributesSnapshot.put(attrName, request.getAttribute(attrName));                }            }        }        // Make framework objects available to handlers and view objects.        request.setAttribute(WEB_APPLICATION_CONTEXT_ATTRIBUTE, getWebApplicationContext());        request.setAttribute(LOCALE_RESOLVER_ATTRIBUTE, this.localeResolver);        request.setAttribute(THEME_RESOLVER_ATTRIBUTE, this.themeResolver);        request.setAttribute(THEME_SOURCE_ATTRIBUTE, getThemeSource());        FlashMap inputFlashMap = this.flashMapManager.retrieveAndUpdate(request, response);        if (inputFlashMap != null) {            request.setAttribute(INPUT_FLASH_MAP_ATTRIBUTE, Collections.unmodifiableMap(inputFlashMap));        }        request.setAttribute(OUTPUT_FLASH_MAP_ATTRIBUTE, new FlashMap());        request.setAttribute(FLASH_MAP_MANAGER_ATTRIBUTE, this.flashMapManager);        try {             doDispatch(request, response);         }        finally {            if (!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {                // Restore the original attribute snapshot, in case of an include.                if (attributesSnapshot != null) {                    restoreAttributesAfterInclude(request, attributesSnapshot);                }            }        }    }
     
    

调用DispatcherServlet的doDispatch方法，

processedRequest = checkMultipart(request);                multipartRequestParsed = (processedRequest != request);                // Determine handler for the current request.                mappedHandler = getHandler(processedRequest);                if (mappedHandler == null || mappedHandler.getHandler() == null) {                    noHandlerFound(processedRequest, response);                    return;                }                // Determine handler adapter for the current request.                HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());                // Process last-modified header, if supported by the handler.                String method = request.getMethod();                boolean isGet = "GET".equals(method);                if (isGet || "HEAD".equals(method)) {                    long lastModified = ha.getLastModified(request, mappedHandler.getHandler());                    if (logger.isDebugEnabled()) {                        logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified);                    }                    if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {                        return;                    }                }                if (!mappedHandler.applyPreHandle(processedRequest, response)) {                    return;                }                // Actually invoke the handler.                mv = ha.handle(processedRequest, response, mappedHandler.getHandler());                if (asyncManager.isConcurrentHandlingStarted()) {                    return;                }                applyDefaultViewName(processedRequest, mv);                mappedHandler.applyPostHandle(processedRequest, response, mv);

获取mappedHandler，mappedHandler里面已经有了具体的Controller和方法

// Determine handler for the current request.                mappedHandler = getHandler(processedRequest);                if (mappedHandler == null || mappedHandler.getHandler() == null) {                    noHandlerFound(processedRequest, response);                    return;                }

获取HandlerAdapter

// Determine handler adapter for the current request.                HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

方法执行前的intercepter,比如aop拦截

if (!mappedHandler.applyPreHandle(processedRequest, response)) {                    return;                }

执行方法

// Actually invoke the handler.                mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

方法结束后的intercepter

mappedHandler.applyPostHandle(processedRequest, response, mv);

解析结果，对报错和视图处理

processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);

总结

1、请求进入DispatchServlet

2、通过handlermapping找到对应的handler

3、找到handlerAdapter

4、执行pre Intercepter

5、执行具体的方法

6、执行post Intercepter

7、解析视图返回