org.springframework.web.servlet.DispatcherServlet#doDispatch

1.1 獲取執行呼叫鏈HandlerExecutionChain
1.2 獲取處理器介面卡HandlerAdapter
1.3 呼叫攔截器preHandle
1.4 呼叫介面卡的handle方法
1.5 處理檢視名
1.6 呼叫postHandle方法
1.7 檢視渲染

protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
   HttpServletRequest processedRequest = request;
 
   HandlerExecutionChain mappedHandler = null;
   boolean multipartRequestParsed = false;

   WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);

   try {
      ModelAndView mv = null;
      Exception dispatchException = null;

      try {

         // 檢查是否多模組請求
         processedRequest = checkMultipart(request);
 
         multipartRequestParsed = (processedRequest != request);

         // Determine handler for the current request.

         // 通過HandlerMapping根據url獲取HandlerMethod, 再獲取攔截器, 組合起來創建出呼叫執行鏈HandlerExecutionChain物件(HandlerMethod + 攔截器)
         mappedHandler = getHandler(processedRequest);
         if (mappedHandler == null) {
 
            noHandlerFound(processedRequest, response);
            return;
         }

         // Determine handler adapter for the current request.

         // 獲取處理器介面卡, 根據不同種類的介面卡支援程度supports方法, 獲取到合適的介面卡, 處理的核心方法為handle方法
         // mappedHandler.getHandler()獲取的是HandlerMethod物件
         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 (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
               return;
            }
         }

         // 處理攔截器preHandle方法
         if (!mappedHandler.applyPreHandle(processedRequest, response)) {
            return;
         }

         // Actually invoke the handler.

         // 呼叫HandlerAdapter的handle方法
         mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

         if (asyncManager.isConcurrentHandlingStarted()) {
            return;
         }

         // 處理檢視名字
         applyDefaultViewName(processedRequest, mv);

         // 處理攔截器postHandle方法
         mappedHandler.applyPostHandle(processedRequest, response, mv);
      }
      catch (Exception ex) {
         dispatchException = ex;
      }
      catch (Throwable err) {
         // As of 4.3, we're processing Errors thrown from handler methods as well,
         // making them available for @ExceptionHandler methods and other scenarios.
         dispatchException = new NestedServletException("Handler dispatch failed", err);
      }

      // 處理檢視渲染
      processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
   }
   catch (Exception ex) {
      triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
   }
   catch (Throwable err) {
      triggerAfterCompletion(processedRequest, response, mappedHandler,
            new NestedServletException("Handler processing failed", err));
   }
   finally {
      if (asyncManager.isConcurrentHandlingStarted()) {
         // Instead of postHandle and afterCompletion
         if (mappedHandler != null) {
            mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
         }
      }
      else {
         // Clean up any resources used by a multipart request.
         if (multipartRequestParsed) {
            cleanupMultipart(processedRequest);
         }
      }
   }
}