• 1、根据当前请求，找到可以处理请求的handler以及handler的所有拦截器
  • 2、先来循序执行所有拦截器的preHandle方法
    • 1、如果当前preHandle返回true，则执行下一个拦截器的preHandle方法
    • 2、如果当前preHandle返回false，则倒序执行afterCompletion方法
  • 3、如果任何一个拦截器返回false，直接跳出不执行目标方法
  • 4、所有拦截器都返回true，执行目标方法
  • 5、倒序执行所有拦截器的postHandle方法。
  • 6、前面的步骤有任何异常都会直接触发afterCompletion
  • 7、最终在页面渲染完成之后会倒序执行拦截器afterCompletion方法

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执行处源码DispatchServlet

  1.     @SuppressWarnings("deprecation")
  2.     protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
  3.         HttpServletRequest processedRequest = request;
  4.         HandlerExecutionChain mappedHandler = null;
  5.         boolean multipartRequestParsed = false;
  7.         WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
  9.         try {
  10.             ModelAndView mv = null;
  11.             Exception dispatchException = null;
  13.             try {
  14.                 processedRequest = checkMultipart(request);
  15.                 multipartRequestParsed = (processedRequest != request);
  17.                 // Determine handler for the current request.
  18.                 mappedHandler = getHandler(processedRequest);
  19.                 if (mappedHandler == null) {
  20.                     noHandlerFound(processedRequest, response);
  21.                     return;
  22.                 }
  24.                 // Determine handler adapter for the current request.
  25.                 HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
  27.                 // Process last-modified header, if supported by the handler.
  28.                 String method = request.getMethod();
  29.                 boolean isGet = HttpMethod.GET.matches(method);
  30.                 if (isGet || HttpMethod.HEAD.matches(method)) {
  31.                     long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
  32.                     if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
  33.                         return;
  34.                     }
  35.                 }
  37.                 if (!mappedHandler.applyPreHandle(processedRequest, response)) {
  38.                     return;
  39.                 }
  41.                 // Actually invoke the handler.
  42.                 mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
  44.                 if (asyncManager.isConcurrentHandlingStarted()) {
  45.                     return;
  46.                 }
  48.                 applyDefaultViewName(processedRequest, mv);
  49.                 mappedHandler.applyPostHandle(processedRequest, response, mv);
  50.             }
  51.             catch (Exception ex) {
  52.                 dispatchException = ex;
  53.             }
  54.             catch (Throwable err) {
  55.                 // As of 4.3, we're processing Errors thrown from handler methods as well,
  56.                 // making them available for @ExceptionHandler methods and other scenarios.
  57.                 dispatchException = new NestedServletException("Handler dispatch failed", err);
  58.             }
  59.             processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
  60.         }
  61.         catch (Exception ex) {
  62.             triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
  63.         }
  64.         catch (Throwable err) {
  65.             triggerAfterCompletion(processedRequest, response, mappedHandler,
  66.                     new NestedServletException("Handler processing failed", err));
  67.         }
  68.         finally {
  69.             if (asyncManager.isConcurrentHandlingStarted()) {
  70.                 // Instead of postHandle and afterCompletion
  71.                 if (mappedHandler != null) {
  72.                     mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
  73.                 }
  74.             }
  75.             else {
  76.                 // Clean up any resources used by a multipart request.
  77.                 if (multipartRequestParsed) {
  78.                     cleanupMultipart(processedRequest);
  79.                 }
  80.             }
  81.         }
  82.     }
  1.     boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {
  2.         for (int i = 0; i < this.interceptorList.size(); i++) {
  3.             HandlerInterceptor interceptor = this.interceptorList.get(i);
  4.             if (!interceptor.preHandle(request, response, this.handler)) {
  5.                 triggerAfterCompletion(request, response, null);
  6.                 return false;
  7.             }
  8.             this.interceptorIndex = i;
  9.         }
  10.         return true;
  11.     }
  1.     void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, @Nullable Exception ex) {
  2.         for (int i = this.interceptorIndex; i >= 0; i--) {
  3.             HandlerInterceptor interceptor = this.interceptorList.get(i);
  4.             try {
  5.                 interceptor.afterCompletion(request, response, this.handler, ex);
  6.             }
  7.             catch (Throwable ex2) {
  8.                 logger.error("HandlerInterceptor.afterCompletion threw exception", ex2);
  9.             }
  10.         }
  11.     }
  1.     /**
  2.      * Apply postHandle methods of registered interceptors.
  3.      */
  4.     void applyPostHandle(HttpServletRequest request, HttpServletResponse response, @Nullable ModelAndView mv)
  5.             throws Exception {
  7.         for (int i = this.interceptorList.size() - 1; i >= 0; i--) {
  8.             HandlerInterceptor interceptor = this.interceptorList.get(i);
  9.             interceptor.postHandle(request, response, this.handler, mv);
  10.         }
  11.     }