code: private boolean preHandle(HttpRequest request, HttpResponse response, RequestHandler handler) throws Exception {
          for (HandlerInterceptor interceptor : mInterceptorList) {
              if (interceptor.onIntercept(request, response, handler)) return true;
          }
          return false;
      }
docs: Intercept the execution of a handler.
  
  @param request current request.
  @param response current response.
  @param handler the corresponding handler of the current request.
  
  @return true if the interceptor has processed the request and responded.