code: protected boolean isPreFlightRequest(HttpServletRequest request) {
          return (isCorsRequest(request)
                  && MethodType.OPTIONS.name().equals(request.getMethod())
                  && request.getHeader(HttpHeaders.ACCESS_CONTROL_REQUEST_METHOD) != null);
      }
docs: Returns {@code true} if the request is a valid CORS pre-flight one.
  
  @param request the http request
  @return {@code true} if the request is a valid CORS pre-flight one, else {@code false}