protected function resolveValidator(Request $request)
    {
        if (! isset($this->validators[$request->getHandler()])) {
            return null;
        }

        try {
            $validatorClass = $this->validators[$request->getHandler()];
            return $this->container->make($validatorClass);
        } catch (BindingResolutionException $e) {
            return null;
        }
    }