symfony直接在控制器下使用 validator，就像laravel一样:

    public function eventPaperSubscribeAction(Request $request, Service\ScilitCommentManagementService $commentService, Entity\Paper $paper, ValidatorInterface $validator)
    {
        $email = $request->request->get('email');

        $constraints = [
            new \Symfony\Component\Validator\Constraints\Email(),
            new \Symfony\Component\Validator\Constraints\NotBlank(),
        ];

        $error = $validator->validate($email, $constraints);
        if (count($error) > 0) {
            return new JsonResponse(['success' => false, 'status' => 'ERROR', 'message' => 'Invalid email addresss']);
        }

        $validateSubscriber = $commentService->validateSubscriber($paper, $email);
        if (!$validateSubscriber['success']) {
            return new JsonResponse($validateSubscriber);
        }

        $subscribeUser = $commentService->subscribeUser($paper, $email, $this->getUser());

        return new JsonResponse($subscribeUser);
    }