使用Symfony4和FOSRESTBundle通过REST API上传文件

Question

我正在使用Symfony4，FOSRestBundle和Symfony / Serializer构建REST API。 当我尝试提交表单时，收到验证错误“请上传文件”。 因此，我使用Controller而非FOSRestController创建了另一种表单。另外，我已将$form->submit($request->request->all())替换为$form->handleRequest($request)。而且有效！ 因此，我认为问题出在$form->submit($request->request->all())。 如何使用Symfony4和FOSRESTBundle通过API上传文件？

应用程序\实体\用户：

        /**
         * @ORM\Entity(repositoryClass="App\Repository\UserRepository")
         */
        class User
        {
            // ...

            /**
             * @ORM\Column(type="string", length=255)
             * @Assert\NotBlank(message="Please, upload the file.")
             * @Assert\File(maxSize="50000k", mimeTypes={ "application/pdf", "application/vnd.ms-powerpoint" })
             */
            private $file;

            public function getFile()
            {
                return $this->file;
            }

            public function setFile($file): self
            {
                $this->file = $file;

                return $this;
            }

            // ...
        }

App \ Form \ UserType

        class UserType extends AbstractType
        {
            public function buildForm(FormBuilderInterface $builder, array $options)
            {
                $builder->add('file', FileType::class);
            }

            public function configureOptions(OptionsResolver $resolver)
            {
                $resolver->setDefaults([
                    'data_class' => User::class,
                    'csrf_protection' => false
                ]);
            }
        }

App \ Controller \ UserController

    class UserController extends FOSRestController
    {
        public function postUserAction(Request $request)
        {
            $user = new User();

            $form = $this->createForm(UserType::class, $user);
            $data = json_decode($request->request->all(), true);
            $form->submit($data);

            if ($form->isSubmitted() && $form->isValid()) {
                $file = $user->getFile();
                $fileName = $this->generateUniqueFileName().'.'.$file->guessExtension();
                $file->move(
                    $this->getParameter('file_directory'),
                    $fileName
                );
                $user->setFile($fileName);

                $em = $this->getDoctrine()->getManager();
                $em->persist($user);
                $em->flush();
                return $this->handleView($this->view(['status' => 'created'], Response::HTTP_CREATED, ['Access-Control-Allow-Origin' => '*']));
            }
            return $this->handleView($this->view($form->getErrors(true, false)));
        }
    }