Symfony json body to request object auto mapping

ConstraintViolationsConverter.php

<?php

namespace App\Request\ParamConverter;

use Sensio\Bundle\FrameworkExtraBundle\Configuration\ParamConverter;
use Sensio\Bundle\FrameworkExtraBundle\Request\ParamConverter\ParamConverterInterface;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\Validator\ConstraintViolationListInterface;

final class ConstraintViolationsConverter implements ParamConverterInterface
{
    /**
     * @param Request $request
     * @param ParamConverter $configuration
     *
     * @return bool|void
     */
    public function apply(Request $request, ParamConverter $configuration)
    {
        $violations = $request->attributes->get('_violations');
        $request->attributes->remove('_violations');

        $request->attributes->set($configuration->getName(), $violations);
    }

    /**
     * @param ParamConverter $configuration
     *
     * @return bool
     */
    public function supports(ParamConverter $configuration)
    {
        return ConstraintViolationListInterface::class === $configuration->getClass();
    }
}

ExampleController.php

<?php

namespace App\Controller;

final class ExampleController extends AbstractController
{
    public function registerAction(
        RegistrationRequest $registrationRequest,
        ConstraintViolationListInterface $violations,
        Registration $registration
    ): Response {
        if ($violations->count() > 0) {
            return $this->validationError($violations);
        }
        //...

        return $this->json(..);
    }
}

JsonBodySerializableConverter.php

<?php

namespace App\Request\ParamConverter;

use Sensio\Bundle\FrameworkExtraBundle\Configuration\ParamConverter;
use Sensio\Bundle\FrameworkExtraBundle\Request\ParamConverter\ParamConverterInterface;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\Serializer\SerializerInterface;
use Symfony\Component\Validator\Validator\ValidatorInterface;

final class JsonBodySerializableConverter implements ParamConverterInterface
{
    /**
     * @var SerializerInterface
     */
    private $serializer;

    /**
     * @var ValidatorInterface
     */
    private $validator;

    /**
     * @param SerializerInterface $serializer
     * @param ValidatorInterface $validator
     */
    public function __construct(SerializerInterface $serializer, ValidatorInterface $validator)
    {
        $this->serializer = $serializer;
        $this->validator = $validator;
    }

    /**
     * @param Request $request
     * @param ParamConverter $configuration
     *
     * @return bool|void
     */
    public function apply(Request $request, ParamConverter $configuration)
    {
        $body = $request->getContent();

        $obj = $this->serializer->deserialize($body, $configuration->getClass(), 'json');
        $violationList = $this->validator->validate($obj);

        $request->attributes->set('_violations', $violationList);
        $request->attributes->set($configuration->getName(), $obj);
    }

    /**
     * @param ParamConverter $configuration
     *
     * @return bool
     */
    public function supports(ParamConverter $configuration)
    {
        $class = $configuration->getClass();
        if (!is_string($class)) {
            return false;
        }

        return in_array(JsonBodySerializableInterface::class, class_implements($class));
    }
}

RegistrationRequest.php

<?php

namespace App\Request;

use App\Request\ParamConverter\JsonBodySerializableInterface;
use Symfony\Component\Serializer\Normalizer\DenormalizableInterface;
use Symfony\Component\Serializer\Normalizer\DenormalizerInterface;
use Symfony\Component\Validator\Constraints as Assert;

final class RegistrationRequest implements JsonBodySerializableInterface
{
    /**
     * @Assert\NotBlank
     * @Assert\Type("string")
     *
     * @var string
     */
    public $username;

    /**
     * @Assert\NotBlank
     * @Assert\Type("string")
     *
     * @var string
     */
    public $email;
}

both JsonBodySerializableInterface is missing but thanks for sharing the converters anyway