Deserialize an entity with a relationship with Symfony Serializer Component

I'm trying to deserialize an entity with a relationship using the symfony serializer component. This is my entity:

namespace AppBundle\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * Document
 *
 * @ORM\Table(name="document")
 * @ORM\Entity(repositoryClass="AppBundle\Repository\DocumentRepository")
 */
class Document
{
    /**
     * @var int
     *
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    private $id;

    /**
     * @ORM\ManyToOne(targetEntity="Genre", inversedBy="documents")
     * @ORM\JoinColumn(name="id_genre", referencedColumnName="id")
     */
    private $genre;

    /**
     * @var string
     *
     * @ORM\Column(name="name", type="string", length=100)
     */
    private $name;

    //getters and setters down here
    ...
}
    

And the Genre entity:

namespace AppBundle\Entity;

use Doctrine\ORM\Mapping as ORM;
use Doctrine\Common\Collections\ArrayCollection;

/**
 * Genre
 *
 * @ORM\Table(name="genre")
 * @ORM\Entity(repositoryClass="AppBundle\Repository\GenreRepository")
 */
class Genre
{
    /**
     * @var int
     *
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    private $id;

    /**
     * @var string
     *
     * @ORM\Column(name="name", type="string", length=50, nullable=true)
     */
    private $name;

    /**
     * @ORM\OneToMany(targetEntity="Document", mappedBy="genre")
     */
    private $documents;

    public function __construct()
    {
        $this->documents= new ArrayCollection();
    }

    //getters and setters down here
    ....
}

In my controller action right now I'm trying this:

$encoders = array(new JsonEncoder());
$normalizers = array(new ObjectNormalizer());
$serializer = new Serializer($normalizers, $encoders);

$document = $serializer->deserialize($request->getContent(), 'AppBundle\Entity\Document', 'json');

And my json data:

{"name": "My document", "genre": {"id": 1, "name": "My genre"}}

But I got the next error:

Expected argument of type "AppBundle\Entity\Genre", "array" given (500 Internal Server Error)

Is possible to deserialize a json request with an entity with relations inside?

Yes and no. First, you shouldn't re-create a new instance of the serializer in your controller but use the serializer service instead.

Second, no it's not possible out of the box with Symfony serializer. We are doing it in https://api-platform.com/ but there is a bit of magic there. That said, a PR has been made to support it: https://github.com/symfony/symfony/pull/19277