Symfony 3.2 A circular reference has been detected

问题:

I have this two entities in my project

class PoliceGroupe
{
    /**
     * @var int
     *
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    private $id;

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

    /**
     * @ORM\ManyToMany(targetEntity="PointVente", inversedBy="policegroupe")
     * @ORM\JoinTable(name="police_groupe_point_vente",
     *      joinColumns={@ORM\JoinColumn(name="police_groupe_id", referencedColumnName="id")},
     *      inverseJoinColumns={@ORM\JoinColumn(name="point_vente_id", referencedColumnName="id")}
     *      )
     */
    private $pointVente;
    /**
     * Constructor
     */
    public function __construct($produit)
    {
       $this->pointVente = new \Doctrine\Common\Collections\ArrayCollection();
    }
}

And here is my other entity

class PointVente
{
    /**
     * @var string
     *
     * @ORM\Column(name="abb", type="string", length=50)
     */
    private $abb;

    /**
     * @var string
     *
     * @ORM\Column(name="libelle", type="string", length=255)
     */
    private $libelle;

    /**
     *
     * @ORM\ManyToMany(targetEntity="PoliceGroupe", mappedBy="pointVente")
     */
    private $policegroupe;
    }

and i'm trying to run this code in my controller

$encoders = array(new XmlEncoder(), new JsonEncoder());
$normalizers = array(new ObjectNormalizer());
$serializer = new Serializer($normalizers, $encoders);
$em = $this->getDoctrine()->getManager();
$data = $request->get('data');
$policegroupe=$em->getRepository('StatBundle:PoliceGroupe')->findOneBy(array('id' => $data));
$pointventes = $policegroupe->getPointVente();
$jsonContent = $serializer->serialize($pointventes, 'json');
return new JsonResponse( array('pointventes'=>$jsonContent) );

But I get this exception

Symfony\Component\Serializer\Exception\CircularReferenceException: A circular reference has been detected (configured limit: 1).
    at n/a
        in C:\wamp\www\Sys\vendor\symfony\symfony\src\Symfony\Component\Serializer\Normalizer\AbstractNormalizer.php line 194

I mapped my entities according to the doctrine annotations. Am I missing something?

回答1:

Symfony 3.2

Use the useCircularReferenceLimit method. For example:

$normalizer = new ObjectNormalizer();
$normalizer->setCircularReferenceLimit(2);
// Add Circular reference handler
$normalizer->setCircularReferenceHandler(function ($object) {
    return $object->getId();
});
$normalizers = array($normalizer);
$serializer = new Serializer($normalizers, $encoders);

The reason is that the circular referencing in your entities causes some problems when you try to serialize them. The effect of the method is to define the maximum depth of the serialization hierarchy.

Edit: Added circular reference handler (A circular reference has been detected (configured limit: 1) Serializer SYMFONY)

EDIT : Update (Symfony 4.2)

To be tried with Symfony 3.2, but the circular_reference_limit is not the problem here (and the defaults to 1 is OK, else your entity will be retrieved 2 times), the problem is the way the entity is handled by circular_reference_handler. Telling that id is the entity identifier solves the problem. See Symfony Docs at the bottom of this paragraph.

Since setCircularReferenceHandler is deprecated in favour of the following keys of the context circular_reference_handler, we can write:

// Tip : Inject SerializerInterface $serializer in the controller method
// and avoid these 3 lines of instanciation/configuration
$encoders = [new JsonEncoder()]; // If no need for XmlEncoder
$normalizers = [new ObjectNormalizer()];
$serializer = new Serializer($normalizers, $encoders);

// Serialize your object in Json
$jsonObject = $serializer->serialize($objectToSerialize, 'json', [
    'circular_reference_handler' => function ($object) {
        return $object->getId();
    }
]);

// For instance, return a Response with encoded Json
return new Response($jsonObject, 200, ['Content-Type' => 'application/json']);

回答2:

Fixed same issue by

use JMS\Serializer\SerializerBuilder;
...

$products = $em->getRepository('AppBundle:Product')->findAll();
$serializer = SerializerBuilder::create()->build();
$jsonObject = $serializer->serialize($products, 'json');

Read here