Symfony + JMSSerializer throw 500 - handleCircularReference - symfony

Question

I'm trying to use the JMSSerializer with Symfony to build a simple json api.
So i have 2 simple Entities (1 User can have many Cars, each Car belongs to one User):
class Car
{
/**
* #ORM\Id()
* #ORM\GeneratedValue()
* #ORM\Column(type="integer")
*/
private $id;
/**
* #ORM\Column(type="string", length=255)
*/
private $name;
/**
* #ORM\ManyToOne(targetEntity="App\Entity\User", inversedBy="cars")
* #ORM\JoinColumn(nullable=false)
*/
private $user;
}
class User extends BaseUser
{
/**
* #ORM\Id
* #ORM\Column(type="integer")
* #ORM\GeneratedValue(strategy="AUTO")
*/
protected $id;
/**
* #ORM\OneToMany(targetEntity="App\Entity\Car", mappedBy="user", orphanRemoval=true)
*/
private $cars;
}
Now i want to get all Cars with their User.
My Controller:
class CarController extends AbstractController
{
/**
* #param CarRepository $carRepository
*
* #Route("/", name="car_index", methods="GET")
*
* #return Response
*/
public function index(CarRepository $carRepository)
{
$cars = $carRepository->findAll();
$serializedEntity = $this->container->get('serializer')->serialize($cars, 'json');
return new Response($serializedEntity);
}
}
This will throw a 500 error:
A circular reference has been detected when serializing the object of
class \"App\Entity\Car\" (configured limit: 1)
Ok, sounds clear. JMS is trying to get each car with the user, and go to the cars and user ....
So my question is: How to prevent this behaviour? I just want all cars with their user, and after this, the iteration should be stopped.

Answer 1

You need to add max depth checks to prevent circular references.
This can be found in the documentation here
Basically you add the #MaxDepth(1) annotation or configure max_depth if you're using XML/YML configuration. Then serialize like this:
use JMS\Serializer\SerializationContext;
$serializer->serialize(
$data,
'json',
SerializationContext::create()->enableMaxDepthChecks()
);
Example Car class with MaxDepth annotation:
class Car
{
/**
* #\JMS\Serializer\Annotation\MaxDepth(1)
*
* [..]
*/
private $user;