在 JSON 中使用来自 OneToMany 关联的 Doctrine Collection 数据

Question

I've seen many examples of how to set up a OneToMany association between Entities. However, I have not seen anything on how to output the data from an association. (such as converting to JSON or just having a clean array)

So, here is some sample code:

declare(strict_types=1);

namespace Banks\Entity;

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

/**
 * https://www.doctrine-project.org/projects/doctrine-orm/en/2.6/reference/basic-mapping.html
 *
 * @ORM\Entity
 * @ORM\Table(name="bank")
 **/
class Banks implements \JsonSerializable
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer", name="id", nullable=false)
     * @ORM\GeneratedValue(strategy="IDENTITY")
     */
    protected $id;

    /**
     * A Bank could have Many Branches
     *
     * @ORM\OneToMany(targetEntity="Branches\Entity\Branches", mappedBy="bank")
     *
     */
    protected $branches;

    /**
     * @ORM\Column(type="string", nullable=true)
     */
    protected $name;

    /**
     *
     * @return array|mixed
     */
    public function jsonSerialize()
    {
        return [
            'id' => $this->id,
            'name' => $this->name,
            'branches' => $this->getBranches()
        ];
    }

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

    public function getBranches(): Collection
    {
        return $this->branches;
    }

    // ... Other getter/setters removed
}

Then we also have the Branches Entity:

declare(strict_types=1);

namespace Branches\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * https://www.doctrine-project.org/projects/doctrine-orm/en/2.6/reference/basic-mapping.html
 *
 * @ORM\Entity
 * @ORM\Table(name="branches")
 **/
class Branches implements \JsonSerializable
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer", nullable=false)
     * @ORM\GeneratedValue(strategy="IDENTITY")
     */
    protected $id;

    /**
     * A Branch has one Bank
     *
     * @ORM\ManyToOne(targetEntity="Banks\Entity\Banks", inversedBy="branches")
     * @ORM\JoinColumn(name="bank_id", referencedColumnName="id")
     */
    protected $bank;

    /**
     * @ORM\Column(type="integer", nullable=false)
     */
    protected $bank_id;

    /**
     * @ORM\Column(type="string", nullable=true)
     */
    protected $name;

    /**
     *
     * @return array|mixed
     */
    public function jsonSerialize()
    {
        return [
            'id' => $this->id,
            'bank_id' => $this->bank_id,
            'name' => $this->name,
            'bank' => $this->getBank()
        ];
    }

    public function getBank()
    {
        return $this->bank;
    }

    // ... Other getter/setters removed
}

Querying both Entities work fine overall, with calls to $result->jsonSerialize() , then returning with return new JsonResponse($result) to get a JSON object. Though querying a Branch has the expected result, where I receive the Branch along with the associated Bank as part of the output, the query to Bank is not returning the associated Branches and instead only displays as "branches": {}

I know this is because $branches is a Collection, but how to output it in a way to be part of the resulting JSON object?

I've tried $this->branches->toArray() , but that results in an array of Objects that cannot be encoded to JSON, therefore, ending in an error.

NOTE: The contents (Object) of $this->getBranches() does contain the Branches as expected, which can be seen by $this->branches->count() . But how to reach them in such a way to allow JsonSerializable to create the JSON?

As requested, here is middleware code leaving up to Entity usage:

A factory is used to create what is needed by the Handler:

class BanksViewHandlerFactory
{
    public function __invoke(ContainerInterface $container) : BanksViewHandler
    {
        $entityManager = $container->get(EntityManager::class);

        $entityManager->getConfiguration()->addEntityNamespace('Banks', 'Banks\Entity');

        $entityRepository = $entityManager->getRepository('Banks:Banks');

        return new BanksViewHandler($entityManager, $entityRepository);
    }
}

The Factory calls the Handler:

class BanksViewHandler implements RequestHandlerInterface
{
    protected $entityManager;
    protected $entityRepository;

    public function __construct(
        EntityManager $entityManager,
        EntityRepository $entityRepository,
    ) {
        $this->entityManager = $entityManager;
        $this->entityRepository = $entityRepository;
    }

    public function handle(ServerRequestInterface $request) : ResponseInterface
    {
        $return = $this->entityRepository->find($request->getAttribute('id'));

$result['Result']['Banks'] = $return->jsonSerialize();

        return new JsonResponse($result);
    }
}

The handler returns the JSON.

Answer 1

It's important to note that, when implementing the \\JsonSerializable interface, calling jsonSerialize() directly does not return JSON, and you do not call this method explicitly.

As stated in the docs:

Objects implementing JsonSerializable can customize their JSON representation when encoded with json_encode().

The intent of implementing this interface is to enforce the jsonSerialize() method, which is called internally when passing the object(s) to json_encode() ; eg:

$result = $banksRepository->find($id);
$json = json_encode($result);

Additionally, if you want to serialize the child Branch entities as well you need to:

1. Implement \\JsonSerializable for this entity (which you have done)
2. Doctrine will return these Branches as an ArrayCollection object, containing all child Branch objects. In order to ensure that json_encode() encodes these to JSON properly you need to convert the ArrayCollection to an array using toArray() .

To illustrate - (as you pointed out you also implemented this):

public function jsonSerialize()
{
    return [
        'id' => $this->id,
        'name' => $this->name,
        'branches' => $this->getBranches()->toArray(), // <-- 
    ];
}

This should serialise your Bank and associated Branch entities as expected. Hope this helps :)