[ajax] How to encode Doctrine entities to JSON in Symfony 2.0 AJAX application?

I'm developing game app and using Symfony 2.0. I have many AJAX requests to the backend. And more responses is converting entity to JSON. For example:

class DefaultController extends Controller
{           
    public function launchAction()
    {   
        $user = $this->getDoctrine()
                     ->getRepository('UserBundle:User')                
                     ->find($id);

        // encode user to json format
        $userDataAsJson = $this->encodeUserDataToJson($user);
        return array(
            'userDataAsJson' => $userDataAsJson
        );            
    }

    private function encodeUserDataToJson(User $user)
    {
        $userData = array(
            'id' => $user->getId(),
            'profile' => array(
                'nickname' => $user->getProfile()->getNickname()
            )
        );

        $jsonEncoder = new JsonEncoder();        
        return $jsonEncoder->encode($userData, $format = 'json');
    }
}

And all my controllers do the same thing: get an entity and encode some of its fields to JSON. I know that I can use normalizers and encode all entitities. But what if an entity has cycled links to other entity? Or the entities graph is very big? Do you have any suggestions?

I think about some encoding schema for entities... or using NormalizableInterface to avoid cycling..,

I just had to solve the same problem: json-encoding an entity ("User") having a One-To-Many Bidirectional Association to another Entity ("Location").

I tried several things and I think now I found the best acceptable solution. The idea was to use the same code as written by David, but somehow intercept the infinite recursion by telling the Normalizer to stop at some point.

I did not want to implement a custom normalizer, as this GetSetMethodNormalizer is a nice approach in my opinion (based on reflection etc.). So I've decided to subclass it, which is not trivial at first sight, because the method to say if to include a property (isGetMethod) is private.

But, one could override the normalize method, so I intercepted at this point, by simply unsetting the property that references "Location" - so the inifinite loop is interrupted.

In code it looks like this:

class GetSetMethodNormalizer extends \Symfony\Component\Serializer\Normalizer\GetSetMethodNormalizer {

    public function normalize($object, $format = null)
    {
        // if the object is a User, unset location for normalization, without touching the original object
        if($object instanceof \Leonex\MoveBundle\Entity\User) {
            $object = clone $object;
            $object->setLocations(new \Doctrine\Common\Collections\ArrayCollection());
        }

        return parent::normalize($object, $format);
    }

} 

You can automatically encode into Json, your complex entity with:

use Symfony\Component\Serializer\Serializer;
use Symfony\Component\Serializer\Normalizer\GetSetMethodNormalizer;
use Symfony\Component\Serializer\Encoder\JsonEncoder;

$serializer = new Serializer(array(new GetSetMethodNormalizer()), array('json' => new 
JsonEncoder()));
$json = $serializer->serialize($entity, 'json');

If you are using Symfony 2.7 or above, and don't want to include any additional bundle for serializing, maybe you can follow this way to seialize doctrine entities to json -

1. In my (common, parent) controller, I have a function that prepares the serializer

   use Symfony\Component\Serializer\Encoder\JsonEncoder;
   use Symfony\Component\Serializer\Mapping\Factory\ClassMetadataFactory;
   use Symfony\Component\Serializer\Mapping\Loader\AnnotationLoader;
   use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
   use Symfony\Component\Serializer\Serializer;
   
   // -----------------------------
   
   /**
    * @return Serializer
    */
   protected function _getSerializer()
   {  
       $classMetadataFactory = new ClassMetadataFactory(new AnnotationLoader(new AnnotationReader()));
       $normalizer           = new ObjectNormalizer($classMetadataFactory);
   
       return new Serializer([$normalizer], [new JsonEncoder()]);
   }
   

2. Then use it to serialize Entities to JSON

   $this->_getSerializer()->normalize($anEntity, 'json');
   $this->_getSerializer()->normalize($arrayOfEntities, 'json');
   

Done!

But you may need some fine tuning. For example -

• If your entities have circular reference, check how to handle it.
• If you want to ignore some properties, can do it
• Even better, you can serialize only selective attributes.

I found the solution to the problem of serializing entities was as follows:

#config/config.yml

services:
    serializer.method:
        class: Symfony\Component\Serializer\Normalizer\GetSetMethodNormalizer
    serializer.encoder.json:
        class: Symfony\Component\Serializer\Encoder\JsonEncoder
    serializer:
        class: Symfony\Component\Serializer\Serializer
        arguments:
            - [@serializer.method]
            - {json: @serializer.encoder.json }

in my controller:

$serializer = $this->get('serializer');

$entity = $this->get('doctrine')
               ->getRepository('myBundle:Entity')
               ->findOneBy($params);


$collection = $this->get('doctrine')
               ->getRepository('myBundle:Entity')
               ->findBy($params);

$toEncode = array(
    'response' => array(
        'entity' => $serializer->normalize($entity),
        'entities' => $serializer->normalize($collection)
    ),
);

return new Response(json_encode($toEncode));

other example:

$serializer = $this->get('serializer');

$collection = $this->get('doctrine')
               ->getRepository('myBundle:Entity')
               ->findBy($params);

$json = $serializer->serialize($collection, 'json');

return new Response($json);

you can even configure it to deserialize arrays in http://api.symfony.com/2.0

To complete the answer: Symfony2 comes with a wrapper around json_encode: Symfony/Component/HttpFoundation/JsonResponse

Typical usage in your Controllers:

...
use Symfony\Component\HttpFoundation\JsonResponse;
...
public function acmeAction() {
...
return new JsonResponse($array);
}

When you need to create a lot of REST API endpoints on Symfony, the best way is to use following stack of bundles:

1. JMSSerializerBundle for the serialization of Doctrine entities
2. FOSRestBundle bundle for response view listener. Also it can generate definition of routes based on controller/action name.
3. NelmioApiDocBundle to auto-generate online documentation and Sandbox(which allows to test endpoint without any external tool).

When you configure everything properly, you entity code will look like:

use Doctrine\ORM\Mapping as ORM;
use JMS\Serializer\Annotation as JMS;

/**
 * @ORM\Table(name="company")
 */
class Company
{

    /**
     * @var string
     *
     * @ORM\Column(name="name", type="string", length=255)
     *
     * @JMS\Expose()
     * @JMS\SerializedName("name")
     * @JMS\Groups({"company_overview"})
     */
    private $name;

    /**
     * @var Campaign[]
     *
     * @ORM\OneToMany(targetEntity="Campaign", mappedBy="company")
     * 
     * @JMS\Expose()
     * @JMS\SerializedName("campaigns")
     * @JMS\Groups({"campaign_overview"})
     */
    private $campaigns;
}

Then, code in controller:

use Nelmio\ApiDocBundle\Annotation\ApiDoc;
use FOS\RestBundle\Controller\Annotations\View;

class CompanyController extends Controller
{

    /**
     * Retrieve all companies
     *
     * @View(serializerGroups={"company_overview"})
     * @ApiDoc()
     *
     * @return Company[]
     */
    public function cgetAction()
    {
        return $this->getDoctrine()->getRepository(Company::class)->findAll();
    }
}

The benefits of such set up are:

• @JMS\Expose() annotations in entity can be added to simple fields, and to any types of relations. Also there is possibility to expose result of some method execution (use annotation @JMS\VirtualProperty() for that)
• With serialization groups we can control exposed fields in different situations.
• Controllers are very simple. Action method can directly return an entity or array of entities, and they will be automatically serialized.
• And @ApiDoc() allows to test the endpoint directly from browser, without any REST client or JavaScript code

I had the same problem and I chosed to create my own encoder, which will cope by themself with recursion.

I created classes which implements Symfony\Component\Serializer\Normalizer\NormalizerInterface, and a service which holds every NormalizerInterface.

#This is the NormalizerService

class NormalizerService 
{

   //normalizer are stored in private properties
   private $entityOneNormalizer;
   private $entityTwoNormalizer;

   public function getEntityOneNormalizer()
   {
    //Normalizer are created only if needed
    if ($this->entityOneNormalizer == null)
        $this->entityOneNormalizer = new EntityOneNormalizer($this); //every normalizer keep a reference to this service

    return $this->entityOneNormalizer;
   }

   //create a function for each normalizer



  //the serializer service will also serialize the entities 
  //(i found it easier, but you don't really need it)
   public function serialize($objects, $format)
   {
     $serializer = new Serializer(
            array(
                $this->getEntityOneNormalizer(),
                $this->getEntityTwoNormalizer()
            ),
            array($format => $encoder) );

     return $serializer->serialize($response, $format);
}

An example of a Normalizer :

use Symfony\Component\Serializer\Normalizer\NormalizerInterface;

class PlaceNormalizer implements NormalizerInterface {

private $normalizerService;

public function __construct($normalizerService)
{
    $this->service = normalizerService;

}

public function normalize($object, $format = null) {
    $entityTwo = $object->getEntityTwo();
    $entityTwoNormalizer = $this->service->getEntityTwoNormalizer();

    return array(
        'param' => object->getParam(),
        //repeat for every parameter
        //!!!! this is where the entityOneNormalizer dealt with recursivity
        'entityTwo' => $entityTwoNormalizer->normalize($entityTwo, $format.'_without_any_entity_one') //the 'format' parameter is adapted for ignoring entity one - this may be done with different ways (a specific method, etc.)
    );
}

}

In a controller :

$normalizerService = $this->get('normalizer.service'); //you will have to configure services.yml
$json = $normalizerService->serialize($myobject, 'json');
return new Response($json);

The complete code is here : https://github.com/progracqteur/WikiPedale/tree/master/src/Progracqteur/WikipedaleBundle/Resources/Normalizer

in Symfony 2.3

/app/config/config.yml

framework:
    # ?????? ??????????????? ???????? ? ???????, json, xml ? ???????
    serializer:
        enabled: true

services:
    object_normalizer:
        class: Symfony\Component\Serializer\Normalizer\GetSetMethodNormalizer
        tags:
        # ???????? ? ???? ????????? ???? ??????, ??? ??. ?????, ?.?. ????? ???????? ?? ?????
          - { name: serializer.normalizer }

and example for your controller:

/**
 * ????? ???????? ?? ?? ??????? ? ?? ?????
 * @Route("/search/", name="orgunitSearch")
 */
public function orgunitSearchAction()
{
    $array = $this->get('request')->query->all();

    $entity = $this->getDoctrine()
        ->getRepository('IntranetOrgunitBundle:Orgunit')
        ->findOneBy($array);

    $serializer = $this->get('serializer');
    //$json = $serializer->serialize($entity, 'json');
    $array = $serializer->normalize($entity);

    return new JsonResponse( $array );
}

but the problems with the field type \DateTime will remain.

This is more an update (for Symfony v:2.7+ and JmsSerializer v:0.13.*@dev), so to avoid that Jms tries to load and serialise the whole object graph ( or in case of cyclic relation ..)

Model:

use Doctrine\ORM\Mapping as ORM;
use JMS\Serializer\Annotation\ExclusionPolicy;  
use JMS\Serializer\Annotation\Exclude;  
use JMS\Serializer\Annotation\MaxDepth; /* <=== Required */
/**
 * User
 *
 * @ORM\Table(name="user_table")
///////////////// OTHER Doctrine proprieties //////////////
 */
 public class User
{
    /**
     * @var integer
     *
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    protected   $id;

    /**
     * @ORM\ManyToOne(targetEntity="FooBundle\Entity\Game")
     * @ORM\JoinColumn(nullable=false)
     * @MaxDepth(1)
     */
    protected $game;
   /*
      Other proprieties ....and Getters ans setters
      ......................
      ......................
   */

Inside an Action:

use JMS\Serializer\SerializationContext;
  /* Necessary include to enbale max depth */

  $users = $this
              ->getDoctrine()
              ->getManager()
              ->getRepository("FooBundle:User")
              ->findAll();

  $serializer = $this->container->get('jms_serializer');
  $jsonContent = $serializer
                   ->serialize(
                        $users, 
                        'json', 
                        SerializationContext::create()
                                 ->enableMaxDepthChecks()
                  );

  return new Response($jsonContent);

With php5.4 now you can do :

use JsonSerializable;

/**
* @Entity(repositoryClass="App\Entity\User")
* @Table(name="user")
*/
class MyUserEntity implements JsonSerializable
{
    /** @Column(length=50) */
    private $name;

    /** @Column(length=50) */
    private $login;

    public function jsonSerialize()
    {
        return array(
            'name' => $this->name,
            'login'=> $this->login,
        );
    }
}

And then call

json_encode(MyUserEntity);

Now you can also use Doctrine ORM Transformations to convert entities to nested arrays of scalars and back