Denormalize nested structure in objects with Symfony 2 serializer

Question

I'm working on a Symfony 2 project with version 2.8 and I'm using the build-in component Serializer -> http://symfony.com/doc/current/components/serializer.html

I have a JSON structure provided by a web service. After deserialization, I want to denormalize my content in objects. Here is my structure (model/make in a car application context).

[{
"0": {
    "id": 0,
    "code": 1,
    "model": "modelA",
    "make": {
        "id": 0,
        "code": 1,
        "name": "makeA"
    }
  }
} , {
 "1": {
    "id": 1,
    "code": 2,
    "model": "modelB",
    "make": {
        "id": 0,
        "code": 1,
        "name": "makeA"
    }
  }
}]

My idea is to populate a VehicleModel object which contains a reference to a VehicleMake object.

class VehicleModel {
    public $id;
    public $code;
    public $model;
    public $make; // VehicleMake
}

Here is what I do:

// Retrieve data in JSON
$data = ...
$serializer = new Serializer([new ObjectNormalizer(), new ArrayDenormalizer()], [new JsonEncoder()]);
$models = $serializer->deserialize($data, '\Namespace\VehicleModel[]', 'json');

In result, my object VehicleModel is correctly populated but $make is logically a key/value array. Here I want a VehicleMake instead.

Is there a way to do that?

Answer 1

The ObjectNormalizer needs more configuration. You will at least need to supply the fourth parameter of type PropertyTypeExtractorInterface.

Here's a (rather hacky) example:

<?php
use Symfony\Component\PropertyInfo\PropertyTypeExtractorInterface;
use Symfony\Component\PropertyInfo\Type;
use Symfony\Component\Serializer\Encoder\JsonEncoder;
use Symfony\Component\Serializer\Normalizer\ArrayDenormalizer;
use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
use Symfony\Component\Serializer\Serializer;

$a = new VehicleModel();
$a->id = 0;
$a->code = 1;
$a->model = 'modalA';
$a->make = new VehicleMake();
$a->make->id = 0;
$a->make->code = 1;
$a->make->name = 'makeA';

$b = new VehicleModel();
$b->id = 1;
$b->code = 2;
$b->model = 'modelB';
$b->make = new VehicleMake();
$b->make->id = 0;
$b->make->code = 1;
$b->make->name = 'makeA';

$data = [$a, $b];

$serializer = new Serializer(
    [new ObjectNormalizer(null, null, null, new class implements PropertyTypeExtractorInterface {
        /**
         * {@inheritdoc}
         */
        public function getTypes($class, $property, array $context = array())
        {
            if (!is_a($class, VehicleModel::class, true)) {
                return null;
            }

            if ('make' !== $property) {
                return null;
            }

            return [
                new Type(Type::BUILTIN_TYPE_OBJECT, true, VehicleMake::class)
            ];
        }
    }), new ArrayDenormalizer()],
    [new JsonEncoder()]
);

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

$models = $serializer->deserialize($json, VehicleModel::class . '[]', 'json');
print_r($models);

---

Note that in your example json, the first entry has an array as value for make. I took this to be a typo, if it's deliberate, please leave a comment.

To make this more automatic you might want to experiment with the PhpDocExtractor.

Answer 2

In cases when you need more flexibility in denormalization it's good to create your own denormalizers.

$serializer = new Serializer(
  [
    new ArrayNormalizer(), 
    new VehicleDenormalizer(), 
    new VehicleMakeDenormalizer()
  ], [
    new JsonEncoder()
  ]
);
$models = $serializer->deserialize(
  $data, 
  '\Namespace\VehicleModel[]', 
  'json'
);

Here the rough code of such denormalizer

class VehicleDenormalizer implements DenormalizerInterface, DenormalizerAwareInterface
    {
      public function denormalize($data, $class, $format, $context) 
      {
        $vehicle = new VehicleModel();
        ...
        $vehicleMake = $this->denormalizer->denormalize(
          $data->make,
          VehicleMake::class,
          $format,
          $context
        );
        $vehicle->setMake($vehicleMake);
        ...
      }
    }

I only have doubts on should we rely on $this->denormalizer->denormalize (which works properly just because we use Symfony\Component\Serializer\Serializer) or we must explicitly inject VehicleMakeDenormalizer into VehicleDenormalizer

$vehicleDenormalizer = new VehicleDenormalizer();
$vehicleDenormalizer->setVehicleMakeDenormalizer(new VehicleMakeDenormalizer());

Answer 3

The easiest way would be to use the ReflectionExtractor if your Vehicle class has some type hints.

class VehicleModel {
    public $id;
    public $code;
    public $model;
    /** @var VehicleMake */
    public $make;
}

You can pass the Symfony\Component\PropertyInfo\Extractor\ReflectionExtractor as argument to the ObjectNormalizer when you initialize the Serializer

$serializer = new Serializer([new ObjectNormalizer(null, null, null, new ReflectionExtractor()), new ArrayDenormalizer()], [new JsonEncoder()]);
$models = $serializer->deserialize($data, '\Namespace\VehicleModel[]', 'json');