Symfony - How to specify root to deserialize json array to object using JMS\Serializer

Question

I receive json responses from a certain server to API requests in this format:

{
  "data": {
    #result here
  }
}

But I need to do deserialization of the result itself inside "data". I could not find in the documentation how to specify the json deserialization root

Example:

# Json Response
{
  "data": {
    "totalCount": 3,
    "version": "v1"
  }
}

<?php
# The object to deserialize into
namespace App;

use JMS\Serializer\Annotation as Serializer;

class ExampleResponse
{
    /**
     * @var int
     *
     * @Serializer\Type("integer")
     * @Serializer\SerializedName("totalCount")
     */
    protected $totalCount;

    /**
     * @var string
     *
     * @Serializer\Type("string")
     * @Serializer\SerializedName("version")
     */
    protected $version;
}

# Deserialization call
# I have to decode the json into an array and then json encode the internals of "data"
$this->serializer->deserialize(
    json_encode(
        json_decode(
            $json,
            true,
            512,
            JSON_THROW_ON_ERROR
        )['data'],
        JSON_THROW_ON_ERROR
    ),
    App\ExampleResponse::class,
    'json'
)

Is there a better solution?

Answer 1

It is possible but a little bit cumbersome.

The easiest approach is to use json_decode and deserialize the object with the fromArray method:

$response = json_decode($json, true);
$this->serializer->fromArray($response['data'], App\ExampleResponse::class)

The other solution is to use a subscriber to listen on the pre_deserialize event:

class JsonDeserializationSubscriber implements EventSubscriberInterface
{
    public static function getSubscribedEvents(): array
    {
        return [[
            'event' => 'serializer.pre_deserialize',
            'method' => 'onPreDeSerialize',
            'format' => 'json', // optional format
            'priority' => 0, // optional priority
        ]];
    }


    public function onPreDeSerialize(PreDeserializeEvent $event): void
    {
        $data = $event->getData();

        if (is_array($data) && array_key_exists('data', $data)) {
            $event->setData($data['data']);
        }

    }

And you also need to configure the listener:

 $serializer = SerializerBuilder::create()->configureListeners(
   fn (EventDispatcher $e) => $e->addSubscriber(new JsonDeserializationSubscriber())
)->build();
$serializer->deserialize($json, App\ExampleResponse::class, 'json');