How to Use the Serializer

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Read the updated version of this page for Symfony 7.2 (the current stable version).

Serializing and deserializing to and from objects and different formats (e.g. JSON or XML) is a very complex topic. Symfony comes with a Serializer Component, which gives you some tools that you can leverage for your solution.

In fact, before you start, get familiar with the serializer, normalizers and encoders by reading the Serializer Component documentation.

Activating the Serializer

The serializer service is not available by default. To turn it on, activate it in your configuration:

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# app/config/config.yml
framework:
    # ...
    serializer: { enable_annotations: true }
    # Alternatively, if you don't want to use annotations
    #serializer: { enabled: true }

Using the Serializer Service

Once enabled, the serializer service can be injected in any service where you need it or it can be used in a controller:

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// src/AppBundle/Controller/DefaultController.php
namespace AppBundle\Controller;

use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Symfony\Component\Serializer\SerializerInterface;

class DefaultController extends Controller
{
    public function indexAction(SerializerInterface $serializer)
    {
        // keep reading for usage examples
    }
}

Adding Normalizers and Encoders

Once enabled, the serializer service will be available in the container. It comes with a set of useful encoders and normalizers.

Encoders supporting the following formats are enabled:

As well as the following normalizers:

Custom normalizers and/or encoders can also be loaded by tagging them as serializer.normalizer and serializer.encoder. It's also possible to set the priority of the tag in order to decide the matching order.

Caution

Always make sure to load the DateTimeNormalizer when serializing the DateTime or DateTimeImmutable classes to avoid excessive memory usage and exposing internal details.

Here is an example on how to load the GetSetMethodNormalizer, a faster alternative to the `ObjectNormalizer` when data objects always use getters (getXxx()), issers (isXxx()) or hassers (hasXxx()) to read properties and setters (setXxx()) to change properties:

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# app/config/services.yml
services:
    get_set_method_normalizer:
        class: Symfony\Component\Serializer\Normalizer\GetSetMethodNormalizer
        public: false
        tags: [serializer.normalizer]

3.4

Support for hasser methods (hasXxx()) in GetSetMethodNormalizer was introduced in Symfony 3.4. In previous Symfony versions only getters (getXxx()) and issers (isXxx()) were supported.

Using Serialization Groups Annotations

Enable serialization groups annotation with the following configuration:

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# app/config/config.yml
framework:
    # ...
    serializer:
        enable_annotations: true

Next, add the @Groups annotations to your class:

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// src/Entity/Product.php
namespace App\Entity;

use Doctrine\ORM\Mapping as ORM;
use Symfony\Component\Serializer\Annotation\Groups;

/**
 * @ORM\Entity()
 */
class Product
{
    /**
     * @ORM\Id
     * @ORM\GeneratedValue
     * @ORM\Column(type="integer")
     * @Groups({"show_product", "list_product"})
     */
    private $id;

    /**
     * @ORM\Column(type="string", length=255)
     * @Groups({"show_product", "list_product"})
     */
    private $name;

    /**
     * @ORM\Column(type="integer")
     * @Groups({"show_product"})
     */
    private $description;
}

You can now choose which groups to use when serializing:

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$json = $serializer->serialize(
    $product,
    'json',
    ['groups' => 'show_product']
);

In addition to the @Groups annotation, the Serializer component also supports Yaml or XML files. These files are automatically loaded when being stored in one of the following locations:

  • The serialization.yml or serialization.xml file in the Resources/config/ directory of a bundle;
  • All *.yml and *.xml files in the Resources/config/serialization/ directory of a bundle.

Enabling the Metadata Cache

Metadata used by the Serializer component such as groups can be cached to enhance application performance. By default, the serializer uses the cache.system cache pool which is configured using the cache.system option.

Enabling a Name Converter

The use of a name converter service can be defined in the configuration using the name_converter option.

The built-in CamelCase to snake_case name converter can be enabled by using the serializer.name_converter.camel_case_to_snake_case value:

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# app/config/config.yml
framework:
    # ...
    serializer:
        name_converter: 'serializer.name_converter.camel_case_to_snake_case'

Going Further with the Serializer

ApiPlatform provides an API system supporting JSON-LD and Hydra Core Vocabulary hypermedia formats. It is built on top of the Symfony Framework and its Serializer component. It provides custom normalizers and a custom encoder, custom metadata and a caching system.

If you want to leverage the full power of the Symfony Serializer component, take a look at how this bundle works.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.
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