How to Use the Serializer ¶

Installation ¶

In applications using Symfony Flex, run this command to install the serializer Symfony pack before using it:

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$ composer require symfony/serializer-pack

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/Controller/DefaultController.php
namespace App\Controller;

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

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

Or you can use the serialize Twig filter in a template:

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{{ object|serialize(format = 'json') }}

See the twig reference for more information.

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:

• JSON: JsonEncoder
  JSON: JsonEncoder
• XML: XmlEncoder
  XML: XmlEncoder
• CSV: CsvEncoder
  CSV: CsvEncoder
• YAML: YamlEncoder
  YAML: YamlEncoder

As well as the following normalizers:

• ObjectNormalizer
  オブジェクトノーマライザー
• DateTimeNormalizer
  DateTimeNormalizer
• DateTimeZoneNormalizer
  DateTimeZoneNormalizer
• DateIntervalNormalizer
  DateIntervalNormalizer
• FormErrorNormalizer
  FormErrorノーマライザー
• DataUriNormalizer
  DataUriNormalizer
• JsonSerializableNormalizer
  JsonSerializableNormalizer
• ArrayDenormalizer
  ArrayDenormalizer
• ConstraintViolationListNormalizer
  ConstraintViolationListNormalizer
• ProblemNormalizer
  問題ノーマライザー
• BackedEnumNormalizer
  BackedEnumNormalizer

Other built-in normalizers and 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.

Serializer Context ¶

The serializer can define a context to control the (de)serialization of resources. This context is passed to all normalizers. For example:

• DateTimeNormalizer uses datetime_format key as date time format;
  DateTimeNormalizer は datetime_format キーを日時形式として使用します。
• AbstractObjectNormalizer uses preserve_empty_objects to represent empty objects as {} instead of [] in JSON.
  AbstractObjectNormalizer は、preserve_empty_objects を使用して、空のオブジェクトを JSON の [] ではなく {} として表します。
• Serializer uses empty_array_as_object to represent empty arrays as {} instead of [] in JSON.
  シリアライザは、空の配列を JSON の [] ではなく {} として表すために empty_array_as_object を使用します。

You can pass the context as follows:

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$serializer->serialize($something, 'json', [
    DateTimeNormalizer::FORMAT_KEY => 'Y-m-d H:i:s',
]);

$serializer->deserialize($someJson, Something::class, 'json', [
    DateTimeNormalizer::FORMAT_KEY => 'Y-m-d H:i:s',
]);

You can also configure the default context through the framework configuration:

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# config/packages/framework.yaml
framework:
    # ...
    serializer:
        default_context:
            enable_max_depth: true
            yaml_indentation: 2

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<!-- config/packages/framework.xml -->
<framework:config>
    <!-- ... -->
    <framework:serializer>
        <default-context enable-max-depth="true" yaml-indentation="2"/>
    </framework:serializer>
</framework:config>

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// config/packages/framework.php
use Symfony\Config\FrameworkConfig;
use Symfony\Component\Serializer\Normalizer\AbstractObjectNormalizer;
use Symfony\Component\Serializer\Encoder\YamlEncoder;

return static function (FrameworkConfig $framework) {
    $framework->serializer()
        ->defaultContext([
            AbstractObjectNormalizer::ENABLE_MAX_DEPTH => true,
            YamlEncoder::YAML_INDENTATION => 2,
        ])
    ;
};

You can also specify the context on a per-property basis:

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namespace App\Model;

use Symfony\Component\Serializer\Annotation\Context;
use Symfony\Component\Serializer\Normalizer\DateTimeNormalizer;

class Person
{
    /**
     * @Context({ DateTimeNormalizer::FORMAT_KEY = 'Y-m-d' })
     */
    public $createdAt;

    // ...
}

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namespace App\Model;

use Symfony\Component\Serializer\Annotation\Context;
use Symfony\Component\Serializer\Normalizer\DateTimeNormalizer;

class Person
{
    #[Context([DateTimeNormalizer::FORMAT_KEY => 'Y-m-d'])]
    public $createdAt;

    // ...
}

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App\Model\Person:
    attributes:
        createdAt:
            context:
                datetime_format: 'Y-m-d'

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<?xml version="1.0" encoding="UTF-8" ?>
<serializer xmlns="http://symfony.com/schema/dic/serializer-mapping"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/serializer-mapping
        https://symfony.com/schema/dic/serializer-mapping/serializer-mapping-1.0.xsd"
>
    <class name="App\Model\Person">
        <attribute name="createdAt">
            <context>
                <entry name="datetime_format">Y-m-d</entry>
            </context>
        </attribute>
    </class>
</serializer>

Use the options to specify context specific to normalization or denormalization:

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namespace App\Model;

use Symfony\Component\Serializer\Annotation\Context;
use Symfony\Component\Serializer\Normalizer\DateTimeNormalizer;

class Person
{
    #[Context(
        normalizationContext: [DateTimeNormalizer::FORMAT_KEY => 'Y-m-d'],
        denormalizationContext: [DateTimeNormalizer::FORMAT_KEY => \DateTime::RFC3339],
    )]
    public $createdAt;

    // ...
}

You can also restrict the usage of a context to some groups:

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namespace App\Model;

use Symfony\Component\Serializer\Annotation\Context;
use Symfony\Component\Serializer\Annotation\Groups;
use Symfony\Component\Serializer\Normalizer\DateTimeNormalizer;

class Person
{
    #[Groups(['extended'])]
    #[Context([DateTimeNormalizer::FORMAT_KEY => \DateTime::RFC3339])]
    #[Context(
        context: [DateTimeNormalizer::FORMAT_KEY => \DateTime::RFC3339_EXTENDED],
        groups: ['extended'],
    )]
    public $createdAt;

    // ...
}

The attribute/annotation can be repeated as much as needed on a single property. Context without group is always applied first. Then context for the matching groups are merged in the provided order.

Using Context Builders ¶

To define the (de)serialization context, you can use "context builders", which are objects that help you to create that context by providing autocompletion, validation, and documentation:

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use Symfony\Component\Serializer\Context\Normalizer\DateTimeNormalizerContextBuilder;

$contextBuilder = (new DateTimeNormalizerContextBuilder())->withFormat('Y-m-d H:i:s');
$serializer->serialize($something, 'json', $contextBuilder->toArray());

Each normalizer/encoder has its related context builder. To create a more complex (de)serialization context, you can chain them using the withContext() method:

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use Symfony\Component\Serializer\Context\Encoder\CsvEncoderContextBuilder;
use Symfony\Component\Serializer\Context\Normalizer\ObjectNormalizerContextBuilder;

$initialContext = [
    'custom_key' => 'custom_value',
];

$contextBuilder = (new ObjectNormalizerContextBuilder())
    ->withContext($initialContext)
    ->withGroups(['group1', 'group2']);

$contextBuilder = (new CsvEncoderContextBuilder())
    ->withContext($contextBuilder)
    ->withDelimiter(';');

$serializer->serialize($something, 'csv', $contextBuilder->toArray());

You can also create your context builders to have autocompletion, validation, and documentation for your custom context values.

Using Serialization Groups Attributes ¶

You can add #[Groups] attributes 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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use Symfony\Component\Serializer\Context\Normalizer\ObjectNormalizerContextBuilder;

$context = (new ObjectNormalizerContextBuilder())
    ->withGroups('show_product')
    ->toArray();

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

In addition to the #[Groups] attribute, the Serializer component also supports YAML or XML files. These files are automatically loaded when being stored in one of the following locations:

• All *.yaml and *.xml files in the config/serializer/ directory.
  config/serializer/directory 内のすべての *.yaml および *.xml ファイル。
• The serialization.yaml or serialization.xml file in the Resources/config/ directory of a bundle;
  バンドルの Resources/config/ ディレクトリにある serialization.yaml または serialization.xml ファイル。
• All *.yaml and *.xml files in the Resources/config/serialization/ directory of a bundle.
  バンドルの Resources/config/serialization/directory 内のすべての *.yaml および *.xml ファイル。

Using Nested Attributes ¶

To map nested properties, use the SerializedPath configuration to define their paths using a valid PropertyAccess syntax:

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namespace App\Model;

use Symfony\Component\Serializer\Annotation\SerializedPath;

class Person
{
    /**
     * @SerializedPath("[profile][information][birthday]")
     */
    private string $birthday;

    // ...
}

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namespace App\Model;

use Symfony\Component\Serializer\Annotation\SerializedPath;

class Person
{
    #[SerializedPath('[profile][information][birthday]')]
    private string $birthday;

    // ...
}

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App\Model\Person:
    attributes:
        dob:
            serialized_path: '[profile][information][birthday]'

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<?xml version="1.0" encoding="UTF-8" ?>
<serializer xmlns="http://symfony.com/schema/dic/serializer-mapping"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/serializer-mapping
        https://symfony.com/schema/dic/serializer-mapping/serializer-mapping-1.0.xsd"
>
    <class name="App\Model\Person">
        <attribute name="dob" serialized-path="[profile][information][birthday]"/>
    </class>
</serializer>

Using the configuration from above, denormalizing with a metadata-aware
normalizer will write the birthday field from $data onto the Person
object:

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$data = [
    'profile' => [
        'information' => [
            'birthday' => '01-01-1970',
        ],
    ],
];
$person = $normalizer->denormalize($data, Person::class, 'any'); 
$person->getBirthday(); // 01-01-1970

When using annotations or attributes, the SerializedPath can either
be set on the property or the associated _getter_ method. The SerializedPath cannot be used in combination with a SerializedName for the same property.

Configuring the Metadata Cache ¶

The metadata for the serializer is automatically 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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# config/packages/framework.yaml
framework:
    # ...
    serializer:
        name_converter: 'serializer.name_converter.camel_case_to_snake_case'

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<!-- config/packages/framework.xml -->
<framework:config>
    <!-- ... -->
    <framework:serializer name-converter="serializer.name_converter.camel_case_to_snake_case"/>
</framework:config>

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// config/packages/framework.php
use Symfony\Config\FrameworkConfig;

return static function (FrameworkConfig $framework) {
    $framework->serializer()->nameConverter('serializer.name_converter.camel_case_to_snake_case');
};

Going Further with the Serializer ¶

API Platform provides an API system supporting the following formats:

• JSON-LD along with the Hydra Core Vocabulary
  JSON-LD と Hydra Core ボキャブラリ
• OpenAPI v2 (formerly Swagger) and v3
  OpenAPI v2 (以前の Swagger) および v3
• GraphQL
  GraphQL
• JSON:API
  JSON:API
• HAL
  ハル
• JSON
  JSON
• XML
  XML
• YAML
  YAML
• CSV
  CSV

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.