How to Use the Serializer

How to Use the Serializer

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.

Activating the Serializer

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

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    # config/packages/framework.yaml
    framework:
        # ...
        serializer: { enable_annotations: true }
        # Alternatively, if you don't want to use annotations
        #serializer: { enabled: true }
    
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    <!-- config/packages/framework.xml -->
    <?xml version="1.0" encoding="UTF-8"?>
    <container xmlns="http://symfony.com/schema/dic/services"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:framework="http://symfony.com/schema/dic/symfony"
        xsi:schemaLocation="http://symfony.com/schema/dic/services
            http://symfony.com/schema/dic/services/services-1.0.xsd
            http://symfony.com/schema/dic/symfony
            http://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
        <framework:config>
            <!-- ... -->
            <framework:serializer enable-annotations="true" />
            <!--
            Alternatively, if you don't want to use annotations
            <framework:serializer enabled="true" />
            -->
        </framework:config>
    </container>
    
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    // config/packages/framework.php
    $container->loadFromExtension('framework', array(
        // ...
        'serializer' => array(
            'enable_annotations' => true,
            // Alternatively, if you don't want to use annotations
            //'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/Controller/DefaultController.php
namespace App\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 and will be loaded with four encoders (JsonEncoder, XmlEncoder, YamlEncoder, and CsvEncoder) and the ObjectNormalizer normalizer.

You can load normalizers and/or encoders 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.

Here is an example on how to load the GetSetMethodNormalizer:

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    # config/services.yaml
    services:
        get_set_method_normalizer:
            class: Symfony\Component\Serializer\Normalizer\GetSetMethodNormalizer
            public: false
            tags: [serializer.normalizer]
    
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    <!-- config/services.xml -->
    <?xml version="1.0" encoding="UTF-8"?>
    <container xmlns="http://symfony.com/schema/dic/services"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://symfony.com/schema/dic/services
            http://symfony.com/schema/dic/services/services-1.0.xsd">
    
        <services>
            <service id="get_set_method_normalizer" class="Symfony\Component\Serializer\Normalizer\GetSetMethodNormalizer" public="false">
                <tag name="serializer.normalizer" />
            </service>
        </services>
    </container>
    
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    // config/services.php
    use Symfony\Component\Serializer\Normalizer\GetSetMethodNormalizer;
    
    $container->register('get_set_method_normalizer', GetSetMethodNormalizer::class)
        ->setPublic(false)
        ->addTag('serializer.normalizer')
    ;
    

Using Serialization Groups Annotations

Enable serialization groups annotation with the following configuration:

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    # config/packages/framework.yaml
    framework:
        # ...
        serializer:
            enable_annotations: true
    
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    <!-- config/packages/framework.xml -->
    <?xml version="1.0" encoding="UTF-8"?>
    <container xmlns="http://symfony.com/schema/dic/services"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:framework="http://symfony.com/schema/dic/symfony"
        xsi:schemaLocation="http://symfony.com/schema/dic/services
            http://symfony.com/schema/dic/services/services-1.0.xsd
            http://symfony.com/schema/dic/symfony
            http://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
    
        <framework:config>
            <!-- ... -->
            <framework:serializer enable-annotations="true" />
        </framework:config>
    </container>
    
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    // config/packages/framework.php
    $container->loadFromExtension('framework', array(
        // ...
        'serializer' => array(
            'enable_annotations' => true,
        ),
    ));
    

Next, add the @Groups annotations to your class and choose which groups to use when serializing:

$json = $serializer->serialize(
    $someObject,
    'json', array('groups' => array('group1'))
);

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. Any service implementing the Doctrine\Common\Cache\Cache interface can be used.

A service leveraging APCu (and APC for PHP < 5.5) is built-in.

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    # config/packages/prod/framework.yaml
    framework:
        # ...
        serializer:
            cache: serializer.mapping.cache.apc
    
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    <!-- config/packages/prod/framework.xml -->
    <?xml version="1.0" encoding="UTF-8"?>
    <container xmlns="http://symfony.com/schema/dic/services"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:framework="http://symfony.com/schema/dic/symfony"
        xsi:schemaLocation="http://symfony.com/schema/dic/services
            http://symfony.com/schema/dic/services/services-1.0.xsd
            http://symfony.com/schema/dic/symfony
            http://symfony.com/schema/dic/symfony/symfony-1.0.xsd">
    
        <framework:config>
            <!-- ... -->
            <framework:serializer cache="serializer.mapping.cache.apc" />
        </framework:config>
    </container>
    
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    // config/packages/prod/framework.php
    $container->loadFromExtension('framework', array(
        // ...
        'serializer' => array(
            'cache' => 'serializer.mapping.cache.apc',
        ),
    ));
    

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
    $container->loadFromExtension('framework', array(
        // ...
        'serializer' => array(
            '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.