How to Use the Serializer
Symfony provides a serializer to serialize/deserialize to and from objects and different formats (e.g. JSON or XML). Before using it, read the Serializer component docs to get familiar with its philosophy and the normalizers and encoders terminology.
Installation
In applications using Symfony Flex, run this command to
install the serializer
Symfony pack before using it:
1
$ 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:
1 2 3 4 5 6 7 8 9 10 11 12 13 14
// src/Controller/DefaultController.php
namespace App\Controller;
use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Serializer\SerializerInterface;
class DefaultController extends AbstractController
{
public function index(SerializerInterface $serializer): Response
{
// keep reading for usage examples
}
}
Or you can use the serialize
Twig filter in a template:
1
{{ 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
- XML: XmlEncoder
- CSV: CsvEncoder
- YAML: YamlEncoder
As well as the following normalizers:
- ObjectNormalizer
- DateTimeNormalizer
- DateTimeZoneNormalizer
- DateIntervalNormalizer
- FormErrorNormalizer
- DataUriNormalizer
- JsonSerializableNormalizer
- ArrayDenormalizer
- ConstraintViolationListNormalizer
- ProblemNormalizer
- BackedEnumNormalizer
- TranslatableNormalizer
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.
Danger
Always make sure to load the DateTimeNormalizer
when serializing the
DateTime
or DateTimeImmutable
classes to avoid excessive memory
usage and exposing internal details.
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; - AbstractObjectNormalizer
uses
preserve_empty_objects
to represent empty objects as{}
instead of[]
in JSON. - Serializer
uses
empty_array_as_object
to represent empty arrays as{}
instead of[]
in JSON.
You can pass the context as follows:
1 2 3 4 5 6 7
$serializer->serialize($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:
1 2 3 4 5 6 7
# config/packages/framework.yaml
framework:
# ...
serializer:
default_context:
enable_max_depth: true
yaml_indentation: 2
You can also specify the context on a per-property basis:
1 2 3 4 5 6 7 8 9 10 11 12
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 \DateTimeInterface $createdAt;
// ...
}
Use the options to specify context specific to normalization or denormalization:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
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 => '!Y-m-d'], // To prevent to have the time from the moment of denormalization
)]
public \DateTimeInterface $createdAt;
// ...
}
You can also restrict the usage of a context to some groups:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
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 \DateTimeInterface $createdAt;
// ...
}
The attribute 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.
If you repeat the same context in multiple properties, consider using the
#[Context]
attribute on your class to apply that context configuration to
all the properties of the class:
1 2 3 4 5 6 7 8 9 10 11 12 13 14
namespace App\Model;
use Symfony\Component\Serializer\Annotation\Context;
use Symfony\Component\Serializer\Normalizer\DateTimeNormalizer;
#[Context([DateTimeNormalizer::FORMAT_KEY => \DateTime::RFC3339])]
#[Context(
context: [DateTimeNormalizer::FORMAT_KEY => \DateTime::RFC3339_EXTENDED],
groups: ['extended'],
)]
class Person
{
// ...
}
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:
1 2 3 4
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:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
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 properties:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
// 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 int $id;
#[ORM\Column(type: 'string', length: 255)]
#[Groups(['show_product', 'list_product'])]
private string $name;
#[ORM\Column(type: 'text')]
#[Groups(['show_product'])]
private string $description;
}
You can also use the #[Groups]
attribute on class level:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
#[ORM\Entity]
#[Groups(['show_product'])]
class Product
{
#[ORM\Id]
#[ORM\GeneratedValue]
#[ORM\Column(type: 'integer')]
#[Groups(['list_product'])]
private int $id;
#[ORM\Column(type: 'string', length: 255)]
#[Groups(['list_product'])]
private string $name;
#[ORM\Column(type: 'text')]
private string $description;
}
In this example, the id
and the name
properties belong to the
show_product
and list_product
groups. The description
property
only belongs to the show_product
group.
Now that your groups are defined, you can choose which groups to use when serializing:
1 2 3 4 5 6 7
use Symfony\Component\Serializer\Context\Normalizer\ObjectNormalizerContextBuilder;
$context = (new ObjectNormalizerContextBuilder())
->withGroups('show_product')
->toArray();
$json = $serializer->serialize($product, 'json', $context);
Tip
The value of the groups
key can be a single string, or an array of strings.
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 theconfig/serializer/
directory. - The
serialization.yaml
orserialization.xml
file in theResources/config/
directory of a bundle; - All
*.yaml
and*.xml
files in theResources/config/serialization/
directory of a bundle.
Using Nested Attributes
To map nested properties, use the SerializedPath
configuration to define
their paths using a valid PropertyAccess syntax:
1 2 3 4 5 6 7 8 9 10 11
namespace App\Model;
use Symfony\Component\Serializer\Attribute\SerializedPath;
class Person
{
#[SerializedPath('[profile][information][birthday]')]
private string $birthday;
// ...
}
Using the configuration from above, denormalizing with a metadata-aware
normalizer will write the birthday
field from $data
onto the Person
object:
1 2 3 4 5 6 7 8 9
$data = [
'profile' => [
'information' => [
'birthday' => '01-01-1970',
],
],
];
$person = $normalizer->denormalize($data, Person::class, 'any');
$person->getBirthday(); // 01-01-1970
When using 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:
1 2 3 4 5
# config/packages/framework.yaml
framework:
# ...
serializer:
name_converter: 'serializer.name_converter.camel_case_to_snake_case'
Debugging the Serializer
Use the debug:serializer
command to dump the serializer metadata of a
given class:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
$ php bin/console debug:serializer 'App\Entity\Book'
App\Entity\Book
---------------
+----------+------------------------------------------------------------+
| Property | Options |
+----------+------------------------------------------------------------+
| name | [ |
| | "groups" => [ |
| | "book:read", |
| | "book:write", |
| | ], |
| | "maxDepth" => 1, |
| | "serializedName" => "book_name", |
| | "serializedPath" => null, |
| | "ignore" => false, |
| | "normalizationContexts" => [], |
| | "denormalizationContexts" => [] |
| | ] |
| isbn | [ |
| | "groups" => [ |
| | "book:read", |
| | ], |
| | "maxDepth" => null, |
| | "serializedName" => null, |
| | "serializedPath" => [data][isbn], |
| | "ignore" => false, |
| | "normalizationContexts" => [], |
| | "denormalizationContexts" => [] |
| | ] |
+----------+------------------------------------------------------------+
Going Further with the Serializer
API Platform provides an API system supporting the following formats:
- JSON-LD along with the Hydra Core Vocabulary
- OpenAPI v2 (formerly Swagger) and v3
- GraphQL
- JSON:API
- HAL
- JSON
- XML
- YAML
- 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.