Callback on serializer Symfony - php

Question

I'm running Symfony 2.7 and I'm trying output an object (Doctrine entity) as JSON.
When I'm normalizing the object I want to convert some of it's values. To do this I found the "setCallbacks" method in the documentation but I'm kinda stumped on how to apply it to my case.
Is there any way to call the "setCallbacks" method on the normalizer that is set when calling Symfonys serializer service?
Here is a short example of what I'm trying to achieve:
//ExampleController.php
public function getJSONOrderByIdAction($id) {
$serializer = $this->get('serializer');
$normalizer = $serializer->getNormalizer(); // <- This is what I'm unable to do
$dateTimeToString = function ($dateTime) {
return $dateTime instanceof \DateTime ? $dateTime->format(\DateTime::ISO8601) : '';
};
$normalizer->setCallbacks(['time' => $dateTimeToString]);
$order = $this->getDoctrine()->find("AppBundle:Order", $id);
return new JsonResponse(["order" => $serializer->normalize($order, null, ["groups" => ["public"]])]);
}
I'm aware that most people have switched to the JMS serializer. It just seems as if the built in serializer should be able to handle what I'm trying to achieve.

Answer 1

The default Serializer service is created during dependency injection phase, and the Serializer interface do not allow editing of (full) retrieval of normalizers.
I think you have (at least) three choice here:
add your custom normalizer to the default Serializer service
add NormalizableInterface to your entities
create a new Serializer service (or a local object as suggested by the docs) as you were trying to do.
I think in your scenario, case 1 is preferred (since 2 becomes boring pretty fast).
I would do something like this; first create a custom Normalizer
<?php
namespace AppBundle;
class DateTimeNormalizer extends SerializerAwareNormalizer implements NormalizerInterface, DenormalizerInterface
{
/**
* {#inheritdoc}
*/
public function normalize($object, $format = null, array $context = array())
{
return $object->format(\DateTime::ISO8601);
}
/**
* {#inheritdoc}
*/
public function denormalize($data, $class, $format = null, array $context = array())
{
return new $class($data);
}
/**
* Checks if the given class is a DateTime.
*
* #param mixed $data Data to normalize.
* #param string $format The format being (de-)serialized from or into.
*
* #return bool
*/
public function supportsNormalization($data, $format = null)
{
return $data instanceof \DateTime;
}
/**
* Checks if the given class is a DateTime.
*
* #param mixed $data Data to denormalize from.
* #param string $type The class to which the data should be denormalized.
* #param string $format The format being deserialized from.
*
* #return bool
*/
public function supportsDenormalization($data, $type, $format = null)
{
$class = new \ReflectionClass($type);
return $class->isSubclassOf('\DateTime');
}
}
Then register it to your services:
# app/config/services.yml
services:
datetime_normalizer:
class: AppBundle\DateTimeNormalizer
tags:
- { name: serializer.normalizer }

Answer 2

My own solution
Following the advice from giosh94mhz I tried switching to JMS Serializer but ended up going back to Symfonys serializer.
JMS Serializer presented it's own issues and while searching for answers for those I stumbled upon a blog post by Thomas Jarrand that did an excellent job explaining how to make and implement your own normalizers in Symfony.

Answer 3

You can use callback normalizer of K. Dunglas component.
You can see that in ObjectNormalizer (in normalize method)
if (isset($this->callbacks[$attribute])) {
$attributeValue = call_user_func($this->callbacks[$attribute], $attributeValue);
}
This mean that you must use in callback array key the name of property you wan't to normalize.
For example in my entity I have field named "name" of type "pgarray" (like array for postgresql). I wan't to normalize this data. Instead array I want a string.
/**
* $object represent the property "name" because callback is attached to name property (setCallback)
*/
$nameCallback = function ($object, $outerObject = null) {
return $object[0];
};
$this->normalizer->setCallbacks(['name' => $dateCallback]);
Just remember since Symfony 4.2 you must use $context in DI to use callback.

Answer 4

In my opinion, you seem to be trying to over-complicate things. Here's the approach I've taken when I needed to serialize my entities as JSON:
PHP 2.5 and above allows you to implement the jsonSerialize method on your objects and just call json_encode directly on your object.
If you are still using PHP 2.4, you just need to manually call jsonSerialize() on your objects.
For example:
/**
* #ORM\Entity
*/
class MyEntity {
...
public function jsonSerialize() {
$data = array("foo" => $this->bar());
// add other data here ...
return $data
}
}
And then in calling code:
// for PHP 2.5 and up:
$normalized = json_encode($myEntityInstance);
// for PHP 2.4 and below
$normalized = json_encode($myEntityInstance->jsonSerialize());