Serialization Event Subscriber

Hey Skander B.!

Excellent question :). First, when you serialize an object with the Symfony serializer, "basically" the fields that will be included are all the fields that have a getter method. If I remember correctly, with the paginator, you're dealing with a SlidingPagination instance (https://symfonycasts.com/screencast/api-platform) which extends AbstractPagination https://github.com/KnpLabs/knp-components/blob/master/src/Knp/Component/Pager/Pagination/AbstractPagination.php. As you can see - if you search for public function get, you'll find methods for the current page, the current items, total item count and a few others - but not links. My guess is that the fields you ARE seeing are these fields.

To improve this, you have a few options:

1) Create your own class that has all the "getter" methods you want for the fields and manually take the SlidingPagination object and populate your object with its data. Then serializer your object.

2) Create a custom serializer "normalizer". This is basically a class that will take complete control over the normalization process of just the SlidingPagination class and will give you control over including whatever fields you want. For example, here is a "core normalizer" whose job is to make sure that ConstraintViolationList objects (that's what Symfony's validator returns, and it includes validation errors) is normalized into a useful structure: https://github.com/symfony/symfony/blob/4.4/src/Symfony/Component/Serializer/Normalizer/ConstraintViolationListNormalizer.php

Cheers!

Thank you very much for your quick and detailed answer! :D I also had the idea to write my own normalizer for it.
And you are definitely right, I get a <u>SlidingPagination</u> object. I also suspected that "links" had no public getter. However, I really only get the current items, so by the <u><i>getItems()</i></u> method in <u>AbstractPagination</u> class, right?
All other getters are ignored. This includes for example <i><u>getTotalItemCount()</u></i>. I have noticed that in SlidingPagination the <i><u>getPaginationData()</u></i> method exposes all data that I am missing:

...
`
$viewData = [

        'last' => $pageCount,
        'current' => $current,
        'numItemsPerPage' => $this->numItemsPerPage,
        'first' => 1,
        'pageCount' => $pageCount,
        'totalCount' => $this->totalCount,
    ];

$viewData = array_merge($viewData, $this->paginatorOptions, $this->customParameters);

    if ($current - 1 > 0) {
        $viewData['previous'] = $current - 1;
    }

    if ($current + 1 <= $pageCount) {
        $viewData['next'] = $current + 1;
    }
    $viewData['pagesInRange'] = $pages;
    $viewData['firstPageInRange'] = min($pages);
    $viewData['lastPageInRange']  = max($pages);

    if ($this->getItems() !== null) {
        $viewData['currentItemCount'] = $this->count();
        $viewData['firstItemNumber'] = (($current - 1) * $this->numItemsPerPage) + 1;
        $viewData['lastItemNumber'] = $viewData['firstItemNumber'] + $viewData['currentItemCount'] - 1;
    }

    return $viewData;

`
I just wonder why of all methods only <i><u>getItems()</u></i> is captured by the symfony normalizer and other getters of <u>AbstractPagination</u> are not? Or have I looked at the wrong classes for this? It is generally difficult for me to debug during the serialization process. Do you have any tips?
Just for completion I'm attaching you an example json of a serialized <u>SlidingPagination</u> object:

`[

{
    "id": 2001,
    "name": "Kshlerin PLC",
    "website": "greenholt.biz",
    "phone": "12",
    "mobile": "(537) 548-0008 x879",
    "email": "Lavinia Carter"
},
{
    "id": 2002,
    "name": "Connelly-Gerhold",
    "website": "kreiger.org",
    "phone": "12",
    "mobile": "1-813-685-8416 x71342",
    "email": "Dr. Mekhi Willms II"
},
{
    "id": 2003,
    "name": "White-Corkery",
    "website": "bergstrom.com",
    "phone": "12",
    "mobile": "542.630.5984 x9532",
    "email": "Rogers Roob"
},
{
    "id": 2004,
    "name": "Heaney-Fay",
    "website": "purdy.com",
    "phone": "12",
    "mobile": "1-642-747-8689",
    "email": "Leta Bailey"
},
{
    "id": 2005,
    "name": "Abshire-Mosciski",
    "website": "turcotte.com",
    "phone": "12",
    "mobile": "1-662-999-6986 x832",
    "email": "Dixie Weber"
}

]`

Hey Skander B.!

Hmm. Indeed, this looks weird to me - I would expect all the getters to be called by default. But, it's even stranger than that. If this follows the normal normalization rules, then the "getItems()" method would cause an items key to be added in the JSON. But in your JSON example, all the results are at the root level, not under an "items" key. So, that's a mystery :).

It makes me wonder if the project already has a custom normalizer for this class. I could totally be wrong.. but I don't see any "core" normalizer for that pagination class that comes with KnpPaginator... so I don't think it's being added by that bundle. Your question on how to debug is an excellent one :). Unfortunately, there isn't a spot on the web debug toolbar/profiler for the serializer... which would be super handy. But, you can at least see what normalizers exist on your project by running:

php bin/console debug:container --tag=serializer.normalizer

I would check there to see if any of those classes might be responsible.

... Wait! I think I just figured it out! AbstractPagination implements Iterator. If there is no normalizer for a specific class that implements Iterator, then the Serializer automatically "loops over" the object and normalizes each item (https://github.com/symfony/symfony/blob/46e94d94255ea785f5b138312e6f664da2ccfbe9/src/Symfony/Component/Serializer/Serializer.php#L159). THAT is what explains the result :).

So, creating a custom normalizer is still a great option... and we can now explain what's going on ;).

Cheers!

Hi Pawel,

AFAIK, it isn't. Probably you don't see it in the docs for bundle, try to look at docs for serializer package itself:
https://jmsyst.com/libs/ser...

Cheers!

thanks, (sorry, somehow I forgot it's not about Symfony The Serializer Component, and I searched there)

Hey Tim,

Hm, could you tell us to what exactly are you trying to serialize JobOffer? Are you trying to serialize JobOffer as JSON? And your response looks like a var_dump()' output. What code gives you this output? And how did you expose Media entity properties? As I understand this entity comes from third-party bundle, so you can't add annotation to it, right? Do you use some YAML/XML configuration for it?

Cheers!

Hey Victor,

I'm trying to serialize my JobOffer Entity just like Programmer in the tutorial. This is in my showAction in my jobOfferController.php:

    /**
     * @Route("/api/joboffers/{id}", name="api_joboffer_show")
     * @Method("GET")
     */
    public function showAction($id)
    {
        /**
         * @var JobOffer $jobOffer
         */
        $jobOffer = $this->getDoctrine()
            ->getRepository('AppBundle:JobOffer\JobOffer')
            ->findOneById($id);

        if(!$jobOffer)
        {
            throw $this->createNotFoundException('No job Offer found with ID: ' . $id);
        }

        $response = $this->createApiResponse($jobOffer);

        return $response;
    }

The createApiResponse lives in my BaseController.php like in the tutorial:

class BaseController extends Controller
{
    protected function createApiResponse($data, $statusCode = 200)
    {
        $json = $this->serialize($data);

        return new Response($json, $statusCode, [
            'Content-Type' => 'application/json'
        ]);
    }

    protected function serialize($data)
    {
        $context = new SerializationContext();
        $context->setSerializeNull(true);

        $request = $this->get('request_stack')->getCurrentRequest();
        $groups = array("Default");

        if ($request->query->get('deep')){
            $groups[] = 'deep';
        }

        $context->setGroups($groups);

        return $this->container->get('jms_serializer')
            ->serialize($data, 'json', $context);
    }
}

For the image I use the Sonata Media Bundle (I have the same issue with the Sonata Classification Bundle)
And I use a media.yml to configure it (config.yml imports: - { resource: Sonata/media.yml }) sonata_madia: ...
Full configuration:
https://sonata-project.org/bundles/media/3-x/doc/reference/advanced_configuration.html

I hope this makes things more clear.

Hey Tim V.!

Ok, I might have some info for you, though I have almost zero experience with the Sonata libraries :).

1) SonataMediaBundle itself comes with some serialization config that tells JMSSerializer how to serialize the Media entity: https://github.com/sonata-project/SonataMediaBundle/blob/3.x/src/Resources/config/serializer/Model.Media.xml. That's great news! However, notice that every field is assigned a few groups like "sonata_api_read,sonata_api_write,sonata_search" for the "name" field. When you serialize, I believe you will need to include one of these groups so that these fields setup. I would add a new, optional 2nd $groups argument to the serialize() so that you can pass in a custom group (you'll also need to add a 3rd argument to createApiResponse() with this same argument).

2) But, there is one other thing that is troubling me. You said:

>Response from GET /api/joboffer/1
>...
>["image"]=>
>object(stdClass)#6405 (0) {
>}
>...

The weird part about this is the stdClass object. The image property should be a Media object - not an stdClass. I would double-check (by var_dump($jobOffer)) to make sure that this property is what you expect. I also found it strange that it printed this string "object(stdClass)#6405 (0) {" in ISON. That's not JSON - that's the result of var_dump(). What does the full JSON response look like? I think something else is not quite right...

Cheers!