FOSRestBundle: partial response in function of attributes asked in the request

Question

Context

I found a lot of questions about partial API response with FOSRest and all the answers are based on the JMS serializer options (exlude, include, groups, etc). It works fine but I try to achieve something less "static".

Let's say I have a user with the following attributes: id username firstname lastname age sex

I retrieve this user with the endpoint GET /users/{id} and the following method:

/**
 * @View
 *
 * GET /users/{id}
 * @param integer $user (uses ParamConverter)
 */
public function getUserAction(User $user) {
    return $user;
}

The method returns the user with all his attributes.

Now I want to allow something like that: GET /users/{id}?attributes=id,username,sex

Question

Did I missed a functionality of FOSRestBUndle, JMSserializer or SensioFrameworkExtraBundle to achieve it automatically? An annotation, a method, a keyword in the request or something else?

Otherwise, what is the best way to achieve it?

Code

I thought to do something like that:

/**
 * @View
 * @QueryParam(name="attributes")
 *
 * GET /users/{id}
 *
 * @param integer $user (uses ParamConverter)
 */
public function getUserAction(User $user, $attributes) {
    $groups = $attributes ? explode(",", $attributes) : array("Default");

    $view = $this->view($user, 200)
        ->setSerializationContext(SerializationContext::create()->setGroups($groups));

    return $this->handleView($view);
}

And create a group for each attribute:

use JMS\Serializer\Annotation\Groups;

class User {

    /** @Groups({"id"}) */
    protected $id;

    /** @Groups({"username"}) */
    protected $username;

    /** @Groups({"firstname"}) */
    protected $firstname;

    //etc
}

Nannettenanni

Answer 1

You can do it like that through groups, as you've shown. Maybe a bit more elegant solution would be to implement your own ExclusionStrategy. @Groups and other are implementations of ExclusionStrategyInterface too.

So, say you called your strategy SelectFieldsStrategy. Once you implement it, you can add it to your serialization context very easy:

$context = new SerializationContext();
$context->addExclusionStrategy(new SelectFieldsStrategy(['id', 'name', 'someotherfield']));

Husserl

Do you know if there is a way to put all this logic in an annotation (directly inside @View or inside a new annotation)? Actually I need fields exclusion everywhere and the code will strictly be identical in each endpoint. I'm pretty new to php and symfony so if you have some links, I will appreciate it. :) – Nannettenanni

It's definitely possible but I have never made custom annotation so I can't really help you with implementation guidelines, you'll have to research that part yourself :) – Transilluminate

Answer 2

My implementation based on Igor's answer:

ExlusionStrategy:

use JMS\Serializer\Exclusion\ExclusionStrategyInterface;
use JMS\Serializer\Metadata\ClassMetadata;
use JMS\Serializer\Metadata\PropertyMetadata;
use JMS\Serializer\Context;

class FieldsExclusionStrategy implements ExclusionStrategyInterface {
    private $fields = array();

    public function __construct(array $fields) {
        $this->fields = $fields;
    }

    public function shouldSkipClass(ClassMetadata $metadata, Context $navigatorContext) {
        return false;
    }

    public function shouldSkipProperty(PropertyMetadata $property, Context $navigatorContext) {
        if (empty($this->fields)) {
            return false;
        }

        if (in_array($property->name, $this->fields)) {
            return false;
        }

        return true;
    }
}

Controller:

/**
 * @View
 * @QueryParam(name="fields")
 *
 * GET /users/{id}
 *
 * @param integer $user (uses ParamConverter)
 */
public function getUserAction(User $user, $fields) {
    $context = new SerializationContext();
    $context->addExclusionStrategy(new FieldsExclusionStrategy($fields ? explode(',', $fields) : array()));

    return $this->handleView($this->view($user)->setSerializationContext($context));
}

Endpoint:

GET /users/{id}?fields=id,username,sex

Nannettenanni

Any ideas on how to handle related entities with this approach? In the PropertyMetadata there doesn't seem to be any information that could indicate that given field is an object. – Effortful

I figured it out: $context->getDepth() could be used for this. In my case I'm checking if it's more than 1. – Effortful