How do I create a custom exclusion strategy for JMS Serializer that allows me to make run-time decisions about whether to include a particular field?

Question

As the title says, I am trying to make a run-time decision on whether or not to include fields in the serialization. In my case, this decision will be based on permissions.

I am using Symfony 2, so what I'm looking to do is add an additional annotation called @ExcludeIf which accepts a security expression.

I can handle the annotation parsing and storing of the meta data, but I am not able to see how to integrate a custom exclusion strategy with the library.

Any suggestions?

Note: exclusion strategies are an actual construct in the JMS codebase, I just haven't been able to figure out the best way to integrate an extra on top of the others

PS: I had asked about this before and was pointed to using groups. For various reasons this is a very poor solution for my needs.

Answer 1

You just have to create a class that implements JMS\Serializer\Exclusion\ExclusionStrategyInterface

<?php

namespace JMS\Serializer\Exclusion;

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

interface ExclusionStrategyInterface
{
    /**
     * Whether the class should be skipped.
     *
     * @param ClassMetadata $metadata
     *
     * @return boolean
     */
    public function shouldSkipClass(ClassMetadata $metadata, Context $context);

    /**
     * Whether the property should be skipped.
     *
     * @param PropertyMetadata $property
     *
     * @return boolean
     */
    public function shouldSkipProperty(PropertyMetadata $property, Context $context);
}

In your case, you can implement your own custom logic in the shouldSkipProperty method and always return false for shouldSkipClass.

Example of implementation can be found in the JMS/Serializer repository

We will reference the created service as acme.my_exclusion_strategy_service below.

---

In your controller action:

<?php

use Symfony\Component\HttpFoundation\Response;
use JMS\Serializer\SerializationContext;

// ....

$context = SerializationContext::create()
    ->addExclusionStrategy($this->get('acme.my_exclusion_strategy_service'));

$serial = $this->get('jms_serializer')->serialize($object, 'json', $context);

return new Response($serial, Response::HTTP_OK, array('Content-Type' => 'application/json'));

Or if you are using FOSRestBundle

<?php

use FOS\RestBundle\View;
use JMS\Serializer\SerializationContext;

// ....

$context = SerializationContext::create()
    ->addExclusionStrategy($this->get('acme.my_exclusion_strategy_service'))

$view = new View($object);
$view->setSerializationContext($context);

// or you can create your own view factory that handles the creation
// of the context for you

return $this->get('fos_rest.view_handler')->handle($view);