Generating LiipImagineBundle media URIs for FOSRestBundle Api using JMSSerializerBundle

config.yml

liip_imagine:
    filter_sets:
        thumbnail_name:
            quality: 95
            filters:
                thumbnail: { size: [120, 90], mode: inset }

Entity.php

<?php

namespace Acme\AcmeDemoBundle\Entity;

use JMS\Serializer\Annotation as Serializer;

/**
 * Entity
 *
 * @Serializer\ExclusionPolicy("all")
 */
class Entity
{
    /**
     * @var string|null
     *
     *
     * @Serializer\Expose
     * @Serializer\Accessor(getter="getBackgroundFilenameForSerialization")
     * @Serializer\Type("Filename")
     * @Serializer\SerializedName("background_uri")
     */
    private $backgroundFilename;

    /**
     * @return Media
     */
    public function getBackgroundFilenameForSerialization()
    {
        return new Filename($this->backgroundFilename);
    }
}

Filename.php

<?php

namespace Acme\AcmeDemoBundle\Entity;

/**
 * Class Filename
 * 
 * JMSSerializer Handler requires type to be custom class (it cannot be a primitive)
 * 
 */
class Filename {

    /**
     * @var string
     */
    public $filename;

    public function __construct($filename)
    {
        $this->setFilename($filename);
    }

    /**
     * @param string $name
     * @return Filename
     */
    public function setFilename($name)
    {
        $this->name = $name;
        
        return $this;
    }

    /**
     * @return string filename
     */
    public function getFilename()
    {
        return $this->filename;
    }

    /**
     * @return string filename
     */
    public function __toString()
    {
        return $this->filename;
    }

}

FilenameHandler.php

<?php

namespace Acme\AcmeDemoBundle\Handler;

use Acme\AcmeDemoBundle\Entity\Filename;
use JMS\Serializer\GraphNavigator;
use JMS\Serializer\Handler\SubscribingHandlerInterface;
use JMS\Serializer\VisitorInterface;
use Liip\ImagineBundle\Imagine\Cache\CacheManager;

class FilenameHandler implements SubscribingHandlerInterface
{

    function __construct(CacheManager $manager)
    {
        $this->manager = $manager;
    }

    public static function getSubscribingMethods()
    {
        return array(
            array(
                'direction' => GraphNavigator::DIRECTION_SERIALIZATION,
                'format' => 'json',
                'type' => 'Filename',
                'method' => 'serializeFilenameToJson',
            ),
        );
    }

    public function serializeFilenameToJson(VisitorInterface $visitor, Filename $filename, array $type)
    {
        return $this->manager->getBrowserPath($filename, 'thumbnail_name', true);
    }
}

services.yml

acme.serializer.filename_handler:
    class: Acme\AcmeDemoBundle\Handler\FilenameHandler
    arguments:
        - "@liip_imagine.cache.manager"
    tags:
        - { name: 'jms_serializer.handler', type: Filename, format: json}