config.yml

fos_rest:
    param_fetcher_listener: true
    body_converter:
        enabled: false
    service:
        serializer: jms_serializer.serializer
    view:
        formats:
            json: true
            xml: false
            html: false
        view_response_listener: force
        failed_validation: HTTP_BAD_REQUEST
    access_denied_listener:
        json: true
#    format_listener: false
    routing_loader:
         include_format: false
         default_format: json
    body_listener:
         decoders:
            json: fos_rest.decoder.json
    exception:
         messages:
            Symfony\Component\HttpKernel\Exception\HttpException: true

jms_serializer:
    metadata:
        directories:
            - { path: %kernel.root_dir%/Resources/FOSUserBundle/serializer, namespace_prefix: 'FOS\UserBundle' }

nelmio_api_doc: ~

Controller.php

<?php

use FOS\RestBundle\Controller\Annotations\View;
use FOS\RestBundle\Controller\Annotations\Post;
use FOS\RestBundle\Controller\Annotations\Get;
use Symfony\Component\HttpKernel\Exception\HttpException;
use Nelmio\ApiDocBundle\Annotation\ApiDoc;

class Controller {
    /**
     * @ApiDoc(
     *  resource=true,
     *  description="get hospital affiliations list."
     * )
     * @Get("/get.affiliations")
     * @View(StatusCode=200)
     */
    public function getAffiliationsAction()
    {
        $em = $this->getDoctrine()->getManager();
        $affiliations = $em->getRepository('FSMyOnCallDocBundle:HospitalAffiliation')->findAll();

        return array_map(
          function ($affiliation) {
              return $affiliation->getName();
          },
          $affiliations
        );
    }
}