SymfonyRest + JMSSerializer

bonjour tout le monde,

j'aurais une question pour les pro symfonyrest en fait j'ai un soucis avec JMSSerializer , mon soucis est que j'arrive pas a récupérer mon Discriminator dans un group ,(pour les exclusion) j'ai une classe user qui extends Customer + Coach (différents types d'utilisateurs) et j'ai besoin justement de l'attribut "type" pour mon app

classe user :

<?php
/**
 * User
 * @ORM\Entity(repositoryClass="UserBundle\Repository\UserRepository")
 * @ORM\Table(name="user")
 * @ORM\InheritanceType("JOINED")
 * @ORM\DiscriminatorColumn(name="type", type="string")
 * @ORM\DiscriminatorMap({"Customer" = "Customer", "Company" = "Company", "Coach" = "Coach"})
 * @JMS\Discriminator(field="type",  map={"Customer": "UserBundle\Entity\Customer", "Coach": "UserBundle\Entity\Coach"}, groups = {"DefaultUser"})<br> * @JMS\ExclusionPolicy("all")
 */
abstract class User extends BaseUser
{
    /**
     * @var int
     *
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="AUTO")
     * @JMS\Groups({"DefaultUser"})
     *
     */
    protected $id;

ma classe customer

<?php

namespace UserBundle\Entity;

use UserBundle\Entity\User as User;
use Doctrine\ORM\Mapping as ORM;
use PUGX\MultiUserBundle\Validator\Constraints\UniqueEntity;
use JMS\Serializer\Annotation\ExclusionPolicy;
use JMS\Serializer\Annotation\Expose;
use JMS\Serializer\Annotation as JMS;

/**
 * Customer
 * @ORM\Entity
 * @ORM\Table(name="customer")
 * @UniqueEntity(fields = "username", targetClass = "UserBundle\Entity\User", message="fos_user.username.already_used")
 * @UniqueEntity(fields = "email", targetClass = "UserBundle\Entity\User", message="fos_user.email.already_used")
 * @ExclusionPolicy("all")
 *
 */
class Customer extends User
{
    /**
     * @var int
     *
     * @Expose
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="AUTO")
     * @JMS\Groups({"DefaultUser"})
     */
    protected $id;

class coach

<?php

namespace UserBundle\Entity;

use Doctrine\ORM\Mapping as ORM;
use UserBundle\Entity\User as User;
use PUGX\MultiUserBundle\Validator\Constraints\UniqueEntity;
use JMS\Serializer\Annotation\ExclusionPolicy;
use JMS\Serializer\Annotation\Expose;
use JMS\Serializer\Annotation\Groups;
use JMS\Serializer\Annotation\VirtualProperty;
use JMS\Serializer\Annotation as JMS;
/**
 * Coach
 * @ORM\Entity
 * @ORM\Table(name="coach")
 * @UniqueEntity(fields = "username", targetClass = "UserBundle\Entity\User", message="fos_user.username.already_used")
 * @UniqueEntity(fields = "email", targetClass = "UserBundle\Entity\User", message="fos_user.email.already_used")
 *
 */
class Coach extends User
{
    /**
     * @var int
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @Expose
     * @ORM\GeneratedValue(strategy="AUTO")
     * @JMS\Groups({"DefaultUser"})
     */
    protected $id;