Symfony 2 authentication with Entity error
security:
    firewalls:
        secured_area:
            pattern:    ^/
            anonymous: ~
            form_login: true
            logout:
                path:   /logout
                target: /login

#    access_control:
#        - { path: ^/login, roles: IS_AUTHENTICATED_ANONYMOUSLY }
#        - { path: ^/admin, roles: ROLE_ADMIN }

    providers:
        in_memory:
            users:
                admin: { password: admin, roles: 'ROLE_ADMIN' }

        main:
            entity: { class: MyAppSafeDrivingBundle:Client, property: username }

    encoders:
        SymfonyComponentSecurityCoreUserUser: plaintext
        MyAppSafeDrivingBundleEntityClient: plaintext

security:
    firewalls:
        secured_area:
            pattern:    ^/
            anonymous: ~
            form_login: true
            logout:
                path:   /logout
                target: /login

    access_control:
        - { path: ^/login, roles: IS_AUTHENTICATED_ANONYMOUSLY }
        - { path: ^/admin, roles: ROLE_ADMIN }

    providers:
        in_memory:
            users:
                admin: { password: admin, roles: 'ROLE_ADMIN' }
                client: { password: client, roles: 'ROLE_CLIENT' }
                formateur: { password: formateur, roles: 'ROLE_FORMATEUR' }
                agence: { password: agence, roles: 'ROLE_AGENCE' }

        main:
            entity: { class: MyAppSafeDrivingBundle:Client, property: username }

    encoders:
        SymfonyComponentSecurityCoreUserUser: plaintext
        MyAppSafeDrivingBundleEntityClient: plaintext

<?php

namespace MyAppSafeDrivingBundleEntity;
use DoctrineORMMapping as ORM;
use SymfonyComponentValidatorConstraints as Assert;
use SymfonyComponentSecurityCoreUserUserInterface;

/**
 * @ORMEntity(repositoryClass="MyAppSafeDrivingBundleRepositoryUserRepository")
 */
class Client implements UserInterface
{
    /**
     * @ORMGeneratedValue
     * @ORMId
     * @ORMColumn(type="integer")
     */
    protected $id;

    /**
     * @ORMColumn(type="string", length="32", unique=true)
     */
    protected $username;

    /**
     * @ORMColumn(type="string", length="255")
     */
    protected $password;


    /**
     * @ORMColumn(type="string", length="255")
     * @AssertNotBlank()
     */
    private $mail;

    /**
     * @ORMColumn(type="string",length="255")
     * @AssertNotBlank()
     * @AssertMinLength(3)
     */
    private $nom;

    /**
     * @ORMColumn(type="string",length="255")
     * @AssertNotBlank()
     * @AssertMinLength(3)
     */
    private $prenom;

    /**
     * @ORMColumn(type="date")
     * @AssertNotBlank()
     */
    private $dateNaissance;

    /**
     * @ORMColumn(type="string", length="255")
     * @AssertNotBlank()
     */
    private $adresse;

    /**
     * @ORMColumn(type="string", length="255")
     * @AssertNotBlank()
     */
    private $telephone;

    /**
     * @ORMManyToOne(targetEntity="Agence")
     */
    private $agence;

    /**
     * @ORMManyToOne(targetEntity="Offre")
     */
    private $offre;


    /**
     * @ORMColumn(type="string",length="1")
     * @AssertNotBlank()
     * @AssertChoice(choices = {"M", "F"})
     */
    private $sexe;

    /**
     * @ORMColumn(type="string",length="255")
     * @AssertNotBlank()
     */
    private $nomCommercial;

    /**
     * Get id
     *
     * @return integer $id
     */
    public function getId()
    {
        return $this->id;
    }

    public function getUsername()
    {
    return $this->username;
    }

    public function setUsername($username)
    {
        $this->username = $username;
    }

    /**
     * Gets the user password.
     *
     * @return string The password.
     */
    public function getPassword()
    {
        return $this->password;
    }

    /**
     * Sets the user password.
     *
     * @param string $value The password.
     */
    public function setPassword($password)
    {
        $this->password = $password;
    }

    /**
     * Set nom
     *
     * @param string $nom
     */
    public function setNom($nom)
    {
        $this->nom = $nom;
    }

    /**
     * Get nom
     *
     * @return string $nom
     */
    public function getNom()
    {
        return $this->nom;
    }

    /**
     * Set prenom
     *
     * @param string $prenom
     */
    public function setPrenom($prenom)
    {
        $this->prenom = $prenom;
    }

    /**
     * Get prenom
     *
     * @return string $prenom
     */
    public function getPrenom()
    {
        return $this->prenom;
    }

    /**
     * Set dateNaissance
     *
     * @param date $dateNaissance
     */
    public function setDateNaissance($dateNaissance)
    {
        $this->dateNaissance = $dateNaissance;
    }

    /**
     * Get dateNaissance
     *
     * @return date $dateNaissance
     */
    public function getDateNaissance()
    {
        return $this->dateNaissance;
    }

    /**
     * Set sexe
     *
     * @param string $sexe
     */
    public function setSexe($sexe)
    {
        $this->sexe = $sexe;
    }

    /**
     * Get sexe
     *
     * @return string $sexe
     */
    public function getSexe()
    {
        return $this->sexe;
    }

    /**
     * Get mail
     *
     * @return string $mail
     */
    public function getMail()
    {
        return $this->mail;
    }

    /**
     * Set mail
     *
     * @param string $mail
     */
    public function setMail($mail)
    {
        $this->mail = $mail;
    }

    /**
     * Set adresse
     *
     * @param string $adresse
     */
    public function setAdresse($adresse)
    {
        $this->adresse = $adresse;
    }

    /**
     * Get adresse
     *
     * @return string $adresse
     */
    public function getAdresse()
    {
    return $this->adresse;
    }

    /**
     * Set telephone
     *
     * @param string $telephone
     */
    public function setTelephone($telephone)
    {
        $this->telephone = $telephone;
    }

    /**
     * Get telephone
     *
     * @return string $telephone
     */
    public function getTelephone()
    {
        return $this->telephone;
    }

    /**
     * Set agence
     *
     * @param MyAppSafeDrivingBundleEntityAgence $agence
     */
    public function setAgence(MyAppSafeDrivingBundleEntityAgence $agence)
    {
        $this->agence = $agence;
    }

    /**
     * Get agence
     *
     * @return MyAppSafeDrivingBundleEntityAgence $agence
     */
    public function getAgence()
    {
        return $this->agence;
    }

    /**
     * Set offre
     *
     * @param MyAppSafeDrivingBundleEntityOffre $offre
     */
    public function setOffre(MyAppSafeDrivingBundleEntityOffre $offre)
    {
        $this->offre = $offre;
    }

    /**
     * Get offre
     *
     * @return MyAppSafeDrivingBundleEntityOffre $offre
     */
    public function getOffre()
    {
        return $this->offre;
    }

    /**
     * Set nomCommercial
     *
     * @param string $nomCommercial
     */
    public function setNomCommercial($nomCommercial)
    {
        $this->nomCommercial = $nomCommercial;
    }

    /**
     * Get nomCommercial
     *
     * @return string $nomCommercial
     */
    public function getNomCommercial()
    {
        return $this->nomCommercial;
    }

    /**
     * Implementing the UserInterface interface
     */

    public function __toString()
    {
        return $this->getUsername();
    }

    public function getRoles()
    {
        return array('ROLE_CLIENT');
    }

    public function eraseCredentials()
    {
        return false;
    }

    public function getSalt()
    {
        return '';
    }

    /**
     * equals.
     *
     * @param UserInterface $account
     * @return bool
     */
    public function equals(UserInterface $account)
    {
        if ($account->getUsername() != $this->getUsername) {
            return false;
        }
        if ($account->getMail() != $this->getMail) {
            return false;
        }
        return true;
    }
}

<?php
namespace MyAppSafeDrivingBundleRepository;
use DoctrineORMEntityRepository;
use SymfonyComponentSecurityCoreUserUserProviderInterface;
use SymfonyComponentSecurityCoreUserUserInterface;

class UserRepository extends EntityRepository implements UserProviderInterface
{
    const CREATED  = 0;
    const ACTIVE   = 10;
    const INACTIVE = 20;
    /**
     * loadUserByUsername.
     *
     * @param string $username
     * @return MyAppSafeDrivingBundleEntityClient
     */
    public function loadUserByUsername($username)
    {
        return $this->findOneBy(array('username' => $username));
    }
    function loadUser(UserInterface $user)
    {
        return $user;
    }
    function loadUserByAccount(AccountInterface $account)
    {
        return $this->loadUserByUsername($account->getUsername());
    }
    public function supportsClass($class)
    {
        return true;
    }
}