验证约束不会触发注册表

我有一个Doctrine用户实体，我正试图为注册表添加表单验证器，但在任何情况下都不会为注册表触发。

我的用户实体：

namespace JMSHockey'AppBundle'Entity;
use Doctrine'ORM'Mapping as ORM;
use Symfony'Component'Security'Core'User'AdvancedUserInterface;
use Symfony'Component'Validator'Constraints as Assert;
use Symfony'Bridge'Doctrine'Validator'Constraints'UniqueEntity;
/**
 * My'AppBundle'Entity'User
 *
 * @ORM'Table(name="user")
 * @ORM'Entity(repositoryClass="My'AppBundle'Entity'UserRepository")
 * @UniqueEntity(fields={"email"}, message="Sorry, this email address is already in use.", groups={"registration"})
 * @UniqueEntity(fields={"username"}, message="Sorry, this username is already taken.", groups={"registration"})
 */
class User implements AdvancedUserInterface,'Serializable
{
    /**
     * @var integer $id
     *
     * @ORM'Column(name="id", type="integer", nullable=false)
     * @ORM'Id
     * @ORM'GeneratedValue(strategy="IDENTITY")
     */
    private $id;
    /**
     * @var string $email
     *
     * @ORM'Column(name="email", type="string", length=75, nullable=false)
     * @Assert'Email()
     * @Assert'NotBlank()
     */
    private $email;
    /**
     * @var string $username
     *
     * @ORM'Column(name="username", type="string", length=75, nullable=false)
     * @Assert'NotBlank()
     */
    private $username;
    ...
    }

这是我的UserType表单：

namespace My'AppBundle'Form'Type;
use Symfony'Component'Form'AbstractType;
use Symfony'Component'Form'FormBuilderInterface;
class UserType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder->add('email','email');
        $builder->add('username','text');
        ...
    }
    public function getDefaultOptions(array $options)
    {
        return array(
            'data_class' => 'My'AppBundle'Entity'User',
            'validation_groups' => array('registration'),
        );
    }
    public function getName()
    {
        return 'user';
    }
}

最后，注册表格：

namespace My'AppBundle'Form'Type;
use Symfony'Component'Form'AbstractType;
use Symfony'Component'Form'FormBuilderInterface;
class RegistrationType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder->add('user', new UserType());
    }
    public function getName()
    {
        return 'registration';
    }
}

我似乎在这里遗漏了一些明显的东西，但在Symfony手册和我在网上找到的资源之间，我还无法确定它是什么。