Doctrine2 ManyToMany 不执行侦听器事件

And my doctrine2 classes are defined like this:

/**
 * @var Roles
 *
 * @ORMManyToMany(targetEntity="SecRole")
 * @ORMJoinTable(name="SEC_USER_ROLE",
 *      joinColumns={@ORMJoinColumn(name="SEC_USER_ID", referencedColumnName="SEC_USER_ID")},
 *      inverseJoinColumns={@ORMJoinColumn(name="SEC_ROLE_ID", referencedColumnName="SEC_ROLE_ID")}
 *      )
 */
private $userRoles;

public function __construct() {
  parent::__construct();
  $this->userRoles = new DoctrineCommonCollectionsArrayCollection();
}

public function addSecRole(myEntitySecRole $role)
{
  $exists = $this->userRoles->exists(function($key, $elem) use($role) {
      return isset($elem) && $elem->getSecRoleCode() == $role->getSecRoleCode();
    });
  return !$exists && $this->userRoles->add($role);
}

要向用户添加新角色，我执行以下操作:

  $r = $rolerep->findOneBySecRoleCode('SystemAdmin');
  $u = $userrep->findOneByUserLogin('sysadmin');
  if (isset($r) && isset($u))
  {
    if ($u->addSecRole($r)) {
      $em->flush();
    }
  }