Symfony Paginator，错误@Enum

Question

我正在尝试使用Doctrine和Doctrine类Paginator在查询中添加分页：

    $qb = $this->_em->createQueryBuilder();
    $qb->select(array('a.id'))
            ->from('MyProjectBundle:Account', 'a')
            ->leftjoin('a.first', 'fd')
            ->leftjoin('a.second', 'fr')
            ->where('a != ?1')
            ->setParameters(array(1 => $account))
            ->setFirstResult(($page-1) * $per_page)
            ->setMaxResults($per_page);

就像在Paginator的文档中一样，我这样做：

return new Paginator($qb);

我有这个错误：

{

    "code": 500,
    "message": "[Semantical Error] The annotation \"@Enum\" in property Doctrine\\ORM\\Mapping\\GeneratedValue::$strategy was never imported. Did you maybe forget to add a \"use\" statement for this annotation?"

}

我包含use Doctrine\ORM\Tools\Pagination\Paginator;，我不知道为什么会出现此错误？