queryBuilder symfony 3上的ManyToOne

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity
 */
class User
{
    // ...

    /**
     * @ORM\ManyToOne(targetEntity="Role")
     * @ORM\JoinColumn(name="role_id", referencedColumnName="id")
     */
    private $role;

    // ...
}

use Doctrine\ORM\EntityManagerInterface;

class UserController
{
    private $entityManager;

    public function __construct(EntityManagerInterface $entityManager)
    {
        $this->entityManager = $entityManager;
    }

    public function getUsersWithRole($roleId)
    {
        $queryBuilder = $this->entityManager->createQueryBuilder();

        $queryBuilder
            ->select('u')
            ->from('User', 'u')
            ->where('u.role = :roleId')
            ->setParameter('roleId', $roleId);

        $users = $queryBuilder->getQuery()->getResult();

        // 处理查询结果...
    }
}