有没有办法将聚合/计算字段(concat)添加到Doctrine实体？

use Doctrine\ORM\Mapping as ORM;

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

    /**
     * @ORM\Column(type="string")
     */
    private $concatenatedField;

    // ...
}

use Doctrine\ORM\Mapping as ORM;
use Doctrine\Common\EventSubscriber;
use Doctrine\ORM\Event\LifecycleEventArgs;

/**
 * @ORM\Entity
 */
class MyEntity implements EventSubscriber
{
    // ...

    /**
     * @ORM\Column(type="string")
     */
    private $field1;

    /**
     * @ORM\Column(type="string")
     */
    private $field2;

    /**
     * @ORM\Column(type="string")
     */
    private $concatenatedField;

    // ...

    public function getSubscribedEvents()
    {
        return ['prePersist', 'preUpdate'];
    }

    public function prePersist(LifecycleEventArgs $args)
    {
        $entity = $args->getEntity();
        $entity->concatenatedField = $entity->field1 . $entity->field2;
    }

    public function preUpdate(LifecycleEventArgs $args)
    {
        $entity = $args->getEntity();
        $entity->concatenatedField = $entity->field1 . $entity->field2;
    }

    // ...
}