Doctrine在插入后拒绝更新

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

/**
 * @ORM\Entity
 * @ORM\Table(name="my_entity")
 */
class MyEntity implements EventSubscriber
{
    /**
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="AUTO")
     * @ORM\Column(type="integer")
     */
    private $id;

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

    /**
     * @ORM\Column(type="boolean")
     */
    private $isInserted = false;

    /**
     * @ORM\PrePersist
     */
    public function prePersist()
    {
        $this->isInserted = true;
    }

    /**
     * @ORM\PreUpdate
     */
    public function preUpdate()
    {
        if ($this->isInserted) {
            throw new \Exception("Object cannot be updated after insertion.");
        }
    }

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

    // Getters and setters...
}

// 在使用时，可以像下面这样进行操作：

$entityManager = // 获取EntityManager实例

$entity = new MyEntity();
$entity->setName("Example");

$entityManager->persist($entity);
$entityManager->flush(); // 执行插入操作

$entity->setName("Updated Example");

$entityManager->flush(); // 在这里会抛出异常，因为对象已经被插入过，不允许更新