Hibernate 版本控制父实体

Question

考虑两个实体 Parent 和 Child。

• 子项是父项临时集合的一部分
• 子级使用 FetchType.LAZY 映射到父级的 ManyToOne

两者都在同一个表单上显示给用户。当用户保存数据时，我们首先更新父实例，然后更新子集合（都使用合并）。

现在是棘手的部分。当用户仅修改表单上的子属性时，休眠脏检查不会更新父实例，因此不会增加该实体的乐观锁定版本号。

我想看看只有 Parent 被版本化的情况，每次我为 Parent 调用 merge 然后版本总是更新，即使在 db 中没有执行实际更新。

Answer 1

您可以将更改从子实体传播到父实体。这要求您在修改子实体时传播OPTIMISTIC_FORCE_INCREMENT 锁。

因此，您需要让所有实体都实现RootAware 接口：

public interface RootAware<T> {
    T root();
}

@Entity(name = "Post") 
@Table(name = "post")
public class Post {
 
    @Id
    private Long id;
 
    private String title;
 
    @Version
    private int version;
 
    //Getters and setters omitted for brevity
}
 
@Entity(name = "PostComment")
@Table(name = "post_comment")
public class PostComment 
    implements RootAware<Post> {
 
    @Id
    private Long id;
 
    @ManyToOne(fetch = FetchType.LAZY)
    private Post post;
 
    private String review;
 
    //Getters and setters omitted for brevity
 
    @Override
    public Post root() {
        return post;
    }
}
 
@Entity(name = "PostCommentDetails")
@Table(name = "post_comment_details")
public class PostCommentDetails 
    implements RootAware<Post> {
 
    @Id
    private Long id;
 
    @ManyToOne(fetch = FetchType.LAZY)
    @MapsId
    private PostComment comment;
 
    private int votes;
 
    //Getters and setters omitted for brevity
 
    @Override
    public Post root() {
        return comment.getPost();
    }
}

那么，你需要两个事件监听器：

public static class RootAwareInsertEventListener 
    implements PersistEventListener {
 
    private static final Logger LOGGER = 
        LoggerFactory.getLogger(RootAwareInsertEventListener.class);
 
    public static final RootAwareInsertEventListener INSTANCE = 
        new RootAwareInsertEventListener();
 
    @Override
    public void onPersist(PersistEvent event) throws HibernateException {
        final Object entity = event.getObject();
 
        if(entity instanceof RootAware) {
            RootAware rootAware = (RootAware) entity;
            Object root = rootAware.root();
            event.getSession().lock(root, LockMode.OPTIMISTIC_FORCE_INCREMENT);
 
            LOGGER.info("Incrementing {} entity version because a {} child entity has been inserted", root, entity);
        }
    }
 
    @Override
    public void onPersist(PersistEvent event, Map createdAlready) 
        throws HibernateException {
        onPersist(event);
    }
}

和

public class RootAwareUpdateAndDeleteEventListener
    implements FlushEntityEventListener {
 
    private static final Logger LOGGER =
        LoggerFactory.getLogger(RootAwareUpdateAndDeleteEventListener.class);
 
    public static final RootAwareUpdateAndDeleteEventListener INSTANCE =
        new RootAwareUpdateAndDeleteEventListener();
 
    @Override
    public void onFlushEntity(FlushEntityEvent event) throws HibernateException {
        final EntityEntry entry = event.getEntityEntry();
        final Object entity = event.getEntity();
        final boolean mightBeDirty = entry.requiresDirtyCheck( entity );
 
        if(mightBeDirty && entity instanceof RootAware) {
            RootAware rootAware = (RootAware) entity;
            if(updated(event)) {
                Object root = rootAware.root();
                LOGGER.info("Incrementing {} entity version because a {} child entity has been updated",
                    root, entity);
                incrementRootVersion(event, root);
            }
            else if (deleted(event)) {
                Object root = rootAware.root();
                LOGGER.info("Incrementing {} entity version because a {} child entity has been deleted",
                    root, entity);
                incrementRootVersion(event, root);
            }
        }
    }
 
    private void incrementRootVersion(FlushEntityEvent event, Object root) {
        event.getSession().lock(root, LockMode.OPTIMISTIC_FORCE_INCREMENT);
    }
 
    private boolean deleted(FlushEntityEvent event) {
        return event.getEntityEntry().getStatus() == Status.DELETED;
    }
 
    private boolean updated(FlushEntityEvent event) {
        final EntityEntry entry = event.getEntityEntry();
        final Object entity = event.getEntity();
 
        int[] dirtyProperties;
        EntityPersister persister = entry.getPersister();
        final Object[] values = event.getPropertyValues();
        SessionImplementor session = event.getSession();
 
        if ( event.hasDatabaseSnapshot() ) {
            dirtyProperties = persister.findModified(
                event.getDatabaseSnapshot(), values, entity, session
            );
        }
        else {
            dirtyProperties = persister.findDirty(
                values, entry.getLoadedState(), entity, session
            );
        }
 
        return dirtyProperties != null;
    }
}

您可以按如下方式注册：

public class RootAwareEventListenerIntegrator
    implements org.hibernate.integrator.spi.Integrator {
 
    public static final RootAwareEventListenerIntegrator INSTANCE = 
        new RootAwareEventListenerIntegrator();
 
    @Override
    public void integrate(
            Metadata metadata,
            SessionFactoryImplementor sessionFactory,
            SessionFactoryServiceRegistry serviceRegistry) {
 
        final EventListenerRegistry eventListenerRegistry =
                serviceRegistry.getService( EventListenerRegistry.class );
 
        eventListenerRegistry.appendListeners(EventType.PERSIST, RootAwareInsertEventListener.INSTANCE);
        eventListenerRegistry.appendListeners(EventType.FLUSH_ENTITY, RootAwareUpdateAndDeleteEventListener.INSTANCE);
    }
 
    @Override
    public void disintegrate(
            SessionFactoryImplementor sessionFactory,
            SessionFactoryServiceRegistry serviceRegistry) {
        //Do nothing
    }
}

然后通过 Hibernate 配置属性提供 RootAwareFlushEntityEventListenerIntegrator：

configuration.put(
    "hibernate.integrator_provider", 
    (IntegratorProvider) () -> Collections.singletonList(
        RootAwareEventListenerIntegrator.INSTANCE
    )
);

现在，当您修改 PostCommentDetails 实体时：

PostCommentDetails postCommentDetails = entityManager.createQuery(
    "select pcd " +
    "from PostCommentDetails pcd " +
    "join fetch pcd.comment pc " +
    "join fetch pc.post p " +
    "where pcd.id = :id", PostCommentDetails.class)
.setParameter("id", 2L)
.getSingleResult();
 
postCommentDetails.setVotes(15);

父Post实体版本也被修改：

SELECT  pcd.comment_id AS comment_2_2_0_ ,
        pc.id AS id1_1_1_ ,
        p.id AS id1_0_2_ ,
        pcd.votes AS votes1_2_0_ ,
        pc.post_id AS post_id3_1_1_ ,
        pc.review AS review2_1_1_ ,
        p.title AS title2_0_2_ ,
        p.version AS version3_0_2_
FROM    post_comment_details pcd
INNER JOIN post_comment pc ON pcd.comment_id = pc.id
INNER JOIN post p ON pc.post_id = p.id
WHERE   pcd.comment_id = 2
 
UPDATE post_comment_details 
SET votes = 15 
WHERE comment_id = 2
 
UPDATE post 
SET version = 1 
where id = 1 AND version = 0

Answer 2

我想我明白了。调用合并后，将返回附加的实例引用。当我使用 entityManager.lock(updated, LockModeType.WRITE); 获得显式锁定时然后即使父实例未在 db 中更新，版本号也会增加。

此外，我将分离实例版本与持久实例版本进行比较。如果它们不匹配，则 Parent 已在 db 中更新，并且版本号也已更改。这使版本号保持一致。否则 entityManager.lock 会增加版本号，即使合并操作改变了它。

仍在寻找解决方案如何在合并期间实体不脏时使休眠增加版本。

Answer 3

我认为您不能强制休眠为未更改的对象增加版本号，因为如果没有任何更改（出于显而易见的原因），它将不会执行任何 db UPDATE 查询。

您可以做一些令人讨厌的 hack，例如向对象添加一个新字段并手动递增该字段，但就个人而言，这似乎是在浪费时间和资源。我会选择您的显式锁定解决方案，因为这似乎可以满足您的需求，而无需不必要的黑客攻击。

Answer 4

我刚刚实现了类似的东西，它像野兽一样又快又好。 目前您正在保存您的“孩子”，只需调用执行以下操作：

save(child);
T parent = child.getParentEntity();
entityManager.lock(parent, LockModeType.OPTIMISTIC_FORCE_INCREMENT);

您需要访问可以在 spring 中获得的实体管理器，例如：

  @PersistenceContext
  private EntityManager entityManager;

你的父实体应该有来自 javax.persistence.Version 的 @Version 而不是 spring 的。 （我假设在孩子保存时刻，您将完成所有验证和操作，因此当您保存孩子时，父母肯定会变脏）