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java – hibernate乐观锁和集合的麻烦

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我在使用乐观锁定方面遇到了麻烦.我有一个持久对象,版本号.我希望只有在我的持久对象“真正”更新时才会增加此版本号,这意味着当一个或多个字段被修改或者在数据库中修改了在我的实体中使用@ManyToOne或@OneToMany注释映射的集合时.
发生的情况是,只有当我的实体中直接包含的字段发生更改时才会增加版本,而不会在集合发生更改时增加.

注意：我在实体注释中添加了select-before-update.不知道它是否会改变集合版本控制的行为！
我还有一个字段不应该影响我的实体中的版本,我在其上放置了@OptimisticLock(exclude = true)注释.

有谁知道我怎么可能尝试使我的版本工作？根据我在几个论坛上读到的内容,当集合发生变化时,版本号应该会自动增加.为什么不是我的情况呢？任何的想法？

解决方法:

只有单向集合更改才会传播到父实体版本as explained in this article.因为您使用的是双向关联,所以@ManyToOne将控制此关联,因此在父级集合中添加/删除实体不会影响父实体版本.

但是,您仍然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.

This article详细解释了您应该如何实现这样一个用例.

简而言之,您需要让所有实体实现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();
    }
}

然后,您需要两个事件侦听器：

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 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);
    }
}

您可以注册如下：

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

PostComment实体也是如此.

即使您插入一个新的子实体,它也可以工作：

Post post = entityManager.getReference(Post.class, 1L);

PostComment postComment = new PostComment();
postComment.setId(3L);
postComment.setReview("Worth it!");
postComment.setPost(post);
entityManager.persist(postComment);

Hibernate管理以正确地增加父实体：

SELECT p.id AS id1_0_0_ ,
       p.title AS title2_0_0_ ,
       p.version AS version3_0_0_
FROM   post p
WHERE  p.id = 1

INSERT INTO post_comment (post_id, review, id) 
VALUES (1, 'Worth it!', 3)

UPDATE post 
SET version = 3 
WHERE id = 1 AND version = 2

它在删除子实体时也有效：

PostComment postComment = entityManager.getReference(PostComment.class, 3l);
entityManager.remove(postComment);

Hibernate也在这个用例中管理增加父实体：

SELECT pc.id AS id1_1_0_ ,
       pc.post_id AS post_id3_1_0_ ,
       pc.review AS review2_1_0_
FROM   post_comment pc
WHERE  pc.id = 3

SELECT p.id AS id1_0_0_ ,
       p.title AS title2_0_0_ ,
       p.version AS version3_0_0_
FROM   post p
WHERE  p.id = 1

DELETE FROM post_comment 
WHERE id = 3

UPDATE post 
SET version = 4 
WHERE id = 1 and version = 3

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