JPA/Hibernate 级联删除不起作用

Question

我有这些实体：

@Entity
public class Item extends Unit
{
    // @Id is in superclass

    @OneToMany(mappedBy = "parent", cascade = CascadeType.ALL, orphanRemoval = true)
    private Set<ItemRelation> lowerItemRelations = new LinkedHashSet<>();

    @OneToMany(mappedBy = "child", cascade = CascadeType.ALL, orphanRemoval = true)
    private Set<ItemRelation> higherItemRelations = new LinkedHashSet<>();

    // this too is in superclass
    @OneToMany(mappedBy = "unit", cascade = CascadeType.REMOVE, orphanRemoval = true)
    @OrderBy("date")
    protected Set<UnitRegistration> registrations = new LinkedHashSet<>();

    ...
}

@Entity
@Table(name = "ITEM_RELATION",
    indexes = @Index(columnList = "PARENT_ID, CHILD_ID", unique = true))
public class ItemRelation extends AbstractEntity
{
    // @Id is in superclass

    @ManyToOne(optional = false)
    @JoinColumn(name = "PARENT_ID")
    private Item parent;

    @ManyToOne(optional = false)
    @JoinColumn(name = "CHILD_ID")
    private Item child;

    @NotNull
    @Min(0)
    @Column(nullable = false, columnDefinition = "INT DEFAULT 1 NOT NULL")
    private int quantity = 1;

    ...
}

现在我只想执行一个简单的em.remove(item)，但是Hibernate 不会为lowerItemRelations/higherItemRelations 发出相关的DELETE 语句。

相反，对于所有其他带有 @OneToMany(mappedBy = "...", cascade = CascadeType.ALL/REMOVE, orphanRemoval=true) 注释的字段，它会发出语句。

这里有一点 MySQL 日志 sn-p:

2016-09-28T08:47:52.090453Z   13 Query  update UNIT set CODE='CE13000003167', ... where ID=132241 and version=1
2016-09-28T08:47:52.094971Z   13 Query  delete from UNIT_ACTION where PARENT_ID=132241
2016-09-28T08:47:52.134999Z   13 Query  update AUTHORIZATION set UNIT_ID=null where UNIT_ID=132241
2016-09-28T08:47:52.158014Z   13 Query  delete from UNIT_DOCUMENT where PARENT_ID=132241
2016-09-28T08:47:52.248074Z   13 Query  delete from UNIT_PRODUCT where UNIT_ID=132241
2016-09-28T08:47:52.315641Z   13 Query  delete from UNIT_PROJECT where UNIT_ID=132241
2016-09-28T08:47:52.586008Z   13 Query  delete from ITEM_ALTERNATIVE where ITEM_ID=132241
2016-09-28T08:47:52.853350Z   13 Query  delete from AUTHORIZATION where ID=714491
2016-09-28T08:47:52.910835Z   13 Query  delete from UNIT_REGISTRATION where ID=173505
2016-09-28T08:47:52.980887Z   13 Query  delete from UNIT where ID=132241 and version=1
2016-09-28T08:47:53.133290Z   13 Query  rollback

如您所见，没有可以从 ITEM_RELATION 中删除的行，我期待的是：

0000-00-00T00:00:00.000000Z   13 Query  delete from ITEM_RELATION where PARENT_ID=132241
0000-00-00T00:00:00.000000Z   13 Query  delete from ITEM_RELATION where CHILD_ID=132241

显然事务被回滚了，因为：

com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot delete or update a parent row: a foreign key constraint fails (`edea2`.`item_relation`, CONSTRAINT `FK_ITEM_RELATION_CHILD_ID` FOREIGN KEY (`CHILD_ID`) REFERENCES `unit` (`ID`)) 

另一个奇怪的事情是 Hibernate 执行（不必要的？）UPDATE 作为第一条语句。

然而，

• 这种不同的行为是否与 lowerItemRelations/higherItemRelations 引用相同的实体类型（尽管在不同的字段/列和不同的行上）这一事实有关？

• 这是一个错误还是有这种行为的原因？

我尝试了什么：

• 初始化集合
• 初始化并清除集合（以触发 orphanRemoval）
• em.remove()em.remove(item) 之前的每个集合元素

没有成功。

到目前为止我发现的唯一工作方式是发出：

CriteriaBuilder builder = em.getCriteriaBuilder();
CriteriaDelete<ItemRelation> delete = builder.createCriteriaDelete(ItemRelation.class);
Root<ItemRelation> rel = delete.from(ItemRelation.class);
delete.where(builder.or(
    builder.equal(rel.get(ItemRelation_.parent), managedItem),
    builder.equal(rel.get(ItemRelation_.child), managedItem)));

em.flush();

em.remove(managedItem);

我在 Wildfly 10.1.0.Final 上使用 Hibernate 5.2.2.Final

谢谢

---

这里的要求是 em.remove() 被调用的地方：

@Stateless
@Local
public class PersistenceService implements Serializable
{       
    @PersistenceContext
    private EntityManager em;

    ...

    @TransactionAttribute(TransactionAttributeType.REQUIRED)
    public <T> void delete(T entity)
    {
        T managed;

        if(!em.contains(entity))
        {
            Class<T> entityClass = EntityUtils.getClass(entity);
            Object entityId = EntityUtils.getIdentifier(entity);

            managed = em.find(entityClass, entityId);
        }
        else
        { 
            managed = entity;
        }

        em.remove(managed);

        // em.flush(); // just for debugging
    }
}

Answer 1

好的，这是一个错误。

我发现此行为与两个集合的延迟初始化有关，因此我提交了问题 HHH-11144 并生成了一个简单的测试用例（也可在 GitHub 上找到）。

简而言之，这种情况发生在

EntityManager em = emf.createEntityManager();
EntityTransaction tx = em.getTransaction();

tx.begin();

Item item = em.createQuery("select x from Item x where x.code = 'first'", Item.class).getSingleResult();

Set<ItemRelation> lowerItemRelations = item.getLowerItemRelations();
Hibernate.initialize(lowerItemRelations);

// initializing 'higherItemRelations' prevents orphanRemoval to work on 'lowerItemRelations'
Set<ItemRelation> higherItemRelations = item.getHigherItemRelations();
Hibernate.initialize(higherItemRelations);

lowerItemRelations.clear();

tx.commit();
em.close();

Answer 2

我敢打赌，Unit 正在引用其他内容，并且不是您的根用户独有的 - 在这种情况下为 ItemRelation，因此无法删除。

您的映射表明Unit 可以有多个ItemRelations，所以这很可能是这里的问题。您必须首先通过删除双方的相互引用来“破坏”关系（或者至少在持有 FK 的实体上，或者如果使用连接表，则其中任何一个）