如何从CollectionTable中删除数据休眠(Jpa) [英] How delete data from CollectionTable | Hibernate (Jpa)

问题描述

我有一个带有List<String> MyList的"A"实体:

i have "A" entity with List<String> MyList:

@Entity(name = "A_table")
@Inheritance(strategy=InheritanceType.JOINED)
public class A implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    private String RepresentativeName;

    @ElementCollection
    @CollectionTable(name = "MyList_Table")
    private List<String> MyList;
}

在将值"设置为此"A"实体后，我想从derby表中删除所有这些数据.
但是，如何从CollectionTable(MyList_Table)中删除字符串?

After i set Values to this "A" entity, i want to delete all this data from the derby table.
But how i can delete the Strings from the CollectionTable (MyList_Table)?

我尝试通过HQL查询使其成功，但出现错误.

I try to make it by HQL query, but i got error.

List<String> strList = em.createQuery("from MyList_Table").getResultList();
...
...   

错误:

MyList_Table is not mapped [from MyList_Table]

我应该如何正确地制定查询?
可能还有另一种删除此CollectionTable数据的方法吗?

How should I formulate the query correctly?
There may be another way to delete this CollectionTable data?

--------------------------------
更新:

当我使用时:
List<A> objectList = em.createQuery("from A_table").getResultList();
->我收到错误消息:
A_Table is not mapped [from A_Table].

when i used :
List<A> objectList = em.createQuery("from A_table").getResultList();
-> i got error :
A_Table is not mapped [from A_Table].

所以我决定保留原样:
List<A> objectList = query.getResultList().
但是，如果我尝试将其删除:

So I decided to leave this line as it was:
List<A> objectList = query.getResultList().
But then, if i try to delete it:

for (A a:objectList)
{
   if(....)
   {
     List<String> Mylist = a.getMyList();
      em.getTransaction().begin();
      em.remove(Mylist);
      em.getTransaction().commit();
   }
}

我收到错误消息:

org.hibernate.MappingException: Unknown entity: org.hibernate.collection.PersistentBag

所以我尝试添加"@IndexColumn注释:

    .....
    @ElementCollection
    @CollectionTable(name = "A_Table")
    @IndexColumn(name= "indx")
    private List<String> MyList;
    ...

现在我收到此错误:

org.hibernate.MappingException: Unknown entity: org.hibernate.collection.PersistentList

我应该怎么做?

非常感谢您！

推荐答案

首先，您必须从父表中恢复元素，即A:

First of all, you must recover elements from your parent table, i.e. A:

List<A> objectList = em.createQuery("from A").getResultList(); 
// It would be neccesary to cast the result list

有了结果列表后，您现在就可以访问辅助表，并随心所欲地处理这些数据:

Once you have your result list, you can access now to your secondary table and do with these data whatever you want:

objectList.getMyList().clear();
...

如果它对您不起作用，则可以使用CriteriaQuery:

If it doesn't work to you, you can use CriteriaQuery:

CriteriaBuilder criteriaBuilder = em.getCriteriaBuilder();
CriteriaQuery<A> criteriaQuery = criteriaBuilder.createQuery(A.class);
criteriaQuery.from(A.class);
Query query = em.createQuery(criteriaQuery);
List<A> objectList = query.getResultList();

我注意到您在@Entity批注中具有名称属性，您的映射表未命名为"A"，而是"A_table":

I have notice that you have a name attribute in your @Entity annotation, your mapping table is not named "A", but "A_table":

List<A> objectList = em.createQuery("from A_table").getResultList();

要删除元素，请尝试将其一一删除，而不要删除整个列表:

To delete elements, try deleting it one by one instead of deleting the entire list:

List<String> Mylist = a.getMyList();
em.getTransaction().begin();
for (String element:Mylist){
    em.remove(element);
}
em.getTransaction().commit();

---------------------------
解决方案在这里:
如何从组织中删除数据.hibernate.collection.PersistentBag? |休眠(Jpa)

---------------------------
The solution is here:
How to delete data from org.hibernate.collection.PersistentBag? | Hibernate (Jpa)

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