Hibernate级联：对象引用未保存的瞬态实例 - 在刷新之前保存瞬态实例 [英] Hibernate cascades : Object references an unsaved transient instance - save the transient instance before flushing

问题描述

  @Entity 
 @Table（name =parent）
 public final class Parent extends Base {
 
 @OneToOne（cascade = CascadeType.PERSIST，fetch = FetchType.EAGER）
 private person person; 
  

以及（除其他外）：

 父亲=新父（）; 
 Person person = new Person（）; 
 parent.setPerson（person）; 
 session.save（parent）; 
  

我得到上述异常？

我是否需要手动调用session.save（person）？我必须添加级联类型注释到childs类定义（它引用父级）？

或者我错过了其他明显的东西？

我不希望将CascadeType.ALL用作父母被删除时我想保留此人（孩子）。

两个实体/表扩展了一个通用基表：

  @MappedSuperclass（）
 public abstract class Base {
 
 @Id 
 @GeneratedValue（strategy = GenerationType.AUTO）
 private Integer id; 
 
 public Integer getId（）{
 return id; 
} 
  

这会影响到哪种级联类型？

解决方案

您还没有提到Hibernate版本，但自从我开始使用它之后，这一点并没有改变。

正如你可以阅读 Hibernate reference ，以获得Java标准 SAVE_UPDATE ，您需要 {CascadeType.PERSIST，CascadeType.MERGE} 在Hibernate中。

编辑：看到更新的信息，你现在正在做的事情导致Hibernate把它当作双向的一对一映射。这基本上意味着对于这两个表中的任何一个中的每个对象，必须是另一个表中具有相同ID的对象。因此，您不能只删除其中的一个，否则您将失去FK完整性。

如果您希望它是单向映射，例如，如果您希望能够删除该人但离开父母 - 必须通过 @JoinColumn 来指定FK，例如
@JoinColumn（name = PERSON_ID，unique = false，nullable = true，insertable = true，updatable = true）

@Entity
@Table(name = "parent")
public final class Parent extends Base {

@OneToOne(cascade = CascadeType.PERSIST, fetch = FetchType.EAGER)
private Person person;

and doing (amongst other things) this :

Parent parent = new Parent();
Person person = new Person();
parent.setPerson(person);
session.save(parent);

I get the mentioned exception ?

Do I manually need to call session.save(person) before ? do I have to add a cascade type annotation to the childs class definition(where it references the parent) ?

Or have I missed something else obvious ?

I don't want to use CascadeType.ALL as when a parent is deleted I want to keep the person(child).

Both entities/tables extend a common Base table :

@MappedSuperclass()
public abstract class Base {

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

    public Integer getId() {
    return id;
    }

Will this effect which cascade type is required ?

解决方案

You haven't mentioned the Hibernate version, but this hasn't changed since I ever started using it.

As you can read in the Hibernate reference, to get the Java standard SAVE_UPDATE you need {CascadeType.PERSIST, CascadeType.MERGE} in Hibernate.

EDIT: Seeing the updated info, what you're doing now causes Hibernate to treat it as a bi-directional one-to-one mapping. This basically means that for each object in any of those two tables, there has got to be a counterpart in the other table with the same ID. Therefore, you cannot delete only one of them, you would lose FK integrity.

If you want it to be a unidirectional mapping, e.g., if you want to be able to delete the person but leave the parent -- you have to specify a FK, usually via @JoinColumn, like @JoinColumn(name="PERSON_ID", unique=false, nullable=true, insertable=true, updatable=true)

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