Hibernate Cascade PERSIST [英] Hibernate Cascade PERSIST

问题描述

我有A类和B类，其中B依赖于A

我有一个关于Hibernate的常见问题，

在我的代码中，当我调用em.persist（objOfTypeA）时，我期望插入并插入到表AAA和BBB中。如果我手动设置A获得A的ID并将其填充到每个对象的列表中，然后保留该列表，那么事情就会起作用。
但是我希望Hibernate会发生这种情况。

我做错了什么？
或者我只是期望太多的Hibernate？

谢谢

  @Entity 
 @Table（name =AAA）
 @Veto 
 public class A {
 
 @Id 
 @GeneratedValue 
 @Column（name =Id）
私人长ID; 
 
 
 @NotNull 
 @Column（name =Name）
私人长名称; 
 
 ... 
 
 @OneToMany（mappedBy =a，fetch = FetchType.LAZY，cascade = {CascadeType.PERSIST，CascadeType.MERGE，CascadeType.REMOVE}） 
私人列表< B> b; 
 ... 
} 
 
 @Entity 
 @Table（name =BBB）
 @Veto 
 public class B {
 
 @Id 
 @GeneratedValue 
 @Column（name =Id）
私人长ID; 
 
 @NotNull 
 @Column（name =AId）
 private长aId; 
 
 @NotNull 
 @Column（name =Name）
私人长名称; 
 
 @JoinColumn（name =AId，referencedColumnName =Id，updatable = false，insertable = false）
 @ManyToOne（可选= false）
 private A a; 
 ... 
} 
  

解决方案

我终于搞定了。
我得到或发现的例子都没有告诉我究竟出了什么问题，只是在我自己的实验之后才设法得出这个结论：

而不是

  @OneToMany（mappedBy =a，fetch = FetchType.LAZY，cascade = {CascadeType.PERSIST， CascadeType.MERGE，CascadeType.REMOVE}）
私人列表< B> b; 
  

不起作用（FK仍然是NULL）

这确实奏效：

  @OneToMany（fetch = FetchType.LAZY，cascade = {CascadeType.PERSIST ，CascadeType.MERGE，CascadeType.REMOVE}）
 @JoinColumn（name =AId）
 @NotNull 
 private List< B> b; 
  

I have a general question about Hibernate that I'm batteling with.

I have class A and class B, where B is dependent on A

In my code when I call em.persist(objOfTypeA) I would expect the insert to go and insert into both tables AAA and BBB. If I manually presist A get A's ID and fill it in the list for each object and then persist that list, things are working. But I would expect this to happen magically by Hibernate.

Am I doing something wrong? Or am I just expecting too much of Hibernate?

Thanks

@Entity
@Table(name = "AAA")
@Veto
public class A {

    @Id
    @GeneratedValue
    @Column(name = "Id")
    private Long id;


    @NotNull
    @Column(name = "Name")
    private Long name;

    ...

    @OneToMany(mappedBy="a", fetch=FetchType.LAZY, cascade={CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REMOVE})
    private List<B> b;
...
}

@Entity
@Table(name = "BBB")
@Veto
public class B {

    @Id
    @GeneratedValue
    @Column(name="Id")
    private Long id;

    @NotNull
    @Column(name="AId")
    private Long aId;

    @NotNull
    @Column(name = "Name")
    private Long name;

    @JoinColumn(name = "AId", referencedColumnName="Id", updatable = false, insertable = false)
    @ManyToOne(optional = false)
    private A a;
...     
}

解决方案

I finally worked it out. None of the examples I was given or found told me exactly what was wrong, it was only after my own experimentation that I managed to come to this conclusion:

Instead of having

@OneToMany(mappedBy="a", fetch=FetchType.LAZY, cascade={CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REMOVE})
private List<B> b;

that didn't work (FK was still coming as NULL)

This did work:

@OneToMany(fetch=FetchType.LAZY, cascade={CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REMOVE})
@JoinColumn(name="AId")
@NotNull
private List<B> b;

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