JPA不生成“on delete set null” FK限制 [英] JPA not generating "on delete set null" FK restrictions

问题描述

我有两个相关的类JPA注释。报警和状态。一个警报可以有一个状态。

我需要的是能够删除一个状态，并且将一个空值传播到处于该状态的警报被删除。

也就是说，我需要将外键定义为删除集合null 。

  @Entity 
 public class Alarm {
 @Id 
 @GeneratedValue（strategy = GenerationType.SEQUENCE，generator =序列）
 @SequenceGenerator（name =sequence，sequenceName =alarm_pk_seq）
 private Integer id; 
 
 @OneToOne（cascade = CascadeType.ALL）
 @JoinColumn（name =idStatus）
私有状态状态; 
 $ b $ //获取/设置
} 
 
 @实体
公共类状态{
 @Id 
 @Column（name =idStatus）
私人整数ID; 
 
私有字符串描述; 
 
 // get / set 
} 
  

示例： / b>

之前：

 状态
 ID描述
 1新增
 2已分配
 3已结算
 
警报
 id身份
 1 1 
 2 2 
 3 2 
  

之后（删除id = 2的状态）

  STATUS 
 id说明
 1新
 3已结算
 
警报
身份
 1 1 
 2 NULL 
 3 NULL 
  

我自动使用Hibernate和PostgreSQL从源代码生成数据库。我已经尝试过所有可能的CascadeType但没有成功。

代码中有什么错误吗？是否有可能用JPA做到这一点？

解决方案

只要添加使用Hibernate注释：

  @OnDelete（action = OnDeleteAction.CASCADE）
  

产生的外键为：ON UPDATE NO ACTION DELETE CASCADE;

但是没有动作= OnDeleteAction.SET_NULL

另外，如果可能，我不喜欢将代码绑定到Hibernate上（但是如果可以的话，我可以用它）。 >这个线程讨论它。我不能相信在JPA（或Hibernate扩展）中没有简单的方法来生成外键。

I have two related clases JPA-annotated. Alarm and Status. One Alarm can have one Status.

What I need is to be able to delete one Status and "propagate" a null value to the Alarms that are in that Status that has been deleted.

That is, I need the foreign key to be defined as "on delete set null".

@Entity
public class Alarm {
    @Id
    @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="sequence")
    @SequenceGenerator(name="sequence", sequenceName="alarm_pk_seq")
    private Integer id;

    @OneToOne(cascade=CascadeType.ALL)
    @JoinColumn(name="idStatus")
    private Status status;

    // get/set
}

@Entity
public class Status {
    @Id
    @Column(name="idStatus")
    private Integer id;

    private String description;

    // get/set
}

Example:

Before:

STATUS
id  description
1   new
2   assigned
3   closed

ALARMS
id  status
1   1
2   2
3   2

After (deleting the status with id=2)

STATUS
id  description
1   new
3   closed

ALARMS
id  status
1   1
2   NULL
3   NULL

I am using Hibernate and PostgreSQL, automatically generating the database from source code. I have tried with every possible CascadeType with no success.

Is there anything wrong in the code ? Is it possible to do it with JPA ?

解决方案

Just add that using the Hibernate annotation:

@OnDelete(action=OnDeleteAction.CASCADE)

generates the foreign key as : "ON UPDATE NO ACTION ON DELETE CASCADE;"

But there is no action=OnDeleteAction.SET_NULL

Moreover, I don't like to tie my code to Hibernate if possible (but I can live with it if it works).

This thread discusses it. I can't believe there is not an easy method in JPA (or Hibernate extensions) to generate the foreign key.

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