英文:
Hibernate Onetomany self join adds unique constraint
问题
@Entity
public class Layer {
@Id
private Long id;
@Column(name = "PARENT_ID")
private String parentId;
@OneToMany
@JoinColumn(name = "PARENT_ID", referencedColumnName = "PARENT_ID", updatable = false, insertable = false, foreignKey = @ForeignKey(ConstraintMode.NO_CONSTRAINT))
private Set
}
This means that I want to get all the other entities sharing the same 'parentId'. The reason I want it is because it would be easier to write queries for this entity.
The problem is that on database generation ('spring.jpa.properties.hibernate.hbm2ddl.auto=create'), it also adds a unique constraint on the 'PARENT_ID' column, and I do not want that.
How do I keep Hibernate from adding the unique constraint?
英文:
I would like to add a one to many relationship of an entity with itself:
@Entity
public class Layer {
@Id
private Long id;
@Column(name = "PARENT_ID")
private String parentId;
@OneToMany
@JoinColumn(name = "PARENT_ID", referencedColumnName = "PARENT_ID", updatable = false, insertable = false, foreignKey = @ForeignKey(ConstraintMode.NO_CONSTRAINT))
private Set<Layer> siblings;
}
This means that I want to get all the other entities sharing the same parentId. The reason I want it is because it would be easier to write queries for this entity.
The problem is that on database generation(spring.jpa.properties.hibernate.hbm2ddl.auto=create) it also adds a unique constraint on the PARENT_ID column and I do not want that.
How do I keep hibernate from adding the unique constraint?
答案1
得分: 0
你的映射目前使得 children 通过列 PARENT_ID 引用它们的父级。为了将某个内容用作引用，它必须是唯一的。
你可能希望将子级通过其 id 引用其父级。
以下代码可以实现这个目标：
@OneToMany
@JoinColumn(name = "PARENT_ID", referencedColumnName = "ID", updatable = false, insertable = false, foreignKey = @ForeignKey(ConstraintMode.NO_CONSTRAINT))
private Set<Layer> children;
我不确定你是否还可以有一个 String parentId。首先，它映射到与 children 属性相同的列，但类型不同：id 的类型是 Long，而应引用它的 parentId 的类型是 String。
正常的做法是创建一个属性 Layer parent，并使用 @ManyToOne 和 mappedBy 与 children 关联。
英文:
Your mapping currently makes children reference their parent by the column PARENT_ID. In order to use something as a reference it has to be unique.
What you probably want to have is the children to reference their parent by its id.
This should do the trick:
@OneToMany
@JoinColumn(name = "PARENT_ID", referencedColumnName = "ID", updatable = false, insertable = false, foreignKey = @ForeignKey(ConstraintMode.NO_CONSTRAINT))
private Set<Layer> children;
I'm not sure that you can have a String parentId as well.
First it maps to the same column as the children property, but with a different type: id is of type Long, while parentId which should reference it is of type String.
The normal way to do this would be to make a property Layer parent which @ManyToOne and mappedBy children.
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