JPA协会没有外键 [英] JPA association without foreign key

问题描述

是否有可能在不使用JPA的情况下创建一个ManyToOne关联，并在数据库中创建一个外键？

这些表由另一个系统拥有，并被异步填充。因此我们在数据库中不能有FK。几乎总是有一个关系。

  @ManyToOne（fetch = FetchType.LAZY）
 @JoinColumns（ {
 @JoinColumn（name =`Order Type`，referencedColumnName =`Order Type`，insertable = false，updatable = false），
 @JoinColumn（name =`Order No` ，referenceColumnName =`No`，insertable = false，updatable = false）
}，foreignKey = @ javax.persistence.ForeignKey（value = ConstraintMode.NO_CONSTRAINT））
 Private OrderHeader orderHeader; 
  

问题在于JPA SchemaUpdate尝试添加FK，即使ConstraintMode.NO_CONSTRAINT

[错误] ohthSchemaUpdate - 无法添加外键约束

我们可以忽略它，如果它没有使其余的语句失败

[error] ohthSchemaUpdate - 语句关闭后不允许任何操作。

我们在hibernate-entitymanager 4.3.7.Final和JPA 2.1中。

解决方案

忽略ConstraintMode.NO_CONSTRAINT，看起来像是Hibernate 4中的一个bug，因为它被固定在5中。

https://hibernate.atlassian.net/browse/HHH-8805

一个d确实这篇文章在这里：

与单个映射表的多个关系，而不用Hibernate生成外键

建议添加已弃用的（hibernate而不是JPA） annotation

  @ForeignKey（name =none）
  

到关系应该有效。

Is it possible to set up a ManyToOne association without JPA creating a foreign key in the database?

The tables are owned by another system and are populated asynchronously. Thus we can't have a FK in the database. There's still, almost always, eventually a relation.

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumns({
        @JoinColumn(name="`Order Type`", referencedColumnName = "`Order Type`", insertable = false, updatable = false),
        @JoinColumn(name="`Order No`", referencedColumnName = "`No`", insertable = false, updatable = false)
}, foreignKey = @javax.persistence.ForeignKey(value = ConstraintMode.NO_CONSTRAINT))
private OrderHeader orderHeader;

The problem is that JPA SchemaUpdate tries to add a FK even though ConstraintMode.NO_CONSTRAINT

[error] o.h.t.h.SchemaUpdate - Cannot add foreign key constraint

and we could ignore that if it didn't make the rest of the statements fail

[error] o.h.t.h.SchemaUpdate - No operations allowed after statement closed.

We're on hibernate-entitymanager 4.3.7.Final and JPA 2.1.

解决方案

The fact that ConstraintMode.NO_CONSTRAINT is ignored looks like a bug in Hibernate 4 due to be fixed in 5.

https://hibernate.atlassian.net/browse/HHH-8805

The comments on that and indeed this post here:

Multiple relationships with single mapping table without generating foreign keys by Hibernate

suggest adding the deprecated (hibernate rather than JPA) annotation

@ForeignKey( name = "none" )

to the relationship should work.

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