Creating ToOne relationships that do not use the Primary Key Columns

Hi there is there a reason why Hibernate restricts you to use the target table’s ID column/s when creating a one-to-one or many-to-one relationship?

In my case I’ve got an existing legacy database, which does not have foreign keys defined and due to impacts on other legacy applications I cannot have them created due to impacts.

Now let’s say I’ve got a table called Owners, which has a primary key that is made up of:

  • name

  • surname

  • social_security_number

But this table also has a unique constraint that is made up of:

  • owner_id_number

Now I have another table called Vehicles that has an owner_id_number column (but is not defined as a foreign key of the other table) and I’d like to define a Many-To-One relationship using this column, as I know that I will have uniqueness due to the unique constraint in the Owners table, but when I do so I get the following error because I’m not using the Owners entity ID columns in the JoinColumn annotation reference.

Caused by: org.hibernate.AnnotationException: referencedColumnName(OWNER_ID_NUMBER) of referencing not mapped to a single property

I also confirm that OWNER_ID_NUMBER is defined as a unique constraint in the Owners entity using the table level constraint UniqueConstraint annotation.

Is there a way to achieve what I need given the limitations of my legacy database?

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You should be able to define the target join column with the annotation @JoinColumn(name = "owner_id_number", referencedColumnName = "owner_id_number") on the @ManyToOne annotated property.