One to many foreign key on non-primary key

frer · **Joined:** Wed Jul 14, 2004 11:51 am **Posts:** 43

Hello,

I have to map my hibernate classes to an existing db and am having the following problem:

I have ClassA which has a one-to-many relationship with ClassB. However the foreign key is not done with the primary key of class A.

The data model would look like this

Code:

Table A
---------
field1 (primary key)
field2

Table B
---------
field3 (primary key)
field4

In Table B, field 4 is a foreign key to field2 (I know this is a bad practice for it should be mapped to field1 but as I said it is an existing database).

Therefore, what I am trying to do is set the correct hibernate mapping to be able to specify the property (or field) of the foreign key (which is not the primary key). I saw that this is possible for a many-to-one relationship with the attribute property-ref:

Code:

<many-to-one
        name="propertyName"                                (1)
        column="column_name"                               (2)
        class="ClassName"                                  (3)
        cascade="all|none|save-update|delete"              (4)
        outer-join="true|false|auto"                       (5)
        update="true|false"                                (6)
        insert="true|false"                                (6)
        property-ref="propertyNameFromAssociatedClass"     (7)
        access="field|property|ClassName"                  (8)
/>

Unfortunately, I can't find the equivalent for a Set and a one-to-many collection.

Anybody have an idea how I could do this (if I can) or if this is a know feature upcoming?

Thanks,

Francois

emmanuel · **Posted:** Tue Jul 27, 2004 12:19 pm

You can't and I don't thnk we'll support such features in the future

frer · **Joined:** Wed Jul 14, 2004 11:51 am **Posts:** 43

Hmmm.... I can understand that it might not be implemented yet but I found it weird for it not to be in future plans. I understand that it is a bad practice to map a foreign key on a non-primary key but unfortunately many legacy sytems use such associations. Therefore to be able to map hibernate on these entities it is necessary to have this.

Anyway, if I have a little time, I might try to work on it myself.

Thanks for your reply,

Fran

emmanuel · **Posted:** Fri Jul 30, 2004 9:53 am

Atually if you have such issues in you relational model, this probably means that you DB model will be quite hard to use with an ORM (other mistakes etc...)

skjhibern8 · **Joined:** Thu Nov 04, 2004 1:37 pm **Posts:** 10

this seems odd to me. i realize it is not normal to form a relationship on something other than the primary key, but it is common and often people will form relationships on alternate or unique keys.

sniper · **Joined:** Mon Jan 03, 2005 5:21 am **Posts:** 2

I find it bit odd tooo. In fact I'm facing the same problem which I have posted little earlier today.

[url]
http://forum.hibernate.org/viewtopic.php?t=937533
[/url]