How to specify FK that is not PK of other table

johnsmitty · **Joined:** Sun Jan 15, 2006 12:28 am **Posts:** 4

I can't figure out how to do something.

I have one table named "authority" that has Id, username, and privilege.

I have another table named "user_account" that has Id, and username.

I want to be able to just add Authority objects to the UserAccount object and have it persisted in these tables.

How do I configure Authority.hbm.xml so that the "username" property is of class "UserAccount" but doesn't use the "Id" in the relationship, but "username" instead? That is, how can I map one object to another, and use something other than the Id as the foreign key?

"Authority" is the only object that uses "username" as the foreign key. All the other objects use the "Id" of UserAccount. So I don't want to change UserAccount to use "username" as its primary key.

I am stumped.

ReneStolp · **Posted:** Sun Jan 15, 2006 9:28 am

Hi!

You can have foreign key references not only to primary keys but to any UNIQUE, NOT NULL column in another table (this is not a Hibernate restriction, but a general database modelling issue).

Why don't you change your mapping an a way that user_account.id is referenced from authority? One could even think to extract the mapping into a seperate mapping table to allow the same privilege to be shared by several users.

If you want to stay with your mapping, did you have a look at the where="arbitrary sql where condition" property of a mapping (see section 6.2 in the reference manual)?

All the best,

René

zzyborg · **Posted:** Tue Jan 17, 2006 5:26 am

you may use the "property-ref" attribute to point to a field other than primary key
hope this will help u :)

johnsmitty · **Joined:** Sun Jan 15, 2006 12:28 am **Posts:** 4

In Authority.hbm.xml I have this:

Code:

<many-to-one name="userAccount" column="username" class="UserAccount" not-null="true" property-ref="username" />

and in UserAccount.hbm.xml I have this:

Code:

<set name="authoritySet" inverse="true" cascade="all">
            <key column="username" property-ref="username"/>
            <one-to-many class="Authority"/>
        </set>

In UserAccount.java I added this:

Code:

private java.util.Set authoritySet = new HashSet();
public void addAuthority(Authority authority) {
       getAuthoritySet().add(authority);
    }

and in the code where I use all this, I do this:

Code:

Authority authority = new Authority();
authority.setUserAccount(newUserAccount);
newUserAccount.addAuthority(authority);

Thanks you guys's help.

johnsmitty · **Joined:** Sun Jan 15, 2006 12:28 am **Posts:** 4

....But now I found a new problem. Whenever I try to "saveOrUpdate" the UserAccount, I get an error:

Code:

java.lang.NullPointerException
        at org.hibernate.engine.EntityEntry.getLoadedValue(EntityEntry.java:177)

        at org.hibernate.type.CollectionType.getKeyOfOwner(CollectionType.java:3
04)
        at org.hibernate.engine.Collections.processReachableCollection(Collectio
ns.java:173)
        at org.hibernate.event.def.FlushVisitor.processCollection(FlushVisitor.j
ava:37)

If I remove the mapping in UserAccount.hbm.xml of the Authority set, then the update works just fine for the UserAccount. Yikes. I don't get this at all. Any help would be very much appreciated. I am using hibernate 3.1.2 btw

johnsmitty · **Joined:** Sun Jan 15, 2006 12:28 am **Posts:** 4

It looks like the second problem I ran into is a bug in hibernate. I changed some hibernate code according to the fixes listed in this thread and it works now:
http://opensource2.atlassian.com/projec ... se/HB-1526