@ManyToOne of the same type as parent where child doesn't exist in DB

Question

I used Spring Roo to reverse engineer a MySQL database, a db to which I only have read access.

One of the entities called Transaction has a field called originalTransaction, in the DB this is set that it can be null, but that the default value is 0.

@RooJavaBean
@RooToString
@SuppressWarnings("serial")
@RooDbManaged(automaticallyDelete = true)
@RooJpaActiveRecord(versionField = "", table = "TRANSACTIONS")
public class Transaction implements Serializable {

    ....

    @Fetch(value = FetchMode.SELECT)
    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name = "ORIG_TRANS_ID")
    private Transaction originalTransaction;

    ....

}

FetchMode.Select and FetchType.Lazy I added as workarounds for other problems.

Now when I insert a transaction and I leave originalTransaction null, the DB changes it to 0.

When I do an entity().find(12345678), I get the following error:

Unable to find Transaction with id 0

javax.persistence.EntityNotFoundException: Unable to find Transaction with id 0
        at org.hibernate.ejb.Ejb3Configuration$Ejb3EntityNotFoundDelegate.handleEntityNotFound(Ejb3Configuration.java:157)
        at org.hibernate.proxy.AbstractLazyInitializer.checkTargetState(AbstractLazyInitializer.java:261)
        at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:175)
        at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:285)    

So obviously (which wasn't so obvious initially), it's trying to find the originalTransaction and since the DB changes the null to 0, it's trying to find Transaction with id=0 which doesn't exist - this causes entity.find(12345678) to return null even though the transaction is in the database.

Is there any workaround to stop Hibernate / JPA from bailing the search and returning null if the originalTransaction's id in the DB doesn't exist? I'd preferably force it to null if it doesn't exist.

Answer 1

If you use Hibernate you can try

@NotFound(action = NotFoundAction.IGNORE)

Otherwise you have to clean up your database (0 is not null). If there is no parent, the ORIG_TRANS_ID should be null