Another way you could look at is that by using things like customerId and accountId as your database primary keys you're mixing your business stuff with the database persistence stuff. If you create a primary key in the base class and call it something like id, you can still have the accountId and customerId in the subclasses. But ignore that database primary key (id) in your business logic and only use it for database things. You still have and can still use customerId and accountId in queries. Think of the database primary key, id, as just some book keeping stuff, an implementation detail, for the orm (datanucleus).
Yegor wrote: > Thanks for your reply. I guess that's what I will do in my next app. > However, in the existing app the identity fields are already defined > in the subclasses, and they have different names too, e.g. Account > would have accountId, Customer would have customerId, so I cannot move > the ID field to the root of the hierarchy as it will not map to the > existing data in the App Engine Datastore. > > This seems very strange. Ability to move common fields into a shared > class seems like a very natural thing to do. I am surprised that it is > not supported by Datanucleus. > > That said, I haven't lost all hope. Maybe composition instead of > inheritance can help. I am going to check if I can use embedded > classes to solve this problem. > > Yegor > > On Dec 13, 1:54 am, datanucleus <[email protected]> wrote: >> With all persistence standards, the identity field(s)/property(s) have >> to be in the base persistent class. > > -- > > You received this message because you are subscribed to the Google Groups > "Google App Engine for Java" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/google-appengine-java?hl=en. > > -- You received this message because you are subscribed to the Google Groups "Google App Engine for Java" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/google-appengine-java?hl=en.
