Does anyone know if JPA supports polymorphism? I've been working with JDO because it appears to be better documented right now, but I'd switch for a more Java-like model. Tom
On Sun, Aug 23, 2009 at 7:22 AM, David Given <[email protected]> wrote: > > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > jd wrote: > [...] > > I have a structure similar to this this: > [...] > > class Zoo > > class Zebra implements Animal > > class Donkey implements Animal > [...] > > javax.jdo.JDOUserException: Field "animal" is declared as a reference > > type (interface/Object) but no implementation classes of "Animal" have > > been found! > > JDO on App Engine doesn't support polymorphism, as I understand it, > which means you have to store your Zebras and Donkeys separately. I take > it that what you want is a mixed bag of Animals of differing objects? > > The only way I found of doing that was to manually serialise my objects > and store them in Blobs. It's not as hard as it looks, as the low-level > API is quite nicely designed, but you do need to explicitly pull fields > you want indexed out of the object before serialisation and store them > as indexable properties on the entity. > > - -- > ┌─── ｄｇ＠ｃｏｗｌａｒｋ．ｃｏｍ ───── http://www.cowlark.com ───── > │ > │ "People who think they know everything really annoy those of us who > │ know we don't." --- Bjarne Stroustrup > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.9 (GNU/Linux) > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ > > iD8DBQFKkVCdf9E0noFvlzgRAmmBAJwIHs8T5Qy5t0FgQ/ik4oTdOca1rACg0Oy1 > IzwfB2MUttjgJZMdgAetr38= > =U8uT > -----END PGP SIGNATURE----- > > > > --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
