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 d...@cowlark.com wrote:
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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.
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