Just one more comment. The fact that a PersistenceCapable should use
datastore identity is orthogonal to whether it contains a field that
can uniquely identify the instance. It is considered best practice in
some circles to use a surrogate key for identifying instances in the
datastore regardless of whether there is a field that is unique. So I
don't see the need for arbitrarily restricting the use case simply
because there is no persistent identity for the key instances.
Craig
On Nov 21, 2005, at 2:43 PM, Craig L Russell wrote:
Hi Abe,
On Nov 21, 2005, at 12:59 PM, Abe White wrote:
The issue came up with the TCK where we were trying to get JPOX
to recognize that an embedded PersistenceCapable in a join table
can have a unique identifying field. In the case of datastore
identity, this doesn't work because there is no primary key field
in the PersistenceCapable.
<proposed 18.14>
A portable mapping for arrays, collections, and maps will include
a primary key on the join table.
</proposed 18.14>
Why? I don't understand this at all. "Datastore identity" is
meaningless in this context, as embedded objects have no identity
according to the spec.
Right. They have no persistent identity. Therefore, if you want to
use an embedded PersistenceCapable as a key, you need to identify
one of the embedded fields as a key for the purpose of the map. The
alternative is to simply disallow using an embedded
PersistenceCapable as a key in a map if the class is defined as
datastore identity. But this seems pretty arbitrary.
Craig
Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:[EMAIL PROTECTED]
P.S. A good JDO? O, Gasp!
Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:[EMAIL PROTECTED]
P.S. A good JDO? O, Gasp!
