On Jan 22, 2007, at 4:48 AM, Aristedes Maniatis wrote:
>
> On 22/01/2007, at 10:47 PM, Andrus Adamchik (JIRA) wrote:
>
>> JPA specification supports a notion of "embeddable" class.
>> Embeddable classes can be viewed as multi-column custom types that
>> do not have their own identity and belong to another persistent
>> object. Entities that embed them can override DB column mapping.
>> Currently Cayenne supports single-column custom types via
>> ExtendedType mechanism. We need to expand that to support multi-
>> column Embeddables and mapping via the Modeler.
>
> When would you use such a thing? I am trying to think of how this
> is useful, but perhaps I'm missing the point of the concept. Would
> this be used to create a type of inheritance between classes, such
> as company and person having a common billing address class but
> relating back to completely separate address fields in each of the
> company and person tables in the db?
The simple case is the Address class that is contained in multiple
classes, e.g.
class Employee {
Address homeAddress;
Address workAddress;
...
}
class Business {
Address primaryAddress;
...
}
The EMPLOYEE table contains columns HOME_STREET, HOME_CITY,
HOME_STATE, HOME_ZIP, HOME_COUNTRY, WORK_STREET, WORK_CITY,
WORK_STATE, WORK_ZIP, WORK_COUNTRY. The BUSINESS table contains
columns PRIMARY_STREET, PRIMARY_CITY, PRIMARY_STATE, PRIMARY_ZIP,
PRIMARY_COUNTRY.
There is no separate Address table and no Address instance that
exists outside the "owning" Employee or Business instance.
Craig
>
> Also, is it a goal to make 3.0 fully JPA compliant or is that too
> ambitious in the timeframe (I'm guessing a reasonable target for
> 3.0 would be some time in 6-9 months).
>
> Ari Maniatis
>
>
> -------------------------->
> ish
> http://www.ish.com.au
> Level 1, 30 Wilson Street Newtown 2042 Australia
> phone +61 2 9550 5001 fax +61 2 9550 4001
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>
>
Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:Craig.Russel..un.com
P.S. A good JDO? O, Gasp!
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