AW: [Objectbridge-developers] Automated deletion of depending obj ects

[Mahler T. <tho...@it...>]

Hi Rainer,

> -----Urspr=FCngliche Nachricht-----
> Von: Bischof, Rainer [mailto:rai...@ed...]
> Gesendet: Dienstag, 25. September 2001 16:53
> An: 'obj...@li...'
> Betreff: [Objectbridge-developers] Automated deletion of depending
> objects
> Wichtigkeit: Hoch
>=20
>=20
> Hi Thomas,
>=20
> somewhere I have read that OJB supports automated deletion of=20
> depending
> objects in a 1-m relationship. The question is: how do I do that?
>=20
> I have an object which contains a Vector of depending=20
> objects. I want to
> delete one of these. So I just open a transaction, get a=20
> handle to the main
> object and remove one of the depending objects from the Vector. On
> transaction submit I would expect that OJB removes the=20
> corresponding row in
> the table.
>=20
> This does not happen for me ;-(
> Mapping has "true" entries for automated retrieval, update=20
> and delete. Do I
> need to use an ODMG collection instead of the Vector?
>=20

Yes, you need object level transactions that come only with ODMG !

See excerpt from the FAQ:

Say you use the PB to query an object O that has a collection attribute =
col
with five elements a,b,c,d,e. Next you delete Objects d and e from col =
and
store O again with PersistenceBroker.store(O);
PB will store the remaining objects a,b,c. But it will NOT delete d and =
e !
If you then requery object O it will again contain a,b,c,d,e !!!=20
The PB keeps no transactional state of the persistent Objects, thus it =
does
not know that d and e have to be deleted. (as a side note: deletion of =
d and
e could also be an error, as there might be references to them from =
other
objects !!!)
Using ODMG for the above scenario will eliminate all trouble: Objects =
are
registered to a transaction so that on commit of the transaction it =
knows
that d and e do not longer belong to the collection. the ODMG =
collection
will not delete the objects d and e but only the REFERENCES from the
collection to those objects!


> Thanks
> Rainer
>=20
>=20
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>=20