Re: AW: Delete object in a 1:N assoc only with RemovalAwareCollection?

[Armin Waibel]

Hi Rainer,

Rainer Klute wrote:


this is good news! However, I need something working the next days that supports circular
references and lets modifications of persistent objects to be ignored if 
these objects are
not locked in a ODMG transaction.

"something working the next days", puh!
This is exactly what we want for 1.1. We have to introduce a real 
two-level cache.
On first level we temporary buffer objects to resolve circular 
references, on second level we cache copies of objects without their 
references. This is nothing to make work in a few days ;-)
In CVS you can find a ObjectCache (alpha-)implementation by Oliver Matz 
called TwoLevelCache which try to bypass current cache problems (but 
cause new problems).

Do you have an idea to do this right? Presently I am thinking about copying a whole graph
of persistent objects to an equivalent graph of non-persistent ones. The 
latter I can modify
at will without consequences to the database or to the cache. However, 
if I decide to persist
them I have a) to delete the object tree from the DB (and from the 
cache) and b) make my
non-persistent tree persistent. This is one big hack with all sorts of 
pitfalls and I'd
like to know if there's a better approach.

hmm, you can use non-distributed ObjectCache implementation, e.g. 
ObjectCachePerBrokerImpl. This supports circular references and avoid 
concurrent object modification by other threads/broker instances.
But you will loose all cached objects when broker was closed/rolled back.
Nevertheless, if you have a fast DB and a fast network between OJB and 
DB this should be ok.

Or before start to modify make a deep copy of the object (e.g. introduce 
a CopyFactory or something similar), then lock the copy and start to modify.

regards,
Armin
Best regard
Rainer Klute
                           Rainer Klute IT-Consulting GmbH
  Dipl.-Inform.
  Rainer Klute             E-Mail:  [EMAIL PROTECTED]
  K�rner Grund 24          Telefon: +49 172 2324824
D-44143 Dortmund           Telefax: +49 231 5349423
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