hi armin,
i'm very interested in safe repository modifications because i need
implementing prefetched relationships.
during prefetch i disable cascadeRetrieve, this might cause side effects in
other threads reading the same relationship.
just my 0.02 chf
jakob
----- Original Message -----
From: "Armin Waibel" <[EMAIL PROTECTED]>
To: "OJB Users List" <[EMAIL PROTECTED]>
Sent: Friday, November 22, 2002 4:21 PM
Subject: Re: Modifying ClassDescriptor
> Hi Graham,
>
> ----- Original Message -----
> From: "Graham Lounder" <[EMAIL PROTECTED]>
> To: "OJB Users List" <[EMAIL PROTECTED]>
> Sent: Friday, November 22, 2002 3:17 PM
> Subject: Modifying ClassDescriptor
>
>
> > I'm fairly new to This API and I have some questions regarding the
> > ClassDescriptor.
> >
> > I'll first describe what I'm trying to achive ( if it's even possible
> to do
> > this)
> >
> > I've setup my repository_user.xml file to do cascade_delete = true for
> most
> > objects, but sometimes the user of the application may not want to
> cascade
> > delete. I added a boolean variable to my methods to check if the user
> wants
> > to cascade delete or not. If the user doesn't want to cascade delete,
> I was
> > pulling out the ClassDescriptor object from the instance of the broker
> and
> > modifying the ObjectReferenceDescriptors and the CollectionDescriptors
> to
> > cascade-delete=false. Now once my operation is complete, I noticed
> that the
> > broker kept the modifications. I tried to get a copy of the original
> > ClassDescriptor to reset it on the broker before closing it but failed
> this
> > attempt.
> >
> > I'm not really sure at this point how the ClassDescriptor information
> is
> > stored in memory.
>
> A few days ago, Thomas and I discuss (offline) the theme
> "runtime repository changes" with the result that we have to do
> a re-organistation of the repository stuff. We want to make it possible
> to select between a 'perThread' and a 'global' modification of the
> DescriptorRepository/ClassDescriptor/...
> Any comments are welcome.
>
> Currently each PBKey has a associated DescriptorRepository. All PB
> with the same PBKey share the same DescriptorRepository. Thus if you
> modify a ClassDescriptor, the changes take effect over all PB instances
> with
> the same PBKey, no good when run in multi-threaded environment.
>
> A quick and dirty solution of your problem could be:
> Add public method
> DescriptorRepository#readFromRepository(PBKey pbKey)
> This method returns a copy of the repository.
> Extent PersistenceBrokerImpl and add method
> setRepository(DescriptorRepository repository)
> {
> this.descriptorRepository = repository;
> }
> Now you are able to change the repository of a single PB instance.
> Get a copy, set the copy, modify the copy, do your work,
> restore the old repository reference (for better performance: undo
> modification on copy, keep copy in memory).
>
> HTH
>
> I could add a public
> DescriptorRepository#readFromRepository(PBKey pbKey)
> method to CVS if you think this could be useful for you.
>
> regards,
> Armin
>
> > I also tried for fun to create another instance of the
> > broker inside this method and pull the ClassDescriptor as well to see
> if it
> > would be modified when I modified the other one and in deed it is
> being
> > modified. This seems to tell me that all the brokers shared the safe
> > reference to the ClassDescription object representing the mapping of
> the xml
> > file.
> >
> > I was able to reload the file and get the original version and set it
> on the
> > broker once I finished my operation. But wouldn't this also modify
> any
> > other broker in progress and hence not give the user the results he is
> > looking for in the end.
> >
> > I would really appreciate any help or information concerning this
> issue.
> >
> > Thanks
> >
> > ============================================
> > Graham Lounder
> > Java Developer
> > Spatial Components Division
> > CARIS
> > 264 Rookwood Ave
> > Fredericton NB E3B-2M2
> > Office 506 462-4263
> > Fax 506 459-3849
> > [EMAIL PROTECTED]
> > http://www.spatialcomponents.com
> > ============================================
> >
> >
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> >
>
>
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