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From "Philip Miller" <philip.mil...@bbc.co.uk>
Subject RE: Selective commit
Date Mon, 07 Jan 2008 14:28:53 GMT
Nested data contexts may also help you to isolate atomic changes to the object graph. Especially
when the commitChangesLocally() method is implemented (nudge ;). Check out DataContext.createChildDataContext().

 

> -----Original Message-----
> From: Andrus Adamchik [mailto:andrus@objectstyle.org] 
> Sent: 07 January 2008 13:32
> To: user@cayenne.apache.org
> Subject: Re: Selective commit
> 
> Hi Álvaro,
> 
> It is hard to give a precise advice on multithreading without 
> knowing the nature of your application. So here is a few 
> general notes:
> 
> * DataContext instance is your isolated area for making 
> in-memory changes to objects that will all be committed at 
> once. So consider using multiple contexts as appropriate. 
> Cayenne docs recommend various common patterns, such as 
> DataContext per session (i.e. each user has a dedicated 
> context), DataContext per request, or DataContext per 
> application (in a read-only app). You can also devise your 
> own approach, if none of the above fit your needs. All you 
> need to know here is that multiple threads *reading* from a 
> shared DataContext is ok, but multiple threads *writing* to a 
> shared DataContext is not ok.
> 
> * In a rare case if you really need multiple threads to work 
> off of the same context, consider using a dedicated nested 
> DataContext for each atomic object modifications.
> 
> Andrus
> 
> 
> On Jan 7, 2008, at 2:44 PM, Álvaro Martínez wrote:
> >
> > Hi, I've been working for a while with Cayenne but never realized I 
> > had a problem... until I got a weird exception.
> >
> > The fact is that I had been using context.newObject() and
> > context.commitChanges() to create new rows in the database. But my 
> > application works with many threads, so global commits can (and in 
> > fact do) interrupt normal creation of objects. Thread A and 
> Thread B 
> > are creating objects and filling their fields, but then B 
> commits all 
> > and A throws a validation exception because mandatory fields are 
> > missing.
> >
> > How could I commit only one object?
> >
> > Thanks,
> >
> > Álvaro from Spain (Push the button Inc.)
> >
> >
> >
> 
> 

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