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.)
