On 05/02/2012 09:46 AM, Durchholz, Joachim wrote:
No, a DataContext is a context within which retrieving the same rows
via some query will always give you identical Java objects. That's a
pretty powerful (and important) property, but not necessarily related
to a connection. (Connections become important as soon as you need
transaction-related guarantees.) You don't need to create an
ObjectContext to work with a DataContext - any DataContext already is
an ObjectContext. You don't roll back a database transaction here, you
roll back to whatever was last loaded from the database. If you use
child contexts, you can roll back to whatever the state was when that
child context was started. I believe that this means that you may have
data loaded in different transactions in your application, and that
that is the price you pay for getting rid of
LazyInitializationExceptions. (True Cayenne experts, please correct if
that's wrong. I'm writing this both to help Andrew along and to get
helped along ;-) )
One thing I found that I must create at least one ObjectContextChild
before the DataContext becomes usable otherwise I'm not seeing the
connection being made to the database in the log files. I'm using
Cayenne 3.0.2 and an Oracle database. I can provide a log trace if
required.
