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From Andrew Willerding <awillerd...@itsurcom.com>
Subject Re: Standalone app, Threads and Object contexts
Date Wed, 02 May 2012 15:43:59 GMT
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.



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