cayenne-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Durchholz, Joachim" <Joachim.Durchh...@hennig-fahrzeugteile.de>
Subject RE: Standalone app, Threads and Object contexts
Date Wed, 02 May 2012 13:46:23 GMT
> I got the impression that there was some sort of connection
> pooling built-in to Cayenne because in the Modeller there
> is a setting for minimum and maximum connections.  Now I'm
> getting confused and perhaps I'm using incorrect terminology.

As I said, I'm still stuck with Hibernate, so I'm quite fuzzy about exact details here.
However, I think it is entirely possible that Cayenne already has some built-in connection
pooling. In a J2SE context, it would essentially just be a connection recreator.

> In my mind there is the actual connection to the database
> as defined during the creation of the DataContext.

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 ;-) )

Mime
View raw message