Hi all,
i'm just in the process of creating a web application bound to cayenne
in the backend. I'm using external transactions (XA with multiple
databases) and basically start/commit/rollback a transaction whenever i
have something to change inside the databases. While this is working
fine i'm trying to understand the way cayenne behaves regarding the
object context lifecycle.
Imagine the following use case:
startTX();
List<Object> objects = querySomeObjectsViaTheObjectContext();
commitTX(); or rollbackTX();
If i understand correctly relationships are not necessary resolved
directly but lazy when accessed through an object. My question now is
how does the object context behave when it has to fetch some additional
objects due to relationships that have to be resolved on access? I mean
obviously the object context is no longer valid (?) as potentially the
external transaction manager might have closed it's correspodning
datasource and returned it back to the connection pool.
However the objects in my list are still available in memory and can be
used although cannot be modified easily or be committed in the next
transaction as they of course don't belong to the newly created object
context.
So what i'm doing right now (and i'm sure i'm missing some important
facsts as this is a really hack solution) is to create a new
transaction, requery all the objects i modified and transfer all
modified attributes to the ones i just got back from the query.
I'd really appreciate some explanation on how you guys approach stuff
like, i mean it's obvious that i have to store the objects in a user
interface (showing them in a table or whatever) but cannot keep and
transaction ongoing as long as the user interface is waiting for some
interaction.
Cheers,
Daniel
