In the nearest future we'll be adding a "merge" method to the
DataContext that would do exactly what you described here - reattach
an already persistent and possibly modified object to the context. For
now the closest analog is "localObject", but it will require some
hacking. A reattach method may look like this:
void reattach(Persistent object) {
// force "modified" on the object
object.setPersistenceState(PersistenceState.MODIFIED);
context.localObject(object.getObjectId(), object);
}
This will do the right thing for objects not changed, but WILL NOT do
the right thing for the newly inserted objects.
Andrus
On Nov 29, 2007, at 1:33 PM, Detlef Burt wrote:
Hello,
after being able to keep my Data after sending my Objects via JMS
(Thanks Andrus) I now have a problem when I try to write the Objects
back into the Database.
After sending the Objects to the Client-Application, the Client
changes some data ( Just a timestamp in my Testcase ) and then sends
an Update-Request to the Server. Due to the fact, that the Client
has no access to the DataContext or the underlying ObjectStore, the
changes made to the Object won't be recorded.
After the Server receives the Object, it reconnects the Object to
the DataContext, thus being able to get a snapshot from the database
or even create an UpdateQuery.
But I can't go anywhere from here.
Executing the UpdateQuery won't have any effect because Cayenne
doesn't know what changed.
I also tried to get a Snapshot from the DB, convert my DataObject to
a DataRow and then create and register the diff of those by myself.
But I couldn't find anything like that :/
To sum it all up:
- Can I tell Cayenne to replace the Database Contents with the data
from my Object while retaining the ObjectId ?
- Can I tell Cayenne to "scan" an Object for changes and register
the differences, so that calling commitChanges will update the Object?
- Or is it possible to create a DataRow from a DataObject so I can
create and register an ObjectDiff ?
NOTE:
When updating the Object, I don't know what class is being updated
and what properties it has, all I have is my
CayennePersistableObject Baseclass, which extends CayenneDataObject.
Detlef
