Option 3?
There is also a dataContext.unregisterObjects() call which supposedly
sets the collection of objects you pass in (your random cars) to a
TRANSIENT state, which might be better than setting them directly on the
object (in case the data context does some other stuff behind the
scenes).
/dev/mrg
-----Original Message-----
From: Gentry, Michael
Sent: Wednesday, June 30, 2004 12:46 PM
To: Elia Morling; cayenne-use..bjectstyle.org
Subject: RE: Working with Transient Objects
OK, two suggestions to try (since you obviously have a better test
environment for this than me).
1) Use transient variables like I suggested. Just keep the persistent
cars separate from the random cars. The persistent cars are obviously
in a data context, the random ones created outside of one (this might
not be possible, but I'd hope so).
public List allCars()
{
List results = new List();
results.addAll(savedCars());
results.addAll(randomCars());
return results;
}
(Add all the other plumbing you need to create the random cars, etc.)
2) Cheat.
import org.objectstyle.cayenne.PersistenceState;
randomCar.setPersistenceState(COMMITTED); // Make it think it's already
saved
Or, have you tried this one?
randomCar.setPersistenceState(TRANSIENT);
Let us know if either of these approaches work for you.
Thanks,
/dev/mrg
-----Original Message-----
From: Elia Morling [mailto:eli..amiljen.se]
Sent: Wednesday, June 30, 2004 12:34 PM
To: cayenne-use..bjectstyle.org
Subject: Re: Working with Transient Objects
Sorry, let me try to make a better example.
In the Cayenne Modeler I have a Car and a ParkingLot. In my
database I have stored 1 ParkingLot and 5 Car(s).
Now, I fire up my game. I get the ParkingLot and 5 Car(s) all stored
in the database. Now I want 5 randomly created computer-controlled
Car(s) for the duration of the game only. I want to use all the fields
in
my Car class as they are identical, except that I don't want to store
them in the database. Why? Because the next time I start the game I
want to randomly create 5 new ones. Meanwhile I want to commit any
changes made to the 5 Car(s) controlled by players. All I need is
a PersistenceState flag like NEW_DONT_COMMIT or similar on
the computer controlled Car(s) so that the DataContext doesn't store
them in the database.
Elia
----- Original Message -----
From: "Gentry, Michael" <michael_gentr..anniemae.com>
To: "Elia Morling" <eli..amiljen.se>; <cayenne-user@objectstyle.org>
Sent: Wednesday, June 30, 2004 6:05 PM
Subject: RE: Working with Transient Objects
I'm not sure if I understand what you are trying to do, but ...
You have two entities which you modeled in Cayenne Modeler, Car and
ParkingLot. You want to persist the ParkingLot entities, but not the
Car entities? Do you ever persist Car entities? It doesn't sound to me
like you want to persist them.
If you do not want to persist the Car, you shouldn't be modeling it in
Cayenne Modeler at all. What you should do is model the ParkingLot
entity and in the subclass of the ParkingLot class (where you add your
business logic), create your own setters, getters, and transient
instance variables. Something similar to this:
public class ParkingLot extends _ParkingLot
{
private List cars;
public void addToCarArray(Car car)
{
if (cars == null)
cars = new List();
cars.add(car);
}
public void removeFromCarArray(Car car)
{
if (cars != null)
cars.remove(car);
}
public List cars()
{
if (cars == null)
cars = new List();
return cars;
}
}
NOTE: I didn't try to compile any of the above, but the general idea is
to handle transient information in the subclass. You don't model
transient information in Cayenne Modeler (the Car -- make plain old java
class for it). It's also a good idea to use the subclass to handle
derived information, possibly even caching it for efficiency (if it
makes sense to do so -- you have to be careful if the parent values
change, which would change the derived value). For example, you could
have a fullName() method which returns firstName() + " " + middleName()
+ " " + lastName(). And, of course, any convenience methods go in the
subclass, too.
Hope that helps!
/dev/mrg
-----Original Message-----
From: Elia Morling [mailto:eli..amiljen.se]
Sent: Tuesday, June 29, 2004 5:21 PM
To: cayenne-use..bjectstyle.org
Subject: Working with Transient Objects
Hi,
Here's an example to illustrate my problem. I have a parking lot
with 5 cars stored in the database. Every time I start up my
application I need to create 5 new cars for the duration of the
run only. I don't want to store them in the database so I simply
create the objects without a context using regular new().
Now I can't make them work with the parking lot, when using:
parkinglot.addToCarArray(car);
OR
car.setParkinglot(parkinglot)
Why doesn't this work and what should I do about it? I need to
have database cars and non-database cars to co-exist in the
parkinglot.
Elia
This archive was generated by hypermail 2.0.0 : Wed Jun 30 2004 - 12:51:22 EDT