I have wasted a lot of time trying to get this mapping to work. Perhaps you can help:





I have tried mapping each class (CashPayment,CheckPayment and CreditCardPayment) as its own class (not seen here) and then joining them to the Order object using:


Hibernate complains that the Payment class is not mapped. I thought this would work because it used implicit polymorphism. No Dice. Every other type of mapping requires some sort of discriminator. This is a "legacy" schema and I don't have the option to change it. There has got to be a way to map these tables as a collection.

Any ideas?

Regards,

Josh

I am using Hibernate 3.x and Oracle 9.x

Yeah the problem is that table-per-concrete-class doesn't mix with polymorphic assoiations well. It's a little ugly but here's one way you could approach it... the Order class could have three collections: one of each of the concrete payment classes. This could be hidden from users of Order (by using private accessor methods), and exposed using public accessor methods that deal with all the payments together by encapsulating access to each of the sub-collections.

E.g.

public Collection getPayments() {
Set payments = new HashSet();
payments.addAll(cashPayments);
payments.addAll(checkPayments);
payments.addAll(creditCardPayments);
return payments
}

public void addPayment(Payment payment) {
if(payment instanceof CashPayment) {
cashPayments.add(payment);
} else if (payment instanceof CheckPayment) {
checkPayments.add(payment);
} else if (payment instanceof CreditCardPayment) {
creditCardPayments.add(payment);
}
}
}

public void setPayments(Collection payments) {
for(Payment payment : payments) {
addPayment(payment);
}
}

I thought about doing something like that. The only problem I see is this:

Collection payments = order.getPayments();
payments.add(someNewPayment);

I think this would produce a hard to find bug. The only solution I can think of is to return a unmodifiable collection to force people to use the order.addPayment() method.

Any other ideas?