Is it possible to change a discriminator value for a persisted object? I have designed tree using the composit pattern with the thee classes element, leaf and node. Leaf and node are subclasses of element. My problem is, I have to put a new leaf on an persisted leaf, so this leaf have to become a node with the same Id, because other object references to it. Creating a new node with the same attibutes as the leaf updates all attibutes except for the discriminator.
How can I solve this problem?

Many thanks in advance.
katie

Use direct JDBC. Objects cannot "change classes" in Java.