Hibernate is not updating 'DiscriminatorColumn' on 'InheritanceType.SINGLE_TABLE' inheritance.

In the case you change the type of the class (mutate the object class -> recreate a new class). The discriminator column in not updated.

Is there a workaround using the annotations.

We found one workaround changing the persister update statement :

final SingleTableEntityPersister persister = (SingleTableEntityPersister) sess.getEntityPersister(null, anObjectOfClassA );
//
// Use reflection to access that method..
final Method getSQLUpdateStrings = AbstractEntityPersister.class.getDeclaredMethod("getSQLUpdateStrings");
getSQLUpdateStrings.setAccessible(true);
//
// Add the discriminator at the beginning of the request.
final String[] updates = (String[]) getSQLUpdateStrings.invoke(persister);
updates[0] = updates[0].replace("update CLASS_A_TABLE set", "update CLASS_A_TABLE set CLASS_A_TABLE_KIND='TERM', ");

You will have to explain me how you mutate a class from one type to another in Java or any OO language, it's just magic :)