I have a composite/primary key composed of two attributes. One of the attributes is supposed to be only populated by a trigger (im using MySQL). Its not actually a sequence, but the function trigger takes care of supplying its values.
However, on the java side, since it is a primary key, it is supposed to be not nullable. So everytime I save an entity object, the application complains, saying it requires a value for one of the attribute that is auto-generated. Temporarily I have supplied an arbitrary value to the attribute, because eventually it will be overwritten by the trigger.