Java™ Data Objects

5.6. Inheritance

JDO’s support for implementation and inheritance hierarchies is a major benefit of the technology. It enables the design of domain object models that closely represent the business domain.

The support for inheritance is particularly flexible. A class might be persistence-capable even if its superclass is not. Equally, that class’s subclasses may be persistence-capable or not as required by the developer. Thus, in an inheritance hierarchy, classes may be independently persistence-capable and non-persistence-capable.

When one class in an inheritance hierarchy is defined as persistence-capable in a persistence descriptor, the persistence modifiers ascribed to its fields (per sistent, transactional or none) are inherited by subclasses. ...