EJB.B.2 Inheritance

The current EJB specification does not specify the concept of component inheritance . There are complex issues that would have to be addressed in order to define component inheritance (for example, the issue of how the primary key of the derived class relates to the primary key of the parent class, and how component inheritance affects the parent component's persistence).

However, the bean provider can take advantage of the Java programming language support for inheritance as follows :

• Interface inheritance . It is possible to use the Java programming language interface inheritance mechanism for inheritance of the home and remote interfaces. A component may derive its home and remote interfaces from some "parent" home and remote interfaces; the component then can be used anywhere where a component with the parent interfaces is expected. This is a Java language feature, and its use is transparent to the EJB container.

• Implementation class inheritance . It is possible to take advantage of the Java class implementation inheritance mechanism for the enterprise bean class. For example, the class CheckingAccountBean class can extend the AccountBean class to inherit the implementation of the business methods .