Enterprise JavaBeans, Fourth Edition

Dependent Value Classes

Dependent value classes are custom serializable objects that can be used as persistence fields (although this use is not recommended). They are useful for packaging data and moving it between an entity bean and its remote clients. They separate the client’s view of the entity bean from its abstract persistence model, which makes it easier for the entity bean class to change without affecting existing clients.

The remote interface methods of an entity bean should be defined independently of the abstract persistence schema. In other words, you should design the remote interfaces to model the business concepts, not the underlying persistence programming model. Dependent value classes can help separate a remote client’s view from the persistence model by providing objects that fill the gaps in these perspectives.

For example, the CustomerEJB could be modified so that its lastName and firstName fields are not exposed to remote clients through their accessor methods. This is a reasonable design approach, since most clients access the entire name of the customer at once. The remote interface might be modified to look like:

import java.rmi.RemoteException;

public interface CustomerRemote extends javax.ejb.EJBObject {
       
    public Name getName( ) throws RemoteException;
    public void setName(Name name) throws RemoteException;
    
}

This remote interface is simpler than the one we saw earlier. It allows the remote client to get all the name information in one method call instead ...