A More Generalized Upgrade Approach
In Figure 4, I present a more general approach to the upgrade problem. You can see that I’ve added a new element in the center of the network, called a software factory. This is an entity that could be designed to generate upgrades on demand.
The software factory could be designated as the location where the Digester runs. So the output of the factory could be complete upgrades such as the one required by our old friend the HR director.
The key point is that the Commons Digester framework provides a really useful scheme for unmarshalling Java classes based on XML rules.
Figure 4 A software factory to dispense upgrades