Special Edition Using Java™ 2 Enterprise Edition

Hybrid Architectures

You don't have to confine yourself to a single architecture for your entire application. Many applications use a mixture of two- and three-tiered designs. When you need to create a database maintenance application to modify the data used by your application, you can create a two-tiered application. The main application can still be three-tiered. You will often find that the amount of effort required to make a three-tiered database maintenance application is excessive, especially if your only goal is to use the same architecture for all parts of your application.

Likewise, you might have a two-tiered application that also needs to access some external data sources. You can create a component that accesses the external system ...