Special Edition Using Java™ 2 Enterprise Edition

The Three Layers of an Application

No matter how you slice it, a typical application consists of three layers:

• The data layer manages the data used by the application. An application that stores its data in data files is said to implement the data layer itself. Many applications use a database to manage the storage of the data. The database itself is considered the data layer for the application.

• The business logic layer contains the various business rules and operations that the application performs on its data. When you store an order, the data section stores the various parts of the order, whereas the business logic section calculates the price of the order, handles any credit card validation, and verifies that the order has all the required ...