In a multi-tier environment (eg. eCommerce development environment), the deployed web applications are separated into three different physical layers:
- Presentation Layer;
- Controller Layer;
- Data Layer.
Of this three, the most complex layer is the “Controller Layer” which contains all of our business logic. In an eCommerce application the controller will have multiple levels composed of servlets, java server pages (JSPs) and enterprise JavaBeans (POJO). Therefore, in this type of architecture will be no overlapping between the different tier boundaries. For example, a java servlet will not contain any presentation logic, nor a java server page (JSP) will not contains any business logic.
That’s why in the multi-tier architecture, the application will generally perform better and faster and provide greater flexibility.