JSP Application Design with MVC

JSP Application Design with MVC

MVC was first described by Xerox in a number of papers published in the late 1980s. The key point of using MVC is to separate logic into three distinct units: the Model, the View, and the Controller. In a server application, we commonly classify the parts of the application as business logic, presentation, and request processing. Business logic is the term used for the manipulation of an application's data, such as customer, product, and order information. Presentation refers to how the application data is displayed to the user, for example, position, font, and size. And finally, request processing is what ties the business logic and presentation parts together. In MVC terms, the Model corresponds to business logic and data, the View to the presentation, and the Controller to the request processing.

An application data structure and logic (the Model) is typically the most stable part of an application, while the presentation of that data (the View) changes fairly often. Just look at all the face-lifts many web sites go through to keep up with the latest fashion in web design. Yet, the data they present remains the same. Another common example of why presentation should be separated from the business logic is that you may want to present the data in different languages or present different subsets of the data to internal and external users. Access to the data through new types of devices, such as cell phones and personal digital assistants (PDAs), is the latest trend. Each client type requires its own presentation format. It should come as no surprise, then, that separating business logic from the presentation makes it easier to evolve an application as the requirements change; new presentation interfaces can be developed without touching the business logic.