Struts is the premier framework for building Java-based Web applications. Using the Model-View-Controller (MVC) design pattern, Struts solves many of the problems associated with developing high-performance, business-oriented Web applications that use Java servlets and JavaServer Pages. At the outset, it is important to understand that Struts is more than just a programming convenience. Struts has fundamentally reshaped the way that Web programmers think about and
structure a Web application. It is a technology that no Web programmer can afford to ignore.
When Sun introduced JSP technology, it provided a development road map for working with it and defined two models for building JSP-based Web applications. The two models are known as Model 1 and Model 2 and they prescribe different approaches to designing JSP-based Web applications. Model 1, the simpler of the two, was the primary solution implemented when JSPs were first introduced. However, over time, Model 2 has been accepted as the best way for building JSP-based Web applications and, as you’ll see, is the inspiration for MVC-based Web frameworks like Struts. Following
is an overview of both architectures.
A request is made to a JSP or servlet and then that JSP or servlet handles all responsibilities for the request, including processing the request, validating data, handling the business logic, and generating a response. Although conceptually
simple, this architecture is not conducive to large-scale application development because, inevitably, a great deal of functionality is duplicated in each JSP. Also, the Model 1 architecture unnecessarily ties together the business logic and presentation logic of the application. Combining business logic with presentation logic makes it hard to introduce a new ‘view’ or access point in an application. For example, in addition to an HTML interface, you might want to include a Wireless Markup Language (WML) interface for wireless access. In this case, using Model 1 will unnecessarily require the duplication of the business logic with each instance of the presentation code.
Model 2, or as it is most commonly referred to today, Model-View-Controller (MVC), solves many of the inherent problems with the original Model 1 design by providing a clear separation of application responsibilities. In the MVC architecture, a central servlet, known as the Controller, receives all requests for the application. The Controller then processes the request and works with the Model to prepare any data needed by the View (which is usually a JSP) and forwards the data to a JSP. The JSP then uses the data prepared by the Controller to generate a response to the browser. In this
architecture, the business and presentation logic are separated from each other. Having the separation of business and presentation code accommodates multiple interfaces to the application, be they Web, wireless, or GUI (Swing). Additionally, this separation provides excellent reuse of code.