The Eocene framework is based on the front controller design pattern. Web application design methodologies can be categorized into front controller and page controller design patterns (as implemented in ASP.NET). In the front controller design pattern, a single controller (e.g. a Servlet in Java) handles all user requests. For an application of moderate complexity, a front controller delegates the responsibility to command controllers (also called dispatchers). In an Eocene-based system, all command classes are directly or indirectly derived from BaseCommand.
Figure 1 shows the class diagram of the front controller design pattern as used in the Eocene framework. Application developers write command classes (shown as ApplicationClass stereotypes). The framework provides the base command class and the front controller class. The front controller object is the only global variable and only the receiver has “freestanding” codes. A receiver receives a request from users and instantiates the front controller class to activate the framework. An application based on the Eocene framework may have one or more receivers, but there is only one front controller.
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