The Current System

The current system's source can be found in your team's directory on Dogbert, in the implicitinvocation directory. It is decomposed into the following modules:

• Registrar This component listens for requests to register students and registers them. If the requested section is full, the registrar announces OverfullEvent and does not register them for the class; if an error occurs while attempting to register the student, an ExceptionEvent will be announced indicating that the registration did no

  This component also listens for requests to cancel a student's registration. If the student was not registered in the class, a NotRegisteredException will be announced; otherwise, the registration will be attempted. If the registration fails, the exception received by the Registrar will be announced as an ExceptionEvent.

• FeedbackUI This component listens for events which the user needs to be notified of, and delivers the information to the user of the system. It announces nothing, and subscribes to all ExceptionEvents.

The following events are available in the provided system:

• ExceptionEvent This event takes the place of normal exceptions; when exceptions are caught from invoking methods, this event is announced. The only component which subscribes to this in the given system is the FeedbackUI which displays the error to the user.

  One result of the current implementation is that any component which subscribes to ExceptionEvent will also hear all subclasses of the Exception class when any are announced. As a result, when the FeedbackUI subscribes to all ExceptionEvents, it also hears the NotRegisteredException when it is announced.

• NotRegisteredException This event indicates that someone asked to be removed from a section they were not registered for.

• NotFullEvent (*) This event is announced whenever cancellation of a registration causes a section to drop from ``full'' to having an open registration space.

• OverfullEvent (*) This event is announced when a student attempts to register in a full section. The registration does not take place when this event is announced.

• RegisterStudentEvent This event is announced to indicate that a specific student wishes to register in a specific section of a class. The Registrar will hear this event and react as outlined in the description of the Registrar above.

• UnRegisterStudentEvent This event is announced to indicate that a specific student should be removed from registration in a specific section of a class. The Registrar will hear this event and react as outlined in the description of the Registrar above.

The events marked (*) are currently announced, but no component subscribes to them. As such, data may be added to these events to carry additional information if necessary; the unmarked events may not be changed.

In addition, the following module will create the event bindings and activate the user interface:

• CreateBindings This module will create the event bindings and activate the user interface.

As usual, the adapter serves to connect the user interface to the implementation. For this system, the adapter translates user interface requests into event announcements.

To complete your solution, you should only add or modify event registrations to the modules above, add any necessary new modules, and make changes to CreateBindings to use the new modules. You may change the data associated with the events marked (*) above, but may not change when they are announced by existing components. Do not make any other changes to the provided modules