Summary

This chapter presented a case study on using the Theme approach for a software-usage licensing system. As we did in the previous chapter, we used an abbreviated Theme/Doc approach in which no individual theme views were used. That choice was made because the requirements were few enough that we could keep in mind what the structure of the themes should be without needing additional reminders or clues.

We then walked through designing the two-part system. The first part covered the functionality set out by the first use case (refer to Figure 9-1) and comprised three base themes (usage registration, application registration, and download), which were composed together. The second part addressed the second use case (refer to Figure 9-2) in which purchasers use the application they downloaded. Usage was allowed depending on the license model selected at the time of downloading. Three themes would be involved in any composition of this part of the system: the enforce theme, the launch theme (which runs the application), and the chosen license model theme. The enforce theme was designed to crosscut the license model theme, which in turn crosscuts the launch theme.

Finally, we went over some code examples of how to implement the second use case in AspectJ. Rather than using abstract aspects, as discussed in Chapter 7, we chose to fuse the implementation of the bind relationship with the template parameters found in the Theme/UML model.