Part III. POMA and OSGi

OSGi is the dynamic module system for the Java platform. Part III provides a brief introduction to OSGi. Following this introduction, we’ll examine the loan sample we discussed in several of the pattern sample code sections throughout Part II. Specifically, we’ll begin with the final version of the Loan sample from the Colocate Exceptions sample code. In doing so, you should experience several of the benefits that runtime support for modularity provides, further entrenching the concepts discussed in Part I.

Part III is a departure from the higher-level concepts presented thus far and is the perfect companion to the earlier discussions in Parts I and II that demonstrate how the patterns can be applied using OSGi. Possibly more important, though, Part III demonstrates that by applying the patterns presented in Part II, it’s a technology exercise to bring the system under the control of OSGi. That is, once you’ve designed a modular software system, adopting a framework that supports and enforces modularity is much easier than if the system doesn’t have a modular architecture.