ParaAJ: Toward reusable and maintainable Aspect Oriented Programs

Aspect Oriented Programming (AOP) aims to ease maintenance and promote reuse of software components by separating core concerns from crosscutting concerns: aspects of a program that cannot be confined to a single program component. In AOP languages such as AspectJ, this kind of concern is encapsulated in an aspect and connected to main classes using pointcuts. This removes extraneous code from the classes of the program, allowing them to focus on their core purpose and making them more maintainable and reusable. The implementation of each crosscutting concern, which would have been scattered throughout an object oriented program, is centralised in a single aspect. Unfortunately, due to the way aspects and classes are associated, and the lack of an explicit interface between them, these aspects may be tightly coupled to the classes of the program and so may not be as reusable or maintainable as might be expected. We propose ParaAJ (Parametric Aspects), as an extension to AspectJ. ParaAJ allows classes to specify which aspects should be applied, and allows applications to specify which aspects to apply to which classes in what ways. This makes it easier for classes and aspects to be developed and maintained independently, and encourages reuse of both.