ONJava.com: Aspect-Oriented Annotations: "Aspect-Oriented Annotations
by Bill Burke, coauthor of Enterprise JavaBeans, 4th Edition
Annotations are one of the new language features in J2SE 5.0, and allow you to attach metadata onto any Java construct. Meanwhile, Aspect-Oriented Programming (AOP) is a fairly new technology that makes it easier for you to encapsulate behavior that is usually messier, harder, or impossible to do with regular object-oriented (OO) techniques. Together, they make a new powerful combination that gives framework developers a more expressive way of providing their APIs. This article dives into combining these technologies using the JBoss AOP framework in various coding examples to show how you can use this combination to actually extend the Java language."