What is AOP

AOP, Aspect Oriented Programming, decomposes a system into concerns, instead of objects. AOP attempts to deal with "aspects" that cross-cut across the code of a system. This cross-cutting code can be difficult or impossible to modularize with OOP. The most common example of a cross-cutting concern is logging. Code for doing logging typically must be scattered all over a system. With AOP, you can declare, for example, that a system should write a log record at the beginning and end of all method invocations.

Probably the most popular framework for AOP is AspectJ. Alternatively, Spring provides AOP services that implement the AOP Alliance interfaces.