AspectJ

AspectJ is an aspect-oriented extension to the Java programming language created at Xerox PARC. An AspectJ compiler weaves aspects into Java bytecode to implement crosscutting concerns. Aspects are written in a combination of Java and AspectJ and are woven on a incremental per-class basis into Java (source or .class files) to produce standard Java bytecodes (making Java and AspectJ compatible). There are at least two compilers for the AspectJ language, ajc which is part of the toolset supported by the AspectJ eclipse project, and which is an extensible optimizing compiler provided at aspectbench.org.