This paper presents JAC (Java Aspect Components), a framework for aspect-oriented programming in Java.Unlike languages such as AspectJ which are mostly class-based,JAC is object-based and does not require any language extensions to Java.It uses the Javassist class load-time MOP.An aspect program in JAC is a set of aspect objects that can be dynamically deploted and undeployed on top on running application objects.Aspect objects may define three kinds of aspect methods: wrapping mwthods (that wrap application methods and provide the ability to run code before and after the wrapped methods), role methods (that add new funchtionalities to applications objects) and exception handlers.The aspects composition issue is handled through a well defined wrapping controller that specifies for each wrapped object at wrap-time, runtime or both, the execusion order of aspect objects.