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Features Class Example Conclusion
Terminology Concerns Examples
An Overview of Aspect-Oriented Programming
Presented by
Jarrell W. Waggoner
College of Engineering and Computing
University of South Carolina
Features Class Example Conclusion
Terminology Concerns Examples
Terminology of Aspect-Oriented Programming (AOP)
Term: Concern
Definition: A feature or essential operation that is part of a
larger program or solution
Features Class Example Conclusion
Terminology Concerns Examples
Terminology of Aspect-Oriented Programming (AOP)
Term: Concern
Definition: A feature or essential operation that is part of a
larger program or solution
Term: Code Entanglement
Definition: Code that cannot be separated into more than one
concern
Term: Cross-Cutting Concern
Definition: A concern that is entangled with one or more other
concerns
Features Class Example Conclusion
Terminology Concerns Examples
Division of Concerns
How concerns are divided in different paradigms:
Functional Programming ⇒ Functions
Object-Oriented Programming ⇒ Objects
Functions: Code separation
Objects: Concern separation
Features Class Example Conclusion
Terminology Concerns Examples
Cross-Cutting Concern Examples
List of cross-cutting concerns:
System logging and tracing
Error handling
Statistics gathering
Security handling
Managed garbage collection
Features Class Example Conclusion
Terminology Concerns Examples
Cross-Cutting Concern Examples
List of cross-cutting concerns:
System logging and tracing
Error handling
Statistics gathering
Security handling
Managed garbage collection
Most OOP languages are extended to support Aspect-Orientation
rather than creating entirely new languages:
Common Lisp ⇒ AspectL
Java ⇒ AspectJ
C#/VB.Net ⇒ Aspect.NET
C/C++ ⇒ AspectC/Aspect C++
Features Class Example Conclusion
Properties Examples
Aspects
Aspect-Oriented Programming Languages:
Are fully object-oriented
Add the “aspects” construct
Aspects:
Encapsulate cross-cutting concerns that cannot be captured
by traditional objects
Generically applied to multiple objects
No direct modification to the objects themselves
Applied to all the objects in a program, or just a single object
Can add methods, or run code around existing methods
Can implement the methods defined by an interface (instead
of requiring an implementing object to do this)
Features Class Example Conclusion
Properties Examples
www.volantec.biz/Untangle AOP.ppt
Features Class Example Conclusion
Traversing Trees Diagram
Tree Traversal
Options for traversing a tree with varying types of nodes:
“Traditional” OO approach
“Functional” approach
Visitor approach
Aspect oriented approach
Note: Traversing our AST is a cross-cutting concern!
Anything besides Aspect-Oriented Programming is going to require
redundant code, clumsy “hacks” or special patterns that “abuse”
features of object-orientation.
Features Class Example Conclusion
Traversing Trees Diagram
Tree Traversal
Options for traversing a tree with varying types of nodes:
“Traditional” OO approach
“Functional” approach
Visitor approach
Aspect oriented approach
Note: Traversing our AST is a cross-cutting concern!
Anything besides Aspect-Oriented Programming is going to require
redundant code, clumsy “hacks” or special patterns that “abuse”
features of object-orientation.
Features Class Example Conclusion
Traversing Trees Diagram
Tree Traversal (cont.)
Anything besides Aspect-Oriented Programming is going to require
redundant code, clumsy “hacks” or special patterns that “abuse”
features of object-orientation.
Example
The visitor pattern uses (and some would argue abuses) the
polymorphic features of object-oriented languages to reduce the
code that is required to be part of a collection of objects. Every
object still has to have a minimal visit() method, however.
Aspect-Orientation will eliminate the need to ever touch the
original objects. No need for a visit() method!
Features Class Example Conclusion
Traversing Trees Diagram
Visitor Pattern with AOP
Implementing the Visitor Pattern with AspectJ:
Example
aspect VisitAspect {
void IfCommand.acceptVisitor(Visitor v) {
v.visit(this);
Features Class Example Conclusion
Traversing Trees Diagram
Diagram 1
AST
= visit() method
Features Class Example Conclusion
Traversing Trees Diagram
Diagram 2
AST
= visit() method
