(+) Attitude Unlimited

Here is the summary of my presentation that I did earlier this evening at Kansas City Java User’s Group.

Aspect Oriented Programming & Aspect J 101

Agenda

• What is AOP?
• OOP and AOP
• Definitions, buzz words
• Aspect J
• Demo

Introduction

• Programming Methodologies: Past & Present
• Concerns: Core & secondary concerns
• Matching Concerns & Methodology: Flexiblility with Quality

Modularization

How to indentify non-modular systems?

• Code Tangling
• Code Scattering

AOP

• AOP allows us to dynamically modify our static model to include the code required to fulfill the secondary requirements without having to modify the original static model

Examples Of Aspects

• Development Aspects: Logging, Tracing, Debugging, Profiling, etc.,
• Production Aspects: Performance Monitoring, Notifications, Security, Error Handling

AOP Process

• Aspectual Decomposition: Identify core & cross cutting concerns
• Concern Implementation: Implement concerns independently
• Aspectual Recomposition: Create Aspects

Benefits of AOP

• Higher and cleaner level of modularization
• Easier System Evolution
• More code reuse

Buzz Words

• Crosscutting: Concerns spanning multiple modules. Static & Dynamic
• Join Point: A well-defined point in the program flow. Method, Constructor, Field Access, Exception Handler, Class Initialization, Object Initialization
• Pointcut: Collection of Join Points and values at those points
• Advice: Piece of code executed at a Join Point
• Introduction: Introducing change to static model
• Aspects: It consists of: Point Cuts, Join Point, Advice.
• Scattering: Similar code distributed throughout many files/programs
• Tangling: Two or more concerns implemented in the same body of code.
• Weaving: Compile time Weaving & Runtime Weaving

Pointcuts

• Definition: Collection of Join Points and values at those points
• Example: [accessspecifier] pointcut pointcutname([args]) : pointcut-definition

Advice

• Definition: Piece of code executed at a Join Point
• Types: before, after and around.

Java Implementation of AOP
There were two prominent schools of thoughts.

• AspectJ: a general-purpose aspect-oriented extension to Java
• AspectWerkz: Simple, high-performant, dynamic, lightweight and powerful AOP for Java

AspectJ is

• a seamless aspect-oriented extension to the Java programming language
• Java platform compatible
• easy to learn and use

AspectJ enables

• clean modularization of crosscutting concerns, such as error checking and handling, synchronization, context-sensitive behavior, performance optimizations, monitoring and logging, debugging support, and multi-object protocols

References:

• AspectJ at Eclipse: http://eclipse.org/aspectj/
• Aspectwertz: http://aspectwerkz.codehaus.org/