ASPECT ORIENTED SOFTWARE DEVELOPMENT

1
ASPECT ORIENTEDSOFTWARE DEVELOPMENT

• Prepared By Ebru Dogan

2
Presentation Outline

• Current Methods and Languages
• Separation of Concerns (SOC)
• Problem cross-cutting
• Concepts of Aspect-Oriented Development
• Aspect Oriented Programming (AOP)
• Applications Tracer example
• Integration Aspects and Components
• Conclusions
• References

3
Current Methods and Languages

• Support abstraction mechanisms for breaking a
  system down into components
• Concentrate on finding and composing functional
  units

4
Benefits of Good Modularity

• Also known as clean separation of concerns
• no scattered code
• no tangling
• highly cohesive loosely coupled

5
Separation of Concerns - Cohesion

• Cohesive component performs only one concern/task

6
Separation of Concerns - Coupling

• Two components are independent if they do not
  have interactions
• Highly coupled components have many
  dependencies/interactions

7
Modularity is not always possible...

• Some concerns dont localize to objects
• their code tends to be orthogonal to the rest
  of the requirements
• and is spread out through many modules

8
Examples of crosscutting concerns

• Synchronization
• Real-time constraints
• Error-checking
• Object interaction constraints
• Memory management
• Persistency
• Security
• Caching
• Logging
• Monitoring
• Testing
• Domain specific optimization
• ...

9
Example - Figure Editor - Design
10
Figure Editor Example contd
11
Crosscutting Concern - Example
12
Aspect-oriented development

• Aspect-oriented development addresses separation
  of concerns (SOC)
• Concerns are associated with cross-cutting
• Cross-cutting concerns are implemented as aspects
  and are dynamically woven into a program

13
Motivation for Aspect-Oriented Programming

• Programming paradigm for encapsulating
  crosscutting concerns into aspects.
• AOP builds on top of other programming paradigms
  object-oriented, procedural or functional. It
  does not supplant them.

14
Key Abstractions for Different Programming
Paradigms
Paradigm Abstraction Modularization
Structured programming control flow control structure
Procedural programming computations procedure
Object-oriented programming data types class/object
Aspect-Oriented programming crosscutting concerns aspect
15
Concepts of AOP (I)

• Aspect unit encapsulating a crosscutting
  concern.
• Join point point in the execution of a program
  where an aspect might intervene.
• ... whenever condition C arises, perform
  action A
• Pointcutexpression of a subset of join points
  (condition C)
• Advice piece of code for action A.
• Pointcuts and advice encapsulated into aspects.

16
Concepts of AOP (II)

• Weaving

17
Few Examples of Existing AOP technologies

• AspectJ
• HyperJ
• AspectC
• Aspect
• Caesar
• CompositionFilters
• AspectWerkz
• JBoss-AOP

18
Most Popular AOP technology

• AspectJ
• a general purpose AO programming language
• just as Java is a general-purpose OO language
• extension to Java

19
AspectJ

• Five simple steps to create an AOP
• Define the core/base functionality classes
• Define the aspect class
• Define the pointcut
• Declare the advice
• Weave Compile

20
Tracer Example Without AOP
21
Tracer Example With AOP
22
Advantages of AOP

• Improves performance
• Allows better code reuse
• Enables better code encapsulation

23
Componentizing Aspects

• Representing each aspect as a single reusable
  component
• Map the characteristics of a component on aspect
• Explore the applicability of concepts on aspect

24
Conclusions

• Crosscutting concerns are typically scattered
  over several modules and result in tangled code.
• This reduces the modularity and as such the
  quality of the software system.
• AOSD provides explicit abstractions mechanisms to
  represent these so-called aspects and compose
  these into programs.
• Increases the modularity of systems.

25
References

• http//www.aosd.net/
• http//www.eclipse.org/aspectj/
• http//en.wikipedia.org/wiki/Aspect-oriented_progr
  amming
• http//csl.ensm-douai.fr/fakih/phd
• Fil05 Aspect-Oriented Software Development by
  R.Filman et al., ISBN 0321219767