Refactoring the Aspectizable Interfaces: An Empirical Assessment

1
Refactoring the Aspectizable Interfaces An
Empirical Assessment

• Presenter Patrick Joyce
• Authors Paolo Tonella and Mariano Ceccato
• IEEE Transactions, Software Engineering, October
  2005

2
Overview

• What is Aspect-Oriented Programming (AOP)?
• Concepts
• Terminology
• What are Aspectizable Interfaces?
• How can we benefit from this design?
• Maintainability
• Understandability
• Size Reduction
• Modularity

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Aspect-Oriented Programming

• Goal Separate orthogonal and principle concerns
• Benefits
• Collect scattered code into one maintainable
  unit
• No original source code required to add/remove
  aspects
• Example class BarChart
• Principle Concerns
• LoadChart()
• DisplayChart()
• SaveChart()
• Orthogonal Concern
• Logging

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Aspect-Oriented Programming

• Aspect
• Primary modularization unit
• Represents an orthogonal concern
• Joinpoint
• A specific area of execution in an application
• E.g., object instantiation, method call, variable
  declaration, etc.
• Pointcut
• A collection of joinpoints specifies where the
  concern applies
• E.g., (AspectJ) - pointcut callSetMethods()
  call(void set(..))
• Advice
• The implementation of the aspects defines how
  and where to implements the concern
• Weaving
• The process of combining the aspect code with the
  original application

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Aspectizable Interfaces

• Interface Roles
• Collect abstract properties of the principal
  concern of the class
• Collect transversal properties that crosscut the
  principal concern of the class
• Non-Aspectizable Interfaces
• Adhere to the first role
• Example Collection
• Aspectizable Interfaces
• Adhere to the second role
• Examples Serializable, Observable (note
  normally end with able)

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Refactoring Aspectizable Interfaces

• Move interface properties to aspect
• Attributes
• Methods
• Inner Classes
• UNPLUG
• Input A.java, I.java
• Output A.java, IA.aj

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Refactoring Example Observable

• See Eclipse Project

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Refactoring Analysis

• Hypotheses
• AOP code for aspectizable interfaces
• Is easier to maintain.
• Is easier to understand.
• Is significantly smaller in size.
• Improves modularity.
• Application
• Refactor a large proportion of the standard Java
  library
• Refactor three open source programs
• Analysis Methods
• (1,2) Empirical Maintenance Study
• (3,4) Customized Metrics (UCLOC, OP, OCOH, ACOH,
  ICOUPL)

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Refactoring Results

• Class cohesion increased
• Extracted methods are loosely connection with
  other class operations
• Interface coupling decreased
• Size remained untouched
• Understandability increased
• Maintainability remained similar
• Possibly due to the relative size

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Conclusion

• Questions?