An Aspect-Aware Outline Viewer

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An Aspect-Aware Outline Viewer

• Michihiro Horie and Shigeru Chiba
• Tokyo Institute of Technology, Japan

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Our purpose

• Problem difficulty to understand relationships
  between programs and aspects
• Obliviousness aspects and classes separately
  specified
• Must understand whole system to understand one
  class
• Solution
• Overcome program and aspects separation in
  visualization
• But keep obliviousness in the code
• To ensure code/visualization consistency need
  for automatic tools

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AJDT

• AJDT shows
• Join points selected by pointcuts
• For AJDT,
• AOP is an event-based programming.
• AJDT shows the locations of events.
• No modular reasoning
• Broken encapsulation
• Developers must see the internal implementation
  of a class to understand the program behavior.

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Our solution AspectScope

• Overcomes the limitations of AJDT
• Preserves modular reasoning
• More abstract reasoning
• Helps better understand programs

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AspectScope

• An outline viewer of a class
• Eclipse plug-in for AspectJ
• It shows the outline of a class woven with an
  aspect
• Modules classes, methods and fields
• Generates javadoc comments for modules
• Document how and when aspects extend their
  behavior

outline
javadoc
??? AspectScope ??
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Modular reasoning

• AspectScope enables modular reasoning
• No show of source code (the implementation of
  methods)
• Encapsulation is preserved.
• Still shows enough information to help
  understanding
• In AspectScope, an aspect is an extension to a
  class.
• AspectScope shows an extension by an aspect as
  part of the specification of a module
  interface.

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Modular reasoning

• Concrete benefit
• Abstracts the differences between some kinds of
  pointcuts, to simplify visualization
• Concrete example unified representation of
  execution pointcuts and call pointcuts

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Execution pointcut visualized by AspectScope

• AspectScope indicates
• an advice extends the behavior of a callee method.

after() execution(void Point.setX(int))
Display.update()
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Call pointcut (also get set)

• AJDT indicates..
• An advice intercepts a call in a caller method.

after() call(void Point.setX(int))
Display.update()
Caller class
AJDT Editor
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Call pointcut (also get set)

• Unlike AJDT, AspectScope indicates...
• An advice extends the behavior of a callee
  method.

after() call(void Point.setX(int))
Display.update()
Callee class
AspectScope
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Aspects as conditional extensions

• In AspectScope, aspects are module extensions
• But can be conditional within and cflow
  pointcuts
• Extension only if a caller satisfies a condition

after() call(void Point.setX(int))
within(Line) Display.update()
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javadoc comments

• Automatically generated or gathered from from
  source code of methods and advices

From the implementation of setX()
From the pointcut definition
From the advice definition
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Explaining pointcuts

• Interprets all AspectJs pointcuts into
  developer English

void setX(int)
pointcut move() call(void
Shape.set(int)) call(void
Shape.moveBy(..))
Wild cards , , and .. are expanded to
concrete name.
after() move() within(Line)
Display.update()
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Concrete example 1 Observer aspect

• An advice is executed when a setter method is
  called.

The advice is not executed when setX() is called
within setP1() in Line.
pointcut change() call(void Shape.set(..)) af
ter() change() !cflowbelow(change())
Display.update()
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AspectScope vs. AJDT
AJDT Editor
AspectScope
AJDT shows join point shadow at a caller side.
AspectScope shows how setP1() is extended for
notifying an observer of updates.
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Concrete example 2 Logging aspect

• Print a log message just before a method in
  Canvas calls draw() in Graphics.

class Canvas Image image void
paint(Graphics g) g.draw(image)

aspect LoggingAspect before() call(
Graphics.draw(..))
within(Canvas) System.out.println(log)

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AspectScope vs. AJDT
AJDT Editor
AspectScope
AJDT shows a caller-side expression.
before() call(void Graphics.draw(Image))
within(Canvas)
System.out.println()
AspectScope shows the extension to a callee-side
method.
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Related Work

• Aspect-Aware Interface Kiczales et al. 05
• It shares basic ideas with AspectScope.
• Conceptual framework for modular reasoning.
• This paper does not mention call, get, and set
  pointcuts.
• No javadoc comments.
• Not a practical development tool, unlike
  AspectScope.
• Classbox/J Bergel et al. 05
• Similar to the interpretation of aspects by
  AspectScope.
• Enables an extension only effective to a
  particular module.

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Conclusion

• AspectScope A programming tool for AspectJ
• An outline viewer of a class
• It shows the outline of a class woven with an
  aspect
• Declared methods and fields
• javadoc comments for the methods and fields
• How and when the aspect extends their behavior
• It enables modular reasoning

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Intertype declaration

• AspectScope indicates appended methods and fields.

public aspect UpdateSignaling Point
Point.getLocation()