AspectOriented Programming with AspectJ

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aspectj toolsnew and noteworthy
Mik Kersten University of British Columbia
Adrian Colyer IBM Hursley
OOPSLA, October 26-27 2004, Vancouver
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good modularity

• socket creation in Tomcat
• colored lines show relevant lines of code
• fits nicely into one package (3 classes)

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pretty good modularity

• class loading in Tomcat
• colored lines show relevant lines of code
• mostly in one package (9 classes)

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not so good modularity

• logging in Tomcat
• scattered across the packages and classes
• error handling, security, business rules,

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the cost of tangled code

• redundant code
• same fragment of code in many places
• difficult to reason about
• non-explicit structure
• the big picture of the tangling isnt clear
• difficult to change
• have to find all the code involved
• and be sure to change it consistently

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the aop idea

• crosscutting is inherent in complex systems
• crosscutting concerns
• have a clear purpose
• have a natural structure
• so, lets capture the structure of crosscutting
  concerns explicitly...
• in a modular way
• with linguistic and tool support

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The role of tool support

• IDE tools make code easy to navigate
• Reference structure embedded In the code
• Declaration lookup
• Structured search
• But inheritance structure can be hard to extract
  by reading code alone
• Especially in large systems
• E.g. who overrides this method?

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Join points

• Key points in program execution
• method constructor execution
• method constructor call
• field get set
• exception handler execution
• static dynamic initialization
• Demo

Line
end1Point
end2Point
moveBy(int, int)
moveBy(int, int)
moveBy(int, int)
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1.2 tools demo

• Figures
• Core language
• Spacewar
• Build configs
• Monitorlib
• Aspect libraries bytecode weaving
• WSIF
• Visualizer
• AJDoc

demo
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AspectJ 1.2 tools suite

• IDE plugins
• AJDT for Eclipse (up to 3.0)
• JBuilder (up to X)
• NetBeans (up to 3.4.2)
• Emacs
• Other tools
• Command line incremental compiler
• Bytecode weaver
• AJDoc
• Ant task
• AspectJ Browser

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Making do without AOP support

• Youre already working with crosscutting
  structure
• J2EEs XML descriptors, generative programming
• Structured search and refactoring tools can help
• But its not explicit

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Exposing crosscutting structure

• AspectJ express crosscutting directly
• Direct semantics enable good tool support
• Crosscutting structure is explicit
• Editor, views, documentation,
• Demo auxiliary aspects, views

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AOP reduces system complexity

• Aspects are a new language mechanism, so there is
  a learning curve
• But with good tool support AOP programs are
  easier to understand than their OO counterparts

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Whats next?

• Java 5 support
• Refactoring
• Java refactorings will update aspects
• AspectJ refactorings
• Aspect-oriented refactorings will help with
  migration and evolution
• Structure views
• Everywhere you seeOO structure you see the
  correspondingAO structure

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Other AOP tools

• AspectJ language compilers
• ajc production, IDE integration
• abc research, optimization
• XML language compilers
• AspectWerkz
• JBoss AOP
• Spring
• Joint point models, pointcuts, and advice are the
  common to each of these

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AspectJ credits

• Versions 0.1-1.1 developed at PARC
• Eclipse.org Technology project
• AspectJ team
• Andy Clement, Adrian Colyer, Erik Hilsdale, Wes
  Isberg and Mik Kersten
• AJDT team
• Matt Chapman, Andy Clement, Adrian Colyer, Mik
  Kersten and Julie Waterhouse
• http//eclipse.org/aspectj
• http//eclipse.org/ajdt