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Feb 17, 2024 280 likes •722 views

A Language Workbench for Creating Production-Ready Extensions to AspectJ Arik Hadas Dept. of Mathematics and Computer Science The Open University of Israel Advisor: David H. Lorenz Motivation Explicit join points looks interesting, let's

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A Language Workbench for Creating Production-Ready Extensions to AspectJ

Arik Hadas

  • Dept. of Mathematics and Computer Science

The Open University of Israel

Advisor:

David H. Lorenz

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Motivation

“Explicit join points looks interesting, let's evaluate it” abc? AWESOME? Spoofax? xtext?

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Our Research Goal

  • Tool for the development, evaluation and

production of extensions for AspectJ

– Like abc

  • Workbench, not a compiler

– Provide common editing tools – Compatible with AOP development tools

  • Generate production-ready extensions

– Work with a commonly used version of AspectJ – Proper support for programming in multiple

extensions simultaneously

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Limitations of the AspectBench Compiler (abc)

  • Used to be the default choice for

implementing AspectJ extensions

  • Not suitable for development of new

extensions

– Does not work with recent versions of AspectJ

  • Not suitable for evaluation of new

extensions

– Does not provide development tools – No support for advanced weaving semantics

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Language Workbench (LW) for Java

Language Workbench Language Workbench javac javac

DSL Code Java Bytecode

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Language Workbench (LW) for Java

Language Workbench Language Workbench javac javac

DSL Code Java Bytecode

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Will It Work for AspectJ?

Language Workbench Language Workbench javac javac

Java Bytecode

No Aspects

DSL Code Extension Code

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Will It Work for AspectJ?

Language Workbench Language Workbench javac javac

Java Bytecode

No Aspects

DSL Code Extension Code

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Replacing javac with ajc

Language Workbench Language Workbench

Extension Code Java AspectJ Bytecode Woven Bytecode javac ajc

No Multiple DSALs

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AOP Composition Framework (CF)

  • To work with multiple AspectJ extensions

simultaneously, one will need to define:

– Weaving semantics for co-advising – Weaving semantics for foreign advising

  • CF Allows to define the required semantics

– As opposed to ajc

  • CF does not provide editing tools
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LW vs CF

Language Workbench AOP Composition Framework

Tools for creation & usage of languages

 

Defining weaving semantics needed for DSALs

 

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Can We Enjoy Both Worlds?

Language Workbench AOP Composition Framework

?

Tools for creation & usage of languages

  

Defining weaving semantics needed for DSALs

  

Will a naive combination of the two be a proper solution?

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Naive Combination of LW and CF

Language Workbench Language Workbench

DSAL Code AspectJ Woven Bytecode ajc Composition Framework

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But We Still Lack AOP Tools..

Language Workbench Language Workbench

DSAL Code AspectJ Woven Bytecode Composition Framework

Browsing Debugging Compiling

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Traditional LW Architecture

Language Workbench Language Workbench

DSAL Code AspectJ Woven Bytecode

Composition Framework Code Transformation

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Our Workbench Architecture

Composition Framework Composition Framework

DSAL Code Woven Bytecode

Code Transformation Language Workbench Language Workbench

AspectJ DSAL Code

Compliance with AOP tools

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Our Workbench Architecture

Composition Framework Composition Framework

DSAL Code Woven Bytecode

Code Transformation Language Workbench Language Workbench

DSAL Code

Standalone DSAL compiler Can generate debugging & browsing information

Compliance with AOP tools

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Validation

  • We implemented a workbench
  • We Implemented third-party extensions that

were proposed to AspectJ

– COOL – Closure Join Points (CJP) – Explicit Join Points (EJP)

  • Available as an open source

– https://github.com/OpenUniversity

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Our Workbench Implementation

AWESOME* AWESOME*

DSAL Code Woven Bytecode

Spoofax Spoofax

DSAL Code

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AWESOME

ajc ajc

aspectjweaver aspectjweaver aspectjtools aspectjtools

AWESOME AWESOME

Pluggable weaver Pluggable weaver aspectjtools aspectjtools

AspectJ Code AspectJ Code

Code Transformation

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Enhancing AWESOME

ajc ajc

aspectjweaver aspectjweaver aspectjtools aspectjtools

AspectJ Code

AWESOME* AWESOME*

Pluggable weaver Pluggable weaver

Extension Code

Pluggable tools Pluggable tools

Code Transformation

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AWESOME's Weaving Model

List<BcelShadow> around(MultiMechanism mm, LazyClassGen clazz): reifyClass(mm,clazz) { ... } public List<IEffect> match(BcelShadow shadow) { ... } public List<IEffect> order(BcelShadow shadow, List<IEffect> effects) { ... } void around(MultiMechanism mm, List effects, BcelShadow shadow): execution(void MultiMechanism.mix(List, BcelShadow)) { ... }

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Extended Weaving Model

public void preweave(List<ResolvedType> types) { ... }

List<BcelShadow> around(MultiMechanism mm, LazyClassGen clazz): reifyClass(mm,clazz) { ... } public List<IEffect> match(BcelShadow shadow) { ... } public List<IEffect> order(BcelShadow shadow, List<IEffect> effects) { ... } void around(MultiMechanism mm, List effects, BcelShadow shadow): execution(void MultiMechanism.mix(List, BcelShadow)) { ... }

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So I've been asked to implement EJP...

CJP COOL EJP

AWESOME*

Weaving Compilatjon Code Transformatjon

Spoofax

Editjng Tools

DSAL code

Woven Bytecode

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CJP – Grammar Definition

sorts JoinpointDeclaration context-free syntax "exhibit" MethodName "(" {FormalParam ","}* ")" Block "(" {Expr ","}* ")" -> Expr{cons("ClosureJoinpoints")} "exhibit" MethodName Block -> Expr {cons("ShortClosureJoinpoints")} JoinpointDeclaration -> AspectBodyDec "joinpoint" ResultType Id "(" {FormalParam ","}* ")" Throws? ";" -> JoinpointDeclaration{cons("JoinpointDeclaration")} (Anno | MethodMod)* CJPAdviceSpec Throws? Block -> AdviceDec {cons("CJPAdvice")} "before" Id "(" {FormalParam ","}* ")" -> CJPAdviceSpec {cons("CJPBefore")} "after" Id "(" {FormalParam ","}* ")" -> CJPAdviceSpec {cons("CJPAfter")} "after" Id "(" {FormalParam ","}* ")" "returning" CJPSingleParam?

  • >CJPAdviceSpec {cons("CJPAfterReturning")}

"after" Id "(" {FormalParam ","}* ")" "throwing" CJPSingleParam?

  • > CJPAdviceSpec {cons("CJPAfterThrowing")}

"(" FormalParam? ")" -> CJPSingleParam {cons("CJPSingleParam")} ResultType "around" Id "(" {FormalParam ","}* ")"

  • > CJPAdviceSpec {cons("CJPAround")}

lexical syntax "exhibit" -> Keyword "joinpoint" -> PseudoKeyword

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CJP – Grammar Definition

"exhibit" MethodName "(" {FormalParam ","}* ")" Block "(" {Expr ","}* ")"

  • > Expr{cons("ClosureJoinpoints")}

"exhibit" MethodName Block -> Expr {cons("ShortClosureJoinpoints")}

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Programming in CJP with Eclipse

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But It Will Not Compile..

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CJP – Code Transformation

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CJP – Replacing ajc with AWESOME*

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CJP – Behind the Scenes

Original Code Transformed Code

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CJP Implementation

  • Passed all tests from original prototype

– Few invalid tests were fixed

  • CJP programs runnable in Eclipse

– Looks like regular AspectJ project

  • Non trivial extension

– Used context-aware code transformations

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Context-aware Code Transformation

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Context-aware Code Transformation

Need to know about the joinpoint declaration when transforming the base code!

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Another example: COOL

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AJDT Markers for COOL

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Another example: EJP

  • Implemented features that were omitted in
  • riginal prototype

– Pointcut arguments – Policy enforcement

  • Used the 'preweave' extension in the

AWESOME's weaving model

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Using the preweave phase

Empty pointcut Extending pointcut in base code

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Related Work

  • Language Workbenches

– [Fowler, 2005] Language workbenches: The killer-app for

domain specific languages.

– [Kats and Visser, 2010] The Spoofax language workbench:

Rules for declarative specification of languages and IDEs.

  • The AspectBench Compiler

– [P.A, A.S.C, L.H, S.K, J.L, O.L, O.M, D.S, G.S, and J.T, 2005]

abc: an extensible AspectJ compiler.

  • AOP Composition Frameworks

– [Lorenz and Kojarski, 2007] Understanding aspect interaction,

co-advising and foreign advising.

– [Kojarski and Lorenz, 2007] Awesome: An aspect co-weaving

system for composing multiple aspect-oriented extensions.

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Tools Comparison

abc AWESOME Spoofax Workbench

Tools for custom syntax definition Extensible Java/AspectJ syntax Tools for code transformation Editing tools for end-programmers Ability to define the weaving semantics required for DSAL Works with a recent version of AspectJ Compliance with AJDT

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Conclusion

  • A novel design for a workbench that produces

first-class AspectJ extensions

– A modern alternative to abc – AOP composition framework used as a back-

end to achieve first-class DSL

– DSAL code passed to the back-end to achieve

first-class AOP language

  • Validation

– Prototype comprising Spoofax and AWESOME* – Plug-ins for COOL, EJP and CJP

  • Future Work

– Evaluate AspectJ extensions in real-world cases

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Arik Hadas

  • Dept. of Mathematics and Computer Science

The Open University of Israel

arik.hadas@openu.ac.il

https://github.com/OpenUniversity

Thank You!