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A Meta-Level Specification and Profile for AspectJ in UML

A Meta-Level Specification and Profile for AspectJ in UML. Joerg Evermann School of Information Management Victoria University of Wellington. Yet Another AspectJ Profile?. Previous work based on UML 1.x UML 2.x extensions very different Integrated meta-level extensions

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A Meta-Level Specification and Profile for AspectJ in UML

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  1. A Meta-Level Specification and Profile for AspectJ in UML Joerg Evermann School of Information Management Victoria University of Wellington

  2. Yet Another AspectJ Profile? • Previous work based on UML 1.x • UML 2.x extensions very different • Integrated meta-level extensions • Meta-models are profiles • Full coverage of AspectJ • Full code generation capabilities • No textual specification or special code words • Rigorous meta-level based modeling • Supported by all MOF compliant tools

  3. Meta-Level Specification • CrossCuttingConcern • Not in AspectJ • But important for modularization • Extend Package meta-class • Related to Aspect through the meta-model level • Aspect • Static features • Pointcuts • Dynamic features • Advice • Generalizable • Similar to meta-model element Class Extension Relationships

  4. Aspects • isPrivileged • declareParents • Specifies meta-level Generalizations • declareImplements • Specifies meta-level InterfaceRealizations • Precedence • Total ordering • Instantiation • PointCut

  5. Advice • Advices are dynamic • BehavioralFeature • Expressible as state charts, collaborations, or opaque behaviour, i.e. methods • Related to Aspect via meta-model • Signatures by virtue of Operation • Subclass of BehaviouralFeature • Requires behavior specification by method • Determines when advice is applied (after throwing or after returning value)

  6. Static Crosscutting Features • Owned by / modelled with the aspect • For better separation of concerns and encapsulation • Requires specification of type for introduced features • Alternative possible • “Cleaner” meta-model • But less rigorous separation

  7. PointCuts • Explicit composition • UML has no built-in regular expressions • Refer explicitly to specific model elements they cut

  8. OCL Constraints • Advice stereotype only on behavioral features of classes that are stereotyped Aspect context Advice inv: allInstances.featuredClassifier.oclIsKindOf(Aspect) • StaticCrossCuttingFeature stereotype only for features of classes that are stereotyped Aspect context StaticCrossCuttingFeature inv: allInstances.featuredClassifier.oclIsKindOf(Aspect) • PointCut stereotype only for behavioural features of classes that are stereotyped Aspect context PointCut inv: allInstances.featuredClassifier.oclIsKindOf(Aspect)

  9. OCL Constraints (2) • Aspects are either instantiated perPointCut or perType context Aspect inv: perType->size() > 0 or perPointCut->size() > 0 • Aspect stereotype only on classes packaged in packages that are stereotyped as CrossCuttingConcern context Aspect inv: package.oclIsKindOf(CrossCuttingConcern)

  10. Code Generation • AspectJ from XMI • XSLT • approx 600 lines of code, 9 templates • Proof of concept • Lacking sufficient error handling • No support for templated and stereotyped classes (i.e. Java Generics and Annotiations) yet. • Modeller must ensure advice signature matches context exposed in PointCuts • Not all boolean combinations allowed in AspectJ

  11. Code Generation (2) • Advice signature (return parameter or raised exception) determines after … returning or after … throwing advice context Advice inv: if (adviceExecution = AfterAdvice) then ownedParameter(p | p.direction=return)->size() > 0 or raisedException->size() > 0 • Different interpretation of return parameter in advice signature • Ignored for before-Advice • Type of returned value for around-Advice • PointCut context for after-Advice

  12. Discussion • Rigorous Meta-model specification • Lightweight extensions • Cross-tool support (in theory) • Lack of pattern based textual specification • Requires awareness of base model • Safer • Easier model verification • No tool support required

  13. Where to from here? • Two main directions • Breadth: Other AOP languages • Depth: Generic Aspect Profile • Model Transformations for MDA • Other improvements • Code generation for templated and stereotyped elements (i.e. Java 5 generics and annotations) • Validity constraints with OCL • Usability and practical application studies

  14. Thank You

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