AspectMaps: Extending Moose to visualize AOP software

17 Pages·2013·0.72 MB·English

by  Johan Fabry

ScienceofComputerProgramming79(2014)6–22
ContentslistsavailableatScienceDirect
Science of Computer Programming
journalhomepage:www.elsevier.com/locate/scico
AspectMaps: Extending Moose to visualize AOP software
JohanFabrya,∗,AndyKellensb,SimonDenierc,StéphaneDucassec
aPLEIADLaboratory,ComputerScienceDepartment(DCC),UniversityofChile,Chile1
bSoftwareLanguagesLab,VrijeUniversiteitBrussel,Belgium2
cRMoDTeam,INRIALille-NordEurope,France3
a r t i c l e i n f o a b s t r a c t
Articlehistory: When using aspect-oriented programming the application implicitly invokes the
Received24January2011 functionality contained in the aspects. Consequently program comprehension of such
Receivedinrevisedform13November a software is more intricate. To alleviate this difficulty we developed the AspectMaps
2011
visualization and tool. AspectMaps extends the Moose program comprehension and
Accepted23February2012
reverseengineeringplatformwithsupportforaspects,andisimplementedusingfacilities
Availableonline10March2012
providedbyMoose.InthispaperwepresenttheAspectMapstool,andshowhowitcan
beused byperforminganexploration ofafairlylarge aspect-orientedapplication. We
Keywords:
thenshowhowweextendedtheFAMIXmeta-modelfamilythatunderpinsMoosetoalso
Aspect-orientedprogramming
Visualization providesupportforaspects.ThisextensioniscalledASPIX,andthankstothisenhancement
Moose Moosecannowalsotreataspect-orientedsoftware.Finally,wereportonourexperiences
usingsomeofthetoolsinMoose;Mondriantoimplementthevisualization,andGlamourto
buildtheuserinterface.Wediscusshowwewereabletoimplementasizablevisualization
toolusingthemandhowwewereabletodealwithsomeoftheirlimitations.
Note:Thispaperusescolorsextensively.Pleaseuseacolorversiontobetterunderstandthe
ideaspresentedhere.
©2012ElsevierB.V.Allrightsreserved.
1. Introduction
Aspect-oriented programming [18] is a novel programming paradigm that aims at modularizing what are called
crosscuttingconcerns.Duetothe‘‘tyrannyofthedominantdecomposition’’[27],particularconcerns,e.g.,logging,tracing,
transaction management, and so on, cannot be captured in individual modules using classical software engineering
techniques.Insteadtheirimplementationisscatteredthroughoutvariousmodules,hencecrosscuttingtheimplementation
oftheentiresystem.
Totacklethisproblem,aspect-orientationintroducestheconceptofanaspect:anovelkindofmodulethatcapturessuch
crosscuttingconcerns.Keytothenotionofaspectsisthefactthattheyintroduceanimplicitinvocationmechanism.Rather
thaninvokingthecrosscuttingbehaviorexplicitlyfromwithinthecodeofasystem,thisbasecodenolongercontainsthese
calls.Toallowimplicitinvocation,conceptually,eachexecutionstepoftheapplicationisreifiedasajoinpoint,e.g.,amethod
call,anassignment,... Anaspectthendefinesthebehaviortobeexecuted,anadvice,tooccuroncertainjoinpoints.These
areidentifiedbydefiningapointcut:apredicateoverjoinpoints.Inotherwords,whileanadvice4implementstheactual
∗
Correspondingauthor.
E-mailaddress:[email protected](J.Fabry).
1 http://pleiad.cl.
2 http://soft.vub.ac.be.
3 http://rmod.lille.inria.fr.
4 IntheAOSDliteraturetheterm‘advice’isusedinsteadof‘apieceofadvice’andthepluralof‘advice’remains‘advice’.
0167-6423/$–seefrontmatter©2012ElsevierB.V.Allrightsreserved.
doi:10.1016/j.scico.2012.02.007
J.Fabryetal./ScienceofComputerProgramming79(2014)6–22 7
crosscuttingbehavior,pointcutsselectatwhichpointsintheexecutionofthesystemtheadviceshouldbeexecuted.Finally,
thestaticlocationinthesourcecodethatgivesrisetoajoinpointatexecutiontimeiscalledajoinpointshadow.Insummary,
thefollowingprocess(conceptually)takesplaceforeachexecutionstepofthesoftware.Whenanexpressioninthesource
code,i.e.,ajoinpointshadow,isexecuted,itcausesajoinpointtobeemitted.Allpointcutsofthesystemareautomatically
calledwiththisjoinpointasargument,andforthepointcutsthatreturntruetheadviceassociatedtothispointcutisrun.
Althoughaspectsopenupnewpossibilitiesintermsofmodularizationofcrosscuttingconcerns,thepresenceofthis
implicit invocation mechanism can make it more difficult for a developer to understand the behavior of the system. In
literature, various problems have been documented that are caused by this implicit invocation mechanism. One such
problem is the fragile pointcut problem [17,19]. Due to the limited expressiveness of pointcut languages, such pointcut
expressionsareoftentightlycoupledtothestructureofthebasecode.Asaconsequence,seeminglysafechangestothis
basecodecanhaveanunexpectedanderroneousimpactonthebehavioroftheaspectsthataredefinedinthesystem.
Similarproblemscanoccurwhenmultipleaspectsinterveneatasinglejoinpoint.Asitisnotimmediatelyclearwhich
aspectsinterveneatasinglepointintheexecution,andastheseaspectspotentiallyinteractwitheachother,thiscanlead
toerraticbehavior[26].
To alleviate these problems and aid developers to understand such software we have proposed the AspectMaps
visualization [14]. AspectMaps aims to ease code comprehension of software using aspects by offering a scalable
visualizationofimplicitinvocation.TheAspectMapsvisualizationisalsoimplementedasatool,ontopoftheMoose[9]
reverseengineeringplatform,leveragingthefacilitiesofferedbythisplatform.
Thispaperbuildsuponourpreviouswork[14],andfeaturestwonovelcontributions:Ontheonehanditpresentsa
detailed discussion of the AspectMaps visualization tool, showing how it can be used to explore aspect-oriented code
of a fairly large application, yielding some interesting observations. On the other hand it provides a discussion of the
implementationofthetool.InthispartwefirstintroduceourextensiontoMoosethatallowsittoalsooperateonaspect-
orientedcode.ThisextensioniscalledASPIX;itaugmentstheFAMIX[28]meta-modelthatunderliestheMooseplatform
suchthatitsinstancescanmodelaspect-orientedsoftware.Second,wediscussourexperiencesofusingthetoolsoffered
byMooseforbuildingvisualizations:Mondrian[24],andfor(specifickindsof)userinterfaces:Glamour[5].Wereporthow
wewereabletousethesetoolstobuildareasonablylargevisualizationtool,whileavoidingsomeoftheirdrawbacks.For
anin-depthdiscussionregardingtheconceptsunderlyingourvisualization,theprosandconsofthevisualizationandan
initialempiricalvalidationofourapproachwerefertheinterestedreaderto[14].
Theintendedaudienceofthispaperistwofold,echoingthetwomaincontributionsofthetool.Ontheonehandwehave
thedevelopersofaspect-orientedsoftwarethatwanttouseAspectMapstogainabetterunderstandingofthesoftwareon
whichtheyareworking.OntheotherhandwehavedevelopersusingMoosethatmaywanttobuildtheirownanalysistool
foraspect-orientedsoftware,orthatmaygainfromourlessonslearnedbuildingalargeanalysistoolusingthefeaturesof
Moose.
Thispaperisstructuredasfollows:WestartwithgivinganintroductiontotheAspectMapsvisualization,andinSection3
we present the tool, followed by an example case study showing how it can be used. Section 4 introduces ASPIX, our
extensiontotheFAMIXmeta-modelthatallowsMoosetobeusedtoanalyzeaspect-orientedsoftware.Thisisfollowed
inSection5byareportofourexperiencesonusingMoosetobuildtheAspectMapstool.Section6givesanoverviewof
relatedwork,andSection7discussesfutureworkandconcludes.
2. TheAspectMapsvisualization
AspectMapsisavisualizationthatoffersusersadetailedoverviewofimplicitinvocation.Itvisualizeswhereaspectsare
specifiedtoapplyinasystem,basedonvisualizingjoinpointshadows,andhowaspectspossiblyinteractateachjoinpoint
shadow.Moreoverthisisperformedinascalableway,thankstoamultilevelselectivestructuralzoom.Notethatthispaper
doesnotfocusonthevisualizationitself:adiscussionofthedesignrationaleofourvisualization,itsmeritsandlimitation,
andasmalluserstudycanbefoundin[14].WethereforehereonlygiveasummaryoftheAspectMapsvisualization,adapted
from[14],beforediscussingthetool.
Forthesakeofthisdiscussion,wedefinethatanaspectappliesatacertainsourcecodeelement(apackage,class,or
method)ifforatleastonepointcutthatisassociatedwithanadviceofthataspect,atleastoneofitsjoinpointshadows
belongtothatelement.
AspectMapssupportsthetraditionalpointcut–advicemodelofaspectsappliedtoobject-orientedclass-basedlanguages.
Thejoinpointswevisualizearemethodcallsandmethodexecutions.Advicecanexecutebefore,aroundorafterajoin
point,andwedistinguishbetweenafterreturningandafterexceptionthrowing.Aspectsmaycontainvariousadvice,and
anexecutionordermaybespecifiedbetweenaspects.TheaboveeffectivelyallowsustovisualizeasubsetofAspectJ[18]and
Javacode(whichisarguablythemostpopularaspectlanguagecombination).Inthiscaseweignoreinter-typedeclarations
aswellasadvicethatappliestofields.TheAspectMapstoolishowevernotfundamentallyrestrictedtotheAspectJ/Java
combinationandmoredetailonthisisgiveninSection4.
The key feature of AspectMaps is having the ability to selectively zoom in on the source code at different levels of
granularity.Zoominginfromacoarserleveltoamorefine-grainedlevelrevealsmoredetail.Thebehaviorisanalogous
tostreetmapapplications,e.g.,GoogleMaps,hencethenameAspectMaps.
8 J.Fabryetal./ScienceofComputerProgramming79(2014)6–22
Fig.1.Compactvisualizationofpackages:coordinationandspacewar.
SpaceObject Pilot
Player Robot Display
Fig.2.Extendedvisualizationofthespacewarpackage(annotatedwithselectedclassnames).
To detail the AspectMaps visualization, the remainder of this section is structured following its different levels of
granularity.Foreachlevelweshowhowitisvisualized,andillustratethetoolusinganumberofexamples.Specifically,for
Sections2.1and2.2weuseSpacewar,anexampleprogramthatisprovidedwiththeAspectJDevelopmentToolkit(AJDT)[7]
andisalsoincludedasexampleintheAspectMapstool.Spacewardefinesmultipleaspects.Forthisdiscussionwevisualize
theCoordinationaspectingreenandtheEnsureShipIsAliveaspectinred.InSection2.3,weuseanadditionalartificially
createdexample,asSpacewardoesnotsufficetoshowallthefeaturesofAspectMaps.
AdditionalmaterialisavailableattheAspectMapswebsitehttp://pleiad.cl/aspectmapse.g.,featuringsomescreencasts
ofthetoolinaction.
2.1. Packagelevel
When opening the tool, AspectMaps provides an overview of all packages in the visualized system. Each package is
representedbyacompactvisualizationthatshowsthenameofthepackageandtheaspectsthatapplytothispackage.The
coloroftherectangleofeachpackagecorrespondstothecoloroftheaspectthatapplies,ifthataspectiscurrentlyenabled
forvisualization.Inthecasethatmultipleaspectsapplytoasinglepackage,thisisindicatedbythecolorblack(whichnever
canserveasthecolorofanaspect).ThispackagevisualizationisshowninFig.1.Thisfigureshowstwopackages,namely
coordinationandspacewar.Asmultipleaspectsinterveneinthespacewarpackage,itisindicatedinblack.Packagecontents
isnotshownatthismoment.
AuserofAspectMapscanobtainanextendedvisualization,revealingthepackagecontents,byzoominginonaselected
package(clickinginapackage).Fig.2showsthisextendedvisualizationappliedtothespacewarpackage.Insideofthe
package,alldifferentclassesandaspectsbelongingtothatpackageareshown.Thissameextendedvisualizationisshownin
apop-upwhentheuserofthetoolhoversthemousepointeroverapackagethatisrepresentedinthecompactvisualization.
OurextendedpackagevisualizationisinspiredbytheworkofLanzaetal.onPolymetricViews[21].Wehaveextended
thisworktoalsosupportthevisualizationofaspects.KeytoPolymetricViewsisthatthedimensionsoftheentitiesreflect
particularpropertiesoftheseentities(e.g.,LOC,numberofmethods).Atthislevelofdetail,ourvisualizationshowsthe
followinginformation:
• Classes:rectangleswithblackborders.InheritancerelationsarevisualizedusingUMLnotation.
• Aspects:rectangleswiththickcoloredborders.Thebordercoloristhecolorfortheaspect(neverblack).
• Whereaspectsapply:classrectangleshavethecoloroftheaspectthatapplies,blackformultipleaspects.
• Classandaspectmetrics:theuserselectswhichdimensionreflectswhichmetric,ornone.Forthefiguresinthissection
weselectnometric,forclarityofthediscussion.
SimilartotheoriginalPolymetricViewsvisualization,AspectMapsdoesnotdisplaythenamesoftheclasses,inorder
topreventclutteringthevisualization.Thesenamesareinsteadrevealedattheclasslevel,whereclassesandaspectsshow
theirextendedvisualization.Thisvisualizationisshownasapop-upwhenthemousehoversoveraclassoraspect,orwhen
theuserperformsazoomoperationonaclassoraspectbyclickingonit.
2.2. Classlevel
Classesarerepresentedinourvisualizationusingrectangles.Atthetopoftherectangle,andseparatedfromtherestofthe
rectanglebymeansofahorizontalline,thenameoftheclassisshown.Belowthehorizontallinewerepresenttheinstance
J.Fabryetal./ScienceofComputerProgramming79(2014)6–22 9
run
keyPressed
keyReleased
Fig.3.TheDebugaspectandthePilothierarchy(annotatedwithselectedmethodnames).
Method Name
Before
Execution
Around
Call Shadows
Execution
After
Execution
Fig.4.Templateforvisualizationofexecutionshadowpoints(left),andanexampledestroymethod(right).Fig.7showscallvisualization.
variables(asdiamonds)andmethods(smallerrectangles)oftheclass.Theheightandwidthofmethodscanbedetermined
byametric.Themethodsarecoloredbasedontheapplicableaspects,takingintoaccountthatmultipleaspectsintervening
atasingleentityarecoloredblack.Bymeansofapop-upontheclassname,theusercangetadditionalinformationofthe
class(itssuperclass,thenamesandtypesoftheinstancevariables).
Aspectsarevisualizedinasimilarfashion,wherethenameoftheaspectisindicatedabovethehorizontalline.Belowthe
linewecanfindtheadvice(shownasrectangles)andpointcuts(shownasovals).Thedimensionsoftheadvicecanalsobe
customizedbyauser-selectedmetric.Pop-upsfortheaspectshowthesuperaspect;forpointcutstheyshowthenameofthe
pointcut.Pop-upsforadviceshowtheirsignatureandlinenumberintheaspect,asanadvicesignaturedoesnotuniquely
identifyanadvice.
Fig.3showsourvisualizationzoomedinonalltheclassesinthehierarchyofPilot,andalsoshowstheDebugaspect.The
visualizationshowsthattherearemultipleaspectsapplyingtomethodrundefinedontheclassGame.Furthermore,wesee
thattheaspectEnsureShipIsAliveappliestomethodskeyPressedandkeyReleased.
2.3. Methodlevel
ThemethodlevelisthefinestlevelofdetailofferedbyAspectMaps.Atthislevel,ourvisualizationshowshowaspects
interveneattheshadowpointswithinthemethod.Notethatmultipleaspectscaninterveneatasinglejoinpoint,andthat
advicecanbedeclaredtoexecutebefore,afteroraroundthejoinpoint.Tocorrectlyreflectthesemanticsofsuchajoinpoint
model,ourvisualizationofshadowpointsmustrepresentthisinformationaccordingly.
Fig.4(left)showsthevariousregionsofourvisualizationofmethods.Fromtoptobottom,ourvisualizationshowsthe
nameofthemethodfollowedbyseparateboxescontainingbefore,afterandaroundadviceappliedtoexecutionshadow
points.Adviceapplicabletocallshadowpointsisdisplayedwithinaseparatebox(alsoseeSection2.3.2).Ontherightofthe
figure,ourvisualizationisillustratedonamethodnameddestroy.Wecanseethattheblueaspectappliesbeforeandafter
theexecutionofthismethod.
Bymeansofapop-uponthemethodname,usersofthetoolcanaccesstheparameterlistofthemethod.
2.3.1. Adviceexecution,Run-timetests,Ordering
Foreachapplicableadvice,ourvisualizationdrawsasmallfigurerepresentingtheshadowpointinthecorresponding
divisionofourmethod-levelvisualization.Thecolorofthisrectanglecorrespondstothecoloroftheaspect.Withinasingle
10 J.Fabryetal./ScienceofComputerProgramming79(2014)6–22
after throwing
4 after
advice
advice
order of advice with
execution runtime test
Fig.5.Fourafterexecutionadviceofasetmethod.
2 before
advice execution
order
2 around
due to
advice
precedence
declarations
4 after
advice
Fig.6.Eightexecutionadviceforagetmethod,withtwoprecedencedeclarationsyieldingthreeorderingarrows.
Method Name
Shadow 1
Call Shadows Shadow 2
Shadow 3
Before Around After
Fig.7.Templateforcallshadowpoints.
divisionofourvisualization,theserectanglesarestackedvertically.Asanillustrationofthis,considerFig.5thatshowsthe
afterexecutionadviceofanexamplesetmethod.
AspectMapsmakesthedistinctionbetweenafterthrowingadvice(shownusingtriangles)andallotherkindsofadvice
(representedbyrectangles),inordertoemphasizethespecialnatureofafterthrowingadvice:itexecuteswhenthemethod
terminatesbythrowinganexception.Ifthereisarun-timetestinvolvedinevaluatingthepointcutforanadviceexecution
(e.g.,anif-testoracontrol-flowpointcut)thefigurehasathickborderinacontrastingcolor(forexample,thegreenaspect
inFig.5).
Notethatitispossibleformultipleadviceofthesameaspecttoapplyatasingleshadowpoint.Thisisrepresentedin
AspectMapsbyvisualizingafigureforeachapplicationoftheadvice.Theorderinwhichtheseadvicewillbeexecutedis
indicatedbymeansofagrayarrow.Forexample,inFig.5theregularafteradviceoftheredaspectoccursbeforetheafter
throwingadvice.Whenmultipleadviceofdifferentaspectsapply,theorderoftheirapplicationmaybespecifiedbythe
programmer.Ifsuchanorderisspecified,AspectMapsindicatesthisorderbymeansofablackarrow.Anexampleofthis
isshowninFig.6.Consideringtheafteradvice,thecyanandredcodeisrunbeforethepinkadvice.Thereisnoordering
specifiedbetweenthegreenaspectandanyoftheotheraspects,norbetweenthecyanandredaspects,hencenoarrowsare
drawn.Fig.5doesnotshowanyblackarrows,indicatingnoorderingisspecifiedbetweenthegreen,brownandredaspects
andthereforenoclaimscanbemadeabouttheorderatwhichtheaspectswillbeexecutedatrun-time.
2.3.2. Callshadowpoints
Thebodyofamethodmaycontainmultiplecallshadowpoints,sequentiallyorderedbythesourcecodeofthemethod.
Wevisualizeadviceexecutioninthissameorder,aligningthemvertically.Thevisualizationofcallshadowpointsusesthe
samevisualizationasexecutionshadowpoints.Ithoweverordersthebefore,aroundandafterdivisionshorizontallyinstead
ofvertically.AtemplateofthisisshowninFig.7.
J.Fabryetal./ScienceofComputerProgramming79(2014)6–22 11
Fig.8.AselectionofmethodsinSpacewarshowingcallshadowpoints,aswellasapop-upofoneadviceexecution(inthenewPlayermethod).
Fig.9.TheAspectMapstoolshowingapartofSpacewar.Aboveisthevisualization,belowisprojectselection,visualizationofaspectselection,zoom
shortcutbuttonsandmetricsselection.Nonvisiblemetricschoices:classwidthisAttributes,aspectheightisLOC(linesofcode).
Anexampleofthevisualizationofcallshadows–appliedtoanumberofmethodsoftheSpacewarexample–canbe
foundinFig.8.Thisfigurealsodemonstratesthepop-upinformationforeachadviceexecutionthatcontainsthesignature
oftheadvice,thelinenumberoftheaspectinthesourcecodeandthesourcecodeoftheshadowpoint.
3. UsingAspectMaps
TheAspectMapsvisualizationhasbeenimplementedinPharo,aversionofSmalltalk,usingMoose[9],aplatformfor
softwareanalysisandreverseengineering.TheresultingtoolisalsocalledAspectMaps.Itisastandalonetoolthatinits
currentincarnationcanvisualizeAspectJ/JavacodedevelopedwiththeEclipseAspectJDevelopmentToolkit[7].
WeintroducethetoolhereandhowitislinkedtoEclipsebeforedescribingasoftwareexplorationsessionusingthetool.
TheimplementationoftheAspectMapstoolisdiscussedinSections4and5.
3.1. TheAspectMapstooluserinterface
TheAspectMapstoolconsistsofasinglewindow,showninFig.9.ThetoppartofthewindowshowstheAspectMaps
visualization,andthebottompanelcontainsmultiplecontrolsthatdeterminewhatisvisualizedandhow.Wepresentthese
controlsnext,followedbyadescriptionofthecontextmenuofthevisualization.
12 J.Fabryetal./ScienceofComputerProgramming79(2014)6–22
Available projects. AspectMaps allows for multiple Java projects to be visualized. In the figure these are AMTest and
Spacewar2.Selectingaprojectshowsthevisualizationinthetoppartofthewindow,andpopulatestheAspectsinProjectlist.
Thehierarchyofpackagesinaprojectisalsoavailableasaflattenedlist,byclickingontheexpansiontriangleshownbefore
theprojectname.InthefigurethisisshownforSpacewar2.Selectingapackagefromthislistrestrictsthevisualizationto
onlyshowthispackage.
AstheAspectMapstoolisnotintegratedinanexistingJava/AspectJdevelopmentenvironment,thecodethatisvisualized
needstobeimportedintothetool,whichaddsittothelist.ImportingisrequiredbecauseAspectMapsdoesnotoperateon
the original source code, but builds its internal model in order to visualize it. (This process is discussed in Sections 4.1
and4.2.)AprojectcanberemovedfromtheAspectMapstoolrepository,nolongermakingitavailableforvisualization,
byclickingonthetrashicon.Clickingonthefoldericonlaunchesanimportwizardthatwilladdtheprojecttothemodel
repository.Importingisatwo-stepprocess:firsttheaspectualinformationoftheprojectisobtainedbyaskingforan.xcr
fileoftheproject.SecondtheOOstructureoftheprojectisretrieved,eitherbyindicatingthesourcecodedirectoryofthe
projectorbyprovidinga.mseMooseexchangefilefortheproject.Howtogenerateboth.xcrand.msefileisdiscussedin
Section3.2.
Aspectsinproject. Twosettingsfortheaspectsintheprojectthatiscurrentlybeingtreatedarespecifiedhere.Firstly,each
aspectnameisshowninthecolorthatrepresentsitinthevisualization.Acontextmenuontheentriesinthislistallows
theircolortobechangedbyselectingitfromalistofcolors.Secondly,visualizationofjoinpointshadowsofeachaspect
canbeturnedonoroff.Forexample,inFig.9,visualizationofDebugisturnedon,whileforCoordinatoritisoff.Thecontext
menuontheentriesinthelistallowsthisvisualizationstatetobetoggled.Clickingthecheckiconturnsonvisualizationof
allaspectsinthelist,exceptfortheselectedaspect,ifany.Clickingthecrossiconperformstheinverse.
Structuralzoom. Thestructuralzoombuttonsperformsevendifferentzoomoperationsontheentitiesbeingvisualized.In
ordertheseare:
ByQuery: Givenaquery,whichmaycontainwildcards,zoomsinmaximallyonentitiesofwhichtheirnamesmatch.
EnabledAsp: Zoomsinmaximallyonalljoinpointshadowsofaspectsthatareturnedonforvisualization.
MultipleAsp: Zoomsinmaximallyonalljoinpointshadowswheremultipleaspectsthatareturnedonarepresent.
MaxIn: Maximalzoomlevelonallentitiesinthevisualization,i.e.,allentitiesshowtheirextendedrepresentation.
Classcontents: Levelshowingcontentsuptoclassesandaspects,allmethodsshowingtheircompactrepresentation.
Pkgcontents: Zoomlevelwherethepackagesshowtheircontents,andlowerlevelsshowthecompactrepresentation.
Maxout: Zoomlevelwhereallentitiesshowtheircompactrepresentation.
Classes, Methods, Aspects, Advice. These four tabs allow for a specification of the dimensions of the rectangles that
representtheseentities,whendrawninthecompactrepresentation.ThisistakenfromPolymetricViews[21],asdiscussed
in Section 2.1. By default the value here is constant, yielding small squares for each entity. Selecting a metric for a
dimension,e.g.,LOCfortheheightofclassesinFig.9,specifiesthatthesizeofthisdimensionisequaltothevalueofthis
metricfortheentitythattherectanglerepresents.Furtherconsideringtheclassesintheexample,thewidthofclassesisset
totheAttributesmetric,indicatingthenumberofattributes.Thetallclassrectangleshencearelargeclasses,andthewide
classeshavealargenumberofinstancevariables.Notethatmetricsonlyapplyonthecompactrepresentation,asinthe
expendedrepresentationthesizeofanentityrectanglemayneedtoexpandtoshowitscontents.
Context menu of the visualization. The last control of the visualization is the context menu that is available on selected
entitiesthatarebeingvisualized.Wehavethefollowingcontextmenuitems:
Onpointcuts: Revealingalljoinpointshadowsofthispointcutbyzoominginonthemethodscontainingthem.
Onadvices: Revealingalljoinpointshadowsofthepointcutofthisadvice.
Onadviceexecution: Revealingtheaspectoftheadviceandrevealingalltheexecutionsofthisadvice.
3.2. GeneratingimportfilesforAspectMaps
Assaidpreviously,tovisualizeaprojectitfirstneedstobeimportedintoAspectMaps.Thisimportprocesstakesonthe
onehandtheOOstructureoftheapplication,i.e.,whatisdefinedbytheJavacode,andontheotherhandtheaspectual
information,i.e.,whatisdefinedbytheAspectJcode.TheimportprocessitselfisdiscussedinmoredetailinSections4.1and
4.2,wedescribeherehowtoobtainthefilesrequiredtoperformanimport.
ToimporttheOOstructureoftheprojecttheAspectMapstoolrequiresa.msefilethatcontainstherelevantdataofthe
projectbeingimported.As.mseisthestandardfileformatforMoosedatainterchange,therearemultipletoolsavailable
thatproducea.msefilefromaJavasourcedirectory.OneoptionistheinFamixtoolbyintooitus,5asecondpossibilityto
5 http://www.intooitus.com/products/infamix.
J.Fabryetal./ScienceofComputerProgramming79(2014)6–22 13
Fig.10.Thecrosscutreportplugintoolbarbutton(theshamrock)openstheconfigurationdialog.
generatesuchfilesistouseVerveineJ.6AspectMapshassupportforbothtools(limitedtoUNIX/MacOSX):itcanusethem
togeneratethe.msefileontheflywhenimporting,thusstreamliningtheprocess.
AnotabledrawbackofusingJavasourcecodetogeneratethe.mseisthatthecodebeingexaminedmustbecorrectand
fullycomplianttotheJavastandard.ThisisrelevantastheAspectJcompiler,usedinEclipseAJDT,alsoaccepts.javafiles
whereaspects,pointcutsandadvicearedefined.ThereforesomeprojectsthatcompilesuccessfullywiththeAJDTcannot
beimportedintoAspectMaps.Tosolvethis,thedevelopermustensurethatallaspectualcodeisdefinedinAspectJ.ajfiles,
notin.javafiles.
TheaspectualinformationofaprojectisgeneratedbyanEclipseplug-inweimplemented.Theplugin,calledXCutreport,
istriggeredbyasuccessfulAspectJcompilation.AfteranAspectJprojectiscompiled,itproducestherelevantaspectual
information.Thepluginhasastraightforwardconfigurationdialogbox,showninFig.10.Outputcanbeturnedoff(the
defaultstate,whicheffectivelydisablestheplugin),shownontheEclipseconsoleorwrittentoan.xcrfile(orbothofthe
latter).The.xcrfileformatandtheXCutreportpluginarediscussedinmoredetailinSection4.2.1.
3.3. Examplecase:AJHotDraw
ToshowhowtheAspectMapstoolcanbeusedtoexploreagivenapplication,wenowpresentastudyofAJHotdraw[8]
usingAspectMaps.Wechosethisapplicationasitisawidelyknownexampleofanaspect-orientedapplication.AJHotdraw
isafairlylargeapplication,consistingof374classesand31aspects,whichservestoillustratethescalabilityofourtool.A
fullinvestigationoftheAJHotdrawcodeisoutsideofthescopeofthispaper.Werestrictourdiscussionheretoshowing
howthetoolwasusedtoreachsomenotableconclusionsfromourexploration.
• Afirstassessmentofthelocationofclassesandaspects,usingthePkgcontentsbuttonshowsthatalltheaspectsare
withintheccconcernspackagehierarchy.
• LookingatthenamesofaspectsintheAspectsinProjectlist,weseethatofthe31aspects,atleast15arededicatedto
undooperations.
• Selecting the ccconcerns.tools.undo package in the Available projects (restricting the visualization to only show that
package)showsthatitcontainsfiveundoaspects.PerformingaMaxinzoomoperationrevealsthatnoneofthesecontain
apointcutnoranadvice.(Sourcecodeinspectionrevealsthattheseaspectsonlyperforminter-typedeclarations,which
arenotvisualizedinAspectMaps.)
• Investigatingthecontentsoftheotherccconcernspackageinthesamewaywefindthattheother10undooperationsare
locatedinthepackageccconcerns.commands.undo.ThesehaveanamethatendsinUndo,exceptforUndoRedoActivity.
Alloftheformeronlyhaveonepointcut.Usingthecontextmenuitemthatrevealstheshadowsofthepointcutwelearn
thateachoftheseaspectssolelyaffectstheexecutemethodofaclasswiththecorrespondingname,withouttheUndo
suffix.AlloftheaffectedclassesaresubclassesofAbstractCommand.Thisisshownbytheinheritanceedgeforsubclasses
inthesamepackage,andalsobytheclassnamepop-upforsubclassesinadifferentpackagethanAbstractCommand.
• UsingtheNum ShadowsmetricweseethatoneofthetwomostimportantaspectsisCommandContracts.Enabling
visualizationofthisaspectonlyusingthetoolbariconandperformingaEnabledAspzoom,showsthatitaffectsthe
executemethodthatispresentinalmostallclassesoftheAbstractCommandhierarchy.Manualzoomingandexploration
oftheclassesinthehierarchythatarenotaffectedrevealthatthesedonotcontainanexecutemethod.Accordingtothe
samemetric,theotherimportantaspectisUndoableCommand.Investigatingthisaspectinananalogousfashion,we
seeitonlyaffectstheAbstractCommandclassand6moreclasses,eachofwhichisasubclassofaSwingcomponent:4
menu-relatedclasses,andthebuttonandcombo-boxclasses.
6 http://www.moosetechnology.org/tools/verveinej.
14 J.Fabryetal./ScienceofComputerProgramming79(2014)6–22
InadditiontoastudyofAJHotdraw,AspectMapshasbeenusedtoexploreSpacewar[14].Wealsohaveperformedauser
studythatrevealsthatonanexplorationofSpacewar,AspectMapsfaroutperformsthevisualizationofAJDT[14],which
isarguablythemostcompetitivesoftwarevisualizationforaspect-orientedsoftware.Again,adiscussionoftheseresultsis
outsideofthescopeofthispaper,asherewefocusonthetool,andwerefertothepublishedarticle[14]formoreinformation.
4. AddingaspectsupporttoMoose
TheAspectMapstoolisbuiltontopofMoose[9],aplatformforsoftwareanalysisandreverseengineering.Mooseoffers
variousfacilitiesforbuildingsoftwareengineeringtools,rangingfromimportingdata,source-codemodelingandquerying,
tobuildingsoftwarevisualizations.Inthepast,Moosehasbeensuccessfullyleveragedforbuildingawidevarietyoftools,
suchasTorch[29](atoolsupportingsource-codechangeintegration),SmallDude[4](aduplicationdetector),andeDSM[22]
(atooltodetectcyclicdependencies).Withinthecontextofthiswork,weoptedtobaseourtoolonMooseforthefollowing
reasons:
• FAMIX. FAMIX [28] is a language-independent meta-model for class-based programming languages that underpins
the Moose tool suite. Using this model allows AspectMaps to achieve a certain level of base and aspect language
independence.AdownsideisthatFAMIXhoweverdoesnotprovideconceptsforrepresentingaspect-orientedconstructs.
• Mondrian.Mondrian[24]isadomain-specificlanguageforscriptingvisualizationsthatispartoftheMoosetoolsuite.
Itisparticularlywell-suitedforimplementingAspectMapsasitdoesnotonlyofferconstructsfordeclaringthedifferent
nodesandedgesthatmakeupavisualization,butalsoprovidesameanstocreatehighly-interactivevisualizations.
• Glamour.SimilartoMondrian,Glamour[5]isadomain-specificlanguageforscriptingbrowsers.Itprovidesaconvenient
wayfordeclaringandcomposingtheuser-interfacecomponentsofAspectMaps.
• Integrationwithothertools.ByimplementingAspectMapsontopoftheMooseplatform,wecanalsoleveragetheother
toolsthatarepartoftheMooseplatform(tocalculatemetrics,...).
Assaidabove,Moosedoesnotprovidesupportforanalyzingaspect-orientedsoftwareastheFAMIXmeta-modelfamily
lackstherequiredconcepts.Toaddressthisshortcoming,weprovidedanextensiontoFAMIXthataddsthissupport,called
ASPIX.ASPIX(ASPectsInfamiX)isagenericclass-basedobject-orientedmeta-modeltowhichtheessentialaspect-oriented
conceptshavebeenadded.TheASPIXmodelisgenericsuchthatitcanbeusedbyalloftheMoosetools,i.e.,enablingMoose
tobeusedtoanalyzeaspect-orientedsoftware.Moreover,basingAspectMapsonASPIXallowsourtooltobeusedforother
combinationsofbaselanguagesandaspectlanguages.Thisaslongastheyfollowthe,arguablyprevailing,modelofaspects
beingcomposedofpointcutandadvice.
InthissectionweprovideadescriptionofASPIXanddetailhowmodelinstancescanbecreated,i.e.,howaspect-oriented
codeisrepresentedinourMooseextensionandhowthiscodecanbeimportedforanalysis.
4.1. ASPIX:ASPectsInfamiX
Toperformvisualization,AspectMapsdoesnotconsidertheactualsourcecodeoftheprogram,butinsteadusesitsown
model,asdotheothertoolsofMoose.ThismodelisaninstanceoftheASPIXmeta-model,amemberoftheFAMIXmeta-
modelfamily[9,12,28],whichwecreatedsuchthatMooseisabletoworkwithAOPcode.ASPIX(ASPectsInfamiX)consists
ofagenericclass-basedobject-orientedmeta-modelenrichedwithinformationofaspects,pointcuts,advice,adviceordering
andshadowpoints.AnalogouslytoFAMIX,theideaistohavelanguage-specificimportersthatgeneratemodelinstances.
Thesecanobtaintherequiredinformationfromthesourcecode.AspectMapscurrentlyonlyhasoneimporterforabase
andaspectlanguagecombination:JavaandAspectJ.InthissectionwefirstgiveanoverviewofFAMIX,beforewedetail
ouraspect-orientedextensionASPIX.Thenextsectiondetailshowinstancesofthemodelarebuiltbasedonthedatamade
availablebytheimporter.
ThecoreofFAMIXisalanguageindependentmeta-modelthatdescribesthestaticstructureofobject-orientedsoftware
systems.TheFAMIXcorecandescribethestructureofobject-orientedsystemsfromthenamespaceleveldowntovariable
accesses and method invocations. Fig. 11 shows relevant parts of FAMIX core (in gray) that are directly involved in
AspectMaps.Namespaceistheentitywiththehighestgranularity:itisusedtorepresentJavapackagesinthecaseofJava
systems.Typeisthemeta-descriptionforentitiescontainingmethodsinFAMIX(asindicatedbyitsmethodsattribute)and
ClassisaspecializationofType.BehaviouralEntityisagenericmeta-descriptionforbehaviors,suchasitsspecialization
Method.ItcancontainoutgoingInvocations(forexample,methodcalls)whichthemselvesaredescribedbyInvocation.
ASPIXextendstheFAMIXcorewithmeta-descriptionsspecifictothestructureofanaspect-orientedsystem.Fig.11
shows(inblack)themeta-descriptions,attributes,andinheritancerelationshipswhichconstituteASPIXasanextensionto
FAMIX.Hence,AspectisaspecializationofTypeandcontainsnamedPointcutsandadvices.AnAdvicehasakind(before,
after,oraround),aprecedenceOverrelationshiptoindicateprecedenceoftheadviceoverotheradvices,andarelationto
itspointcut(whichcanbeanamedpointcutoftheaspectoritsownanonymouspointcut).Pointcutholdsabooleanflag
indicatingwhetherevaluatingitrequiresaruntimetest.ItalsopointstojoinpointShadowscapturedbythispointcut.The
meta-descriptionJoinPointShadowholdstheoppositerelationinitsmatchingPointcutsattribute.Inthecurrentversionof
ASPIX,twokindsofjoinpointshadowsaredescribed:ExecutionJoinPointwhichlinkstoamethodandCallJoinPointwhich
J.Fabryetal./ScienceofComputerProgramming79(2014)6–22 15
Pointcut
Namespace Type
body: String
classes
methods hasRuntimeTest: Boolean
aspects
joinpointShadows
Class Aspect BehaviouralEntity
namedPointcuts outgoingInvocations
advices sourceRange: Interval
ExecutionJoinPoint Method Advice
kind: String
method joinpointShadow
JoinPointShadow pointcut
baseLineNumber: Integer precedenceOver
matchingPointcuts CallJoinPoint Invocation
baseCallString: String
joinpointShadow
expression
Fig.11.ClassdiagramoftheASPIXmeta-model,withrelevantpartsoftheFAMIXcoremeta-modelshowningray.
linkstoanexpression(aninstanceofInvocation).NotethatbothMethodandInvocationareextendedbyASPIXtolinkback
totheirrespectivejoinpointShadow,whileNamespaceprovidesalinktoitscontainedaspects.
4.2. ConstructinganASPIXmodel
ASPIXmodelsforJavaandAspectJcodearecreatedusingatwo-stepprocessasoutlinedinSection3.2.FirsttheJavaand
AspectJcodeareanalyzedandtherelevantdataisexportedtoanexchangeformat:an.msefileforJavaandan.xcrfilefor
AspectJ.SecondtheASPIXmodeliscreatedbasedonjoiningtheinformationinthesetwofiles.Therationaleforthistwo-
stepprocessusingexchangeformatsistwofold.Ontheonehandwemaintainaloosecouplingbetweenthedifferentparts
oftheloadingoperation.Ontheotherhand,intheimplementationweareabletoreuseasmuchexistinginfrastructureas
possible.
Theformerisimportantasitallowsforlanguageindependenceoftheimportprocessbyusingstandardizedinterchange
formats.ToallowMoosetoworkwithdifferentbaseandaspectlanguagecombinations,e.g.,toletAspectMapstovisualize
these,itsimplysufficestobeabletoexportthiscodetoacombinationof.mseand.xcrfile.
ToclarifythecreationofboththesefilesandhowthesearejoinedtoformanASPIXmodel,wenowdiscussbothsteps
oftheprocessinmoredetail.
4.2.1. ExportingJavaandAspectJcodeto.mseand.xcrfiles
WehavechosentousethestandardMoose.mseexchangeformat[20]toimportJavacodeintoMoose,yieldingFAMIX
modelinstances.ThisasitallowsustoreuseexistingJavato.mseexporttools,aswellasthestandardMoosefileimport
feature.AssaidinSection3.2,whenloadinginsoftwaretobevisualizedtheAspectMapstoolcanautomaticallygeneratea
.msefileusingtheinFusiontoolandanalternativewaytogeneratethemistouseVerveineJ.
To the best of our knowledge, there is however no tool that takes AspectJ code and provides structural information
ofaspectsandjoinpointshadowinformation.Neitherareweawareofanystandardfileformatforthisinformation.We
thereforebuiltourownexporttoolanddefinedastraightforwardfileformat.AsmentionedinSection3.2,thetoolwe
builtisanEclipseplugin,calledXCutReport.Whenactive,itusesAJDT[7]toproducean.xcrfilewheneverAspectJcodeis
compiled.XCutReporthooksintoAJDTtoreceiveanotificationwhenevercompilationendssuccessfully.Thisnotification
includesacompletestructuralmodeloftheprogramthatwascompiled.Thepluginthentraversesthisstructuralmodel,
writingtherelevantdatatothecorresponding.xcrfile.
Thestructureofan.xcrfileisaself-describinglistoftuples,whereeachtupleistab-delimitedandseparatedfromthe
nexttuplebyanewline.Tuplesaregroupedaccordingtothenatureoftheelementtheydescribeandgroupsareseparated
byanemptyline.Thefirsttwolinesofatuplegroupdescribethegroupasfollows:atitlelinedescribesthenatureofthe
groupandadescriptionlinestatesthestructureofthetuples,i.e.,thesemanticsofeachfield.Thisfileformatwaschosen
becauseitisstraightforwardtoparsewhenimporting,andmoreoveritcanbeeasilyreadwhenopenedbyaspreadsheet
application(byimportingastab-separatedtext).
Forexample,inFig.12weshowpartofthetuplegroupofjoinpointshadowsoftheSpacewarexample(witheachtuple
wrappedtofitthesizeofthepage).Theexampleshowsthatforjoinpointshadows,tuplescontainthenameofandline
numberintheadvisedclass,thetypeofjoinpoint,thenameoftheaspectandlinenumberoftheadvice,aswellaswhether
theshadowpointhasruntimetests.Forcalljoinpoints,thesignatureofthecallaswellasthesourcecodeincludingthecall
(Callsourcecode)arealsoreported.