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应用技术学院06计算机科学与技术（0616403057）傅晓燕

（外文文件名：

JSPSplittingforImprovingExecutionPerformance）

Abstract

SplittingaJSP（JavaServerPages）pageintofragmentscanimprovetheexecutionperformanceofJSPpageswhentheWebapplicationservercanseparatelycachetheWebpagefragmentsobtainedbyexecutingtheJSPfragments.IfaJSPpageissplitintofragmentsaccordingtotheupdatefrequencyofeachportionoftheWebpageobtainedbyexecutingtheJSPpage,allofthesplitJSPfragmentsdonotneedtobeexecutedagainwhenonlyasinglecachedpartofaWebpageexpires.Inaddition,thefragmentsofaJSPpagecanbereusedbyotherJSPpages.Inbothcases,theexecutionresultsofalloftheJSPfragmentssplitfromtheJSPpagemustbethesameasfromtheJSPpagebeforeitwassplit.Inthispaper,weproposeJSPsplitting,whichisamethodofsplittingaJSPpageintofragmentsmaintainingthedataandcontroldependencesexistingintheoriginalJSPpage.JSPsplittingautomaticallydetectstheportionsneededtomaintainthedataandcontroldependencesofaJSPpagefortheportionsthatdeveloperswanttosplitfromtheJSPpage.WeimplementedJSPsplittingwithaGUItool,andconfirmedthatthesplitJSPfragmentswereexecutedinthesameasthewayastheJSPpagebeforethesplit.ExperimentalresultsshowthattheresponsetimetoaccessaWebpagecanbereducedbysplittingaJSPpageintofragmentsandsettingdifferentcachingperiodsfortheWebpagefragmentsobtainedbyexecutingtheJSPfragments.

1.Introduction

SplittingaJSP（JavaServerPages）pageintofragmentscanimprovetheexecutionperformanceofsomeJSPpageswhentheWebapplicationservercanseparatelycachetheWebpagefragmentsobtainedbyexecutingthefragmentsoftheJSPpage.TheperiodofcachingdynamicWebpagesgeneratedbyaJSPengineislimitedduetothedynamicnatureofthecontent.WhenthecachedcontentofaWebpagegeneratedbyaJSPengineisupdated,theentireJSPpagemustbeexecutedagainontheapplicationserver,eventhoughthechangeoftheWebpagemightbesmall.SincefrequentupdatesofcachedWebpagesincreasetheloadonanapplicationserver,itisreasonabletosplitaJSPpageintofragmentsandsetdifferentcachingperiodsfortheWebpagefragmentsobtainedbyexecutingtheJSPfragments.Ofcourse,theWebpagefragmentsmustbemergedintoafinalWebpagecorrectly.TheDynacachetechnologyofIBMWebSphereApplicationServerallowsWebpagefragmentstohavedifferentcachingperiods.CachetaglibrariesprovidedbytheApacheJakartaProjectalsosupportdifferentcachingperiodsfortheJSPfragments.Inaddition,ESI（EdgeSideIncludes）technologyprovidesamechanismtocacheWebpagefragmentswithdifferentcachingperiods,andtomergethemintoafinalWebpageonanedgeserver.

TheapplicationoffloadtechnologyofIBMWebSphereEdgeServerisanotherapproachtoimprovetheexecutionperformanceofJSPpages.ThistechnologyallowsoneormoreJSPfragmentstobecachedandexecutedonedgeservers.TheremainingJSPfragmentsaredeployedontheapplicationserverandarecalledbytheJSPfragmentsexecutedontheedgeserver.Thus,someoftheexecutionofaJSPpageisoffloadedtotheedgeserver.

SplittingaJSPpagefacilitatesthereuseofJSPfragments.WhenaWebapplicationconsistsofmanyJSPpages,thesameportionstendtoexistinmanyJSPpages.Examplesaretheframes,thebanners,theheaders,andetc.

WhenaJSPpageissplitintofragments,thetotalexecutionresultofallofthefragmentsmustbethesameastheJSPpagebeforeitwassplit.Inaddition,whenthefragmentsofaJSPpageareexecutedindifferentservers,eachfragmentneedstobeexecutedwithouttheotherfragments.Inordertosatisfytheseconditions,weproposeJSPsplitting,whichisthemethodofsplittingaJSPpageintofragmentsdescribedinthispaper.SinceitisverydifficulttoautomaticallyfindthebestwaytosplitaJSPpageintofragmentsforsomeparticularpurpose,weassumethatthedeveloperswillselecttheportionsthattheywanttosplitintofragments.InordertoexecuteallofthedividedJSPpagescorrectly,JSPsplittingautomaticallydetectsanyportionsthatmustbemovedorcopiedintoafragmentwiththeselectedportions.ThedetectionisdonebasedontheanalysisofthedataandcontroldependencesexistinginaJSPpage.JSPsplittingissimilartotheprogramslicingtechniquethatslicesaprogrambasedonthedataandthecontroldependences.However,theprogramslicingtechniquedoesnottakeintoaccountthattheslicedprogramsareexecutedindependentlyandthatthetotalexecutionresultoftheslicedprogramsmustbethesameastheprogrambeforethedivision.Inaddition,sincedataispassedtotheJSPengineduringtheexecutionofJSPpages,thesourceprogramoftheJSPengine,suchasApacheTomcat,isrequiredinordertoanalyzethedatadependencescorrectly.Thisisimpractical,becausethesourceprogramoftheJSPengineisverylargeandcomplex.JSPsplittingavoidstheanalysisoftheJSPenginebyutilizingthecharacteristicsofJSP.

Therestofthepaperisorganizedasfollows.Section2explainsthedifficultyofsplittingaJSPpageintofragments.Section3givesdetailsofthealgorithmtosplitaJSPpage.Section4describestheJSPsplittingtoolthatisanimplementationofJSPsplittinganddemonstrateshowasampleJSPpageissplitbythetool.Section5showstheexperimentalresultsobtainedbyexecutingthesplitJSPfragmentswithdifferentcachingperiodsontheIBMWebSphereApplicationServer.Section6discussespreviousworkinrelationtoourcontributions.Ourconclusionsformthefinalsection.

2.DifficultyofSplittingaJSPPage

Inthispaper,splittingaJSPpagemeansthatsomeportionsoftheJSPpagearecutfromtheJSPpageandsavedasnewJSPpages.SuchnewlycreatedJSPpagesareincludedintheoriginalJSPpagebyusingsomemechanismsuchasthejsp:

includetag.WecalltheincludedJSPpagetheJSPfragment,andcalltheJSPpagethatinvokestheJSPfragmentsthemasterJSPpage.AmasterJSPpageinvokesJSPfragmentsandreceivesWebpagefragmentsobtainedbyexecutingthem.ThenthemasterJSPpagemergesitsownWebpagefragmentwiththeWebpagefragmentsreceivedfromtheJSPfragments,andcreatesafinalWebpage.

JSPfragmentsarenotalwaysexecutedinthesameserveroratthesametime.TheapplicationoffloadtechnologyallowsamasterJSPpageandJSPfragmentstobeexecutedindifferentservers.WhentheESImechanismisused,esi:

includetagsareputintoaWebpagefragmentobtainedbyexecutingamasterJSPpageandinterpretedinanedgeserverthatsupportstheESImechanism.Inthiscase,theedgeservercheckswhetherornottheWebpagefragmentsspecifiedbyesi:

includetagsexistinitscache.IfthecontentsofWebpagefragmentsarenotcachedorhaveexpired,theJSPfragmentsareinvokedfromtheedgeserver,andexecutedinoneormoreapplicationservers.IfdifferentcachingperiodscanbegiventotheWebpagefragmentsobtainedbyexecutingtheJSPfragments,eachJSPfragmentisexecutedonlywhenthecachedcontenthasexpired.TheDynacachetechnology,theESImechanism,andthecachetaglibrariescansupportdifferentcachingperiodsforWebpagefragments.

WhenaJSPpageissplitintofragments,thefollowingtwoconditionsmustbesatisfiedevenifthemasterJSPpageandtheJSPfragmentsarenotexecutedinthesameserveroratthesametime.

Cond.1-1ThetotalexecutionresultofamasterJSPpageandtheJSPfragmentsisthesameastheJSPpagebeforeitwassplit.

Cond.1-2EachJSPpage,whichiseitheramasterJSPpageoraJSPfragment,maybeexecutedwithoutotherJSPpages.

TheseconditionsaresatisfiedbymaintainingthedataandcontroldependencesexistinginaJSPpageaftertheJSPpagehasbeensplitintofragments.However,itishardworkfordeveloperstodetectdataandcontroldependentportionsinaJSPpage,becausethedataandcontrolflowofaJSPpagecanbedividedamongtheJSPpage,theJSPenginethatexecutestheJSPpage,anyJavabeansusedintheJSPpage,andetc..Thus,anaturalsolutioncallsforautomaticallydetectingdata-dependentandcontrol-dependentportionslinkedtotheportionsthatdeveloperswanttosplit.

TheprogramslicingtechniquedetectsasetofprogramstatementsthataffectaprogramstatementSbyanalyzingthedataandcontroldependencesexistingintheprogram.OneprogramsliceconsistsofthedetectedsetofprogramstatementsandthestatementS.Thistechniqueisusefulwhendebuggingormaintaininglargeprograms.SinceJSPpagesarecompiledintoservletprogramsbyusingaJSPcompilersuchastheApacheJaspercompiler[4],JSPslicescanbeobtainedbyapplyingprogramslicingtechniquetoaservletprogramcompiledfromaJSPpage.However,theprogramslicingtechniqueisnotsufficienttosplitaJSPpageintofragments,becausethetechniquedoesnottakeintoaccountthatprogramslicesareexecutedindependently.

Figure1showsapartofasampleJSPpageandasampleservletprogramcompiledfromtheJSPpage.Figure2（a）showsthedatadependencegraphobtainedfromtheservletprogram.Inaprogram,whenastatementS1assignsavaluetoavariableandastatementS2followingS1usesthatvalue,atruedatadependenceexistsbetweenS1andS2.SuchadatadependenceisdenotedasS1S2.InFigure2（a）,duetothedatadependences,theprogramsliceforthestatementS10consistsofS1,S9,andS10.Iftheprogramsliceiscutfromtheservletprogram,theremainingprogramstatementshaveerrorsbecausethedatadependencesS1S2,S11,andS12andS9S11a