基于net外文翻译.docx

基于net外文翻译.docx

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基于net外文翻译

专业外文翻译

题目

基于J2EE在分布式环境下的

底层结构的自动动态配置的应用

系（院）

专业

班级

学生姓名

学号

指导教师

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滨州学院教务处

二〇一〇年三月一日

InfrastructureforAutomaticDynamicDeploymentOfJ2EEApplicationinDistributedEnvironments

AnatolyAkkerman,AlexanderTotok,andVijayKaramcheti

1.Introduction

Inrecentyears,wehaveseenasignificantgrowthincomponent-basedenterpriseapplicationdevelopment.TheseapplicationsaretypicallydeployedoncompanyIntranetsorontheInternetandarecharacterizedbyhightransactionvolume,largenumbersofusersandwideareaaccess.Traditionallytheyaredeployedinacentrallocation,usingserverclusteringwithloadbalancing（horizontalpartitioning）tosustainuserload.However,horizontalpartitioninghasbeenshownveryefficientonlyinreducingapplication-relatedoverheadsofuser-perceivedresponsetimes,withouthavingmucheffectonnetwork-inducedlatencies.Verticalpartitioning（e.g.,runningwebtierandbusinesstierinseparateVMs）hasbeenusedforfaultisolationandloadbalancingbutitissometimesimpracticalduetosignificantrun-timeoverheads（evenifonewouldkeepthetiersonafastlocal-areanetwork）relatedtoheavyuseofremoteinvocations.RecentworkinthecontextofJ2EEcomponentbasedapplicationshasshownviabilityofverticalpartitioninginwide-areanetworkswithoutincurringtheaforementionedoverheads.Thekeyconclusionsfromthatstudycanbesummarizedasfollows:

•Usingproperlydesignedapplications,verticaldistributionacrosswide-areanetworksimprovesuser-perceivedlatencies.

•Wide-areaverticallayeringrequiresreplicationofapplicationcomponentsandmaintainingconsistencybetweenreplicas.

•Additionalreplicasmaybedeployeddynamicallytohandlenewrequests.

•Differentreplicasmay,infact,bedifferentimplementationsofthesamecomponentbasedonusage（read-only,read-write）.

•Newrequestpathsmayreusecomponentsfrompreviouslydeployedpaths.

ApplyingintelligentmonitoringandAIplanningtechniquesinconjunctionwiththeconclusionsofthatstudy,weseeapotentialfordynamicadaptationinindustry-standardJ2EEcomponent-basedapplicationsinwideareanetworks

Throughdeploymentofadditionalapplicationcomponentsdynamicallybasedonactivemonitoring.However,inordertoachievesuchdynamicadaptation,weneedaninfrastructureforautomatingJ2EEapplicationdeploymentinsuchanenvironment.ThisneedisquiteevidenttoanyonewhohasevertrieddeployingaJ2EEapplicationevenonasingleapplicationserver,whichisataskthatinvolvesagreatdealofconfigurationofboththesystemservicesandapplicationcomponents.ForexampleonehastosetupJDBCdatasources,messagingdestinationsandotherresourceadaptersbeforeapplicationcomponentscanbeconfiguredanddeployed.Inawideareadeploymentthatspansmultipleservernodes,thisprovesevenmorecomplex,sincemoresystemservicesthatfacilitateinter-nodecommunicationsneedtobeconfiguredandstartedandavarietyofconfigurationdata,likeIPaddresses,portnumbers,JNDInamesandothershavetobeconsistentlymaintainedinvariousconfigurationfilesonmultiplenodes.

Thisdistributeddeploymentinfrastructuremustbeableto:

•addressinter-componentconnectivityspecificationanddefineitseffectsoncomponentconfigurationanddeployment,

•addressapplicationcomponentdependenciesonapplicationserverservices,theirconfigurationanddeployment,

•providesimplebutexpressiveabstractionstocontroladaptationthroughdynamicdeploymentandundeploymentofcomponents,

•enablereuseofservicesandcomponentstomaintainefficientuseofnetworknodes’resources,

•providethesefacilitieswithoutincurringsignificantadditionaldesigneffortonbehalfofapplicationprogrammers.

InthispaperweproposetheinfrastructureforautomaticdynamicdeploymentofJ2EEapplications,whichaddressesalloftheaforementionedissues.Theinfrastructuredefinesarchitecturedescriptionlanguages（ADL）forcomponentandlinkdescriptionandassembly.TheComponentDescriptionLanguageisusedtodescribeapplicationcomponentsandlinks.Itprovidesclearseparationofapplicationcomponentsfromsystemcomponents.Aflexibletypesystemisusedtodefinecompatibilityofcomponentportsandlinks.Adeclarationandexpressionlanguageforconfigurablecomponentpropertiesallowsforspecificationofinter-componentdependenciesandpropagationofpropertiesbetweencomponents.TheComponent（Replica）AssemblyLanguageallowsforassemblyofreplicasofpreviouslydefinedcomponentsintoapplicationpathsbyconnectingappropriateportsvialinkreplicasandspecifyingthemappingofthesecomponentreplicasontotargetapplicationservernodes.TheComponentConfigurationProcessevaluatesanapplicationpath’scorrectness,identifiesthedependenciesofapplicationcomponentsonsystemcomponents,andconfigurescomponentreplicasfordeployment.Anattemptismadetomatchandreuseanypreviouslydeployedreplicasinthenewpathbasedontheirconfigurations.WeimplementtheinfrastructureasapartoftheJBossopensourceJavaapplicationserverandtestitonseveraltechnologysampleJ2EEapplications–JavaPetstore,RubiesandTPC-W-NYU.TheinfrastructureimplementationutilizestheJBoss’sextendablemicro-kernelarchitecture,basedontheJMXspecification.ComponentizedarchitectureofJBossallowsincrementalservicedeploymentsdependingontheneedsofdeployedapplications.Webelievethatdynamicreconfigurationofapplicationserversthroughdynamicdeploymentandundeploymentofsystemservicesisessentialtobuildingaresource-efficientframeworkfordynamicdistributeddeploymentofJ2EEapplications.Therestofthepaperisorganizedasfollows.Section2providesnecessarybackgroundforunderstandingthespecificsoftheJ2EEcomponenttechnologywhicharerelevanttothisstudy.Section3givesageneraldescriptionoftheinfrastructurearchitecture,whilesection4goesdeeperindescribingparticularlyimportantandinterestinginternalmechanismsoftheinfrastructure.Section5describestheimplementationoftheframework,andrelatedworkisdiscussedinsection6.

2.J2EEBackground

2.1Introduction

Componentframeworks.

Acomponentframeworkisamiddlewaresystemthatsupportsapplicationsconsistingofcomponentsconformingtocertainstandards.Applicationcomponentsare“plugged”intothecomponentframework,whichestablishestheirenvironmentalconditionsandregulatestheinteractionsbetweenthem.Thisisusuallydonethroughcontainers,componentholders,whichalsoprovidecommonlyrequiredsupportfornaming,security,transactions,andpersistence.Componentframeworksprovideanintegratedenvironmentforcomponentexecution,asaresultsignificantlyreducetheeffort.ittakestodesign,implement,deploy,andmaintainapplications.CurrentdayindustrycomponentframeworkstandardsarerepresentedbyObjectManagementGroup’sCORBAComponentModel,SunMicrosystems’Java2PlatformEnterpriseEdition（J2EE）andMicrosoft’s.NET,withJ2EEbeingcurrentlythemostpopularandwidelyusedcomponentframeworkintheenterprisearena.

J2EE.

Java2PlatformEnterpriseEdition（J2EE）isacomprehensivestandardfordevelopingmulti-tierenterpriseJavaapplications.TheJ2EEspecificationamongotherthingsdefinesthefollowing:

•Componentprogrammingmodel,

•Componentcontractswiththehostingserver,

•Servicesthattheplatformprovidestothesecomponents,

•Varioushumanroles,

•Compatibilitytestsuitesandcompliancetestingprocedures.

Amongthelistofservicesthatacompliantapplicationservermustprovidearemessaging,transactions,namingandothersthatcanbeusedbytheapplicationcomponents.ApplicationdevelopedusingJ2EEadheretotheclassical3-Tierarchitectures–PresentationTier,BusinessTier,andEnterpriseInformationSystem（EIS）Tier（seeFig.1）.J2EEcomponentsbelongingtoeachtieraredevelopedadheringtothe

SpecificJ2EEstandards.

1.PresentationorWebtier.

Thistierisactuallysubdividedintoclientandserversides.Theclientsidehostsawebbrowser,appletsandJavaapplicationsthatcommunicatewiththeserversideofpresentationtierorthebusinesstier.TheserversidehostsJavaServletcomponents,JavaServerPages（JSPs）andstaticwebcontent.Thesecomponentsareresponsibleforpresentingbusinessdatatotheendusers.ThedataitselfistypicallyacquiredfromthebusinesstierandsometimesdirectlyfromtheEnterpriseInformationSystemtier.TheserversideofthepresentationtieristypicallyaccessedthroughHTTP（S）protocol.

2.BusinessorEJBtier.

ThistierconsistsofEnterpriseJavaBeans（EJBs）thatmodelthebusinesslogicoftheenterpriseapplication.Thesecomponentsprovidepersistencemechanismsandtransactionalsupport.ThecomponentsintheEJBtierareinvokedthroughremoteinvocations（RMI）,in-JVMinvocationsorasynchronousmessagedelivery,dependingonthetypeofEJBcomponent.TheEJBspecificationdefinesseveraltypesofcomponents.Theydifferininvocationstyle（synchronousvs.asynchronous,localvs.remote）andstatefulness:

completelystateless（e.g.,Message-DrivenBean）,statefulnon-persistent

（e.g.,StatefulSessionBean）,statefulpersistent（e.g.,EntityBean）.SynchronouslyinvocableEJBcomponentsexposethemselvesthroughaspecialfactoryproxyobject（anEJBHomeobject,whichisspecifictoagivenEJB）,whichistypicallyboundinJNDIbythedeployeroftheEJB.TheEJBHomeobjectallowscreationorlocationofanEJBObject,whichisaproxytoaparticularinstanceofanEJB1.

3.EnterpriseInformationSystem（EIS）orDatatier.

Thistierreferstotheenterpris