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xxxx大学xxx学院
毕业设计(论文)外文文献翻译
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指导教师
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2013年3月
IntroducingtheSpringFramework
TheSpringFramework:
apopularopensourceapplicationframeworkthataddressesmanyoftheissuesoutlinedinthisbook.ThischapterwillintroducethebasicideasofSpringanddis-cussthecentral“beanfactory”lightweightInversion-of-Control(IoC)containerindetail.
Springmakesitparticularlyeasytoimplementlightweight,yetextensible,J2EEarchi-tectures.Itprovidesanout-of-the-boximplementationofthefundamentalarchitecturalbuildingblockswerecommend.Springprovidesaconsistentwayofstructuringyourapplications,andprovidesnumerousmiddletierfeaturesthatcanmakeJ2EEdevelopmentsignificantlyeasierandmoreflexiblethanintraditionalapproaches.
ThebasicmotivationsforSpringare:
Toaddressareasnotwellservedbyotherframeworks.TherearenumerousgoodsolutionstospecificareasofJ2EEinfrastructure:
webframeworks,persistencesolutions,remotingtools,andsoon.However,integratingthesetoolsintoacomprehensivearchitecturecaninvolvesignificanteffort,andcanbecomeaburden.Springaimstoprovideanend-to-endsolution,integratingspe-cializedframeworksintoacoherentoverallinfrastructure.Springalsoaddressessomeareasthatotherframeworksdon’t.Forexample,fewframeworksaddressgenerictransactionmanagement,dataaccessobjectimplementation,andgluingallthosethingstogetherintoanapplication,whilestillallowingforbest-of-breedchoiceineacharea.HencewetermSpringanapplicationframework,ratherthanawebframework,IoCorAOPframework,orevenmiddletierframework.
Toallowforeasyadoption.Aframeworkshouldbecleanlylayered,allowingtheuseofindi-vidualfeatureswithoutimposingawholeworldviewontheapplication.ManySpringfeatures,suchastheJDBCabstractionlayerorHibernateintegration,canbeusedinalibrarystyleoraspartoftheSpringend-to-endsolution.
Todelivereaseofuse.Aswe’venoted,J2EEoutoftheboxisrelativelyhardtousetosolvemanycommonproblems.Agoodinfrastructureframeworkshouldmakesimpletaskssimpletoachieve,withoutforcingtradeoffsforfuturecomplexrequirements(likedistributedtransactions)ontheapplicationdeveloper.ItshouldallowdeveloperstoleverageJ2EEservicessuchasJTAwhereappropriate,buttoavoiddependenceonthemincaseswhentheyareunnecessarilycomplex.
Tomakeiteasiertoapplybestpractices.Springaimstoreducethecostofadheringtobestpracticessuchasprogrammingtointerfaces,ratherthanclasses,almosttozero.However,itleavesthechoiceofarchitecturalstyletothedeveloper.
Non-invasiveness.Applicationobjectsshouldhaveminimaldependenceontheframework.IfleveragingaspecificSpringfeature,anobjectshoulddependonlyonthatparticularfeature,whetherbyimplementingacallbackinterfaceorusingtheframeworkasaclasslibrary.IoCandAOParethekeyenablingtechnologiesforavoidingframeworkdependence.
Consistentconfiguration.Agoodinfrastructureframeworkshouldkeepapplicationconfigurationflexibleandconsistent,avoidingtheneedforcustomsingletonsandfactories.Asinglestyleshouldbeapplicabletoallconfigurationneeds,fromthemiddletiertowebcontrollers.
Easeoftesting.Testingeitherwholeapplicationsorindividualapplicationclassesinunittestsshouldbeaseasyaspossible.Replacingresourcesorapplicationobjectswithmockobjectsshouldbestraightforward.
Toallowforextensibility.BecauseSpringisitselfbasedoninterfaces,ratherthanclasses,itiseasytoextendorcustomizeit.ManySpringcomponentsusestrategyinterfaces,allowingeasycustomization.
ALayeredApplicationFramework
Chapter6introducedtheSpringFrameworkasalightweightcontainer,competingwithIoCcontainerssuchasPicoContainer.WhiletheSpringlightweightcontainerforJavaBeansisacoreconcept,thisisjustthefoundationforasolutionforallmiddlewarelayers.
BasicBuildingBlocks
pringisafull-featuredapplicationframeworkthatcanbeleveragedatmanylevels.Itconsistsofmulti-plesub-frameworksthatarefairlyindependentbutstillintegratecloselyintoaone-stopshop,ifdesired.Thekeyareasare:
Beanfactory.TheSpringlightweightIoCcontainer,capableofconfiguringandwiringupJava-BeansandmostplainJavaobjects,removingtheneedforcustomsingletonsandadhocconfigura-tion.Variousout-of-the-boximplementationsincludeanXML-basedbeanfactory.ThelightweightIoCcontaineranditsDependencyInjectioncapabilitieswillbethemainfocusofthischapter.
Applicationcontext.ASpringapplicationcontextextendsthebeanfactoryconceptbyaddingsupportformessagesourcesandresourceloading,andprovidinghooksintoexistingenv