计算机专业论文译文Spring框架Word格式.docx

计算机专业论文译文Spring框架Word格式.docx

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TheORMpackageprovidesintegrationlayersforpopularobject-relationalmappingAPIs,includingJDO,HibernateandiBatis.UsingtheORMpackageyoucanuseallthoseO/R-mappersincombinationwithalltheotherfeaturesSpringoffers,likesimpledeclarativetransactionmanagementmentionedbefore.

Spring'

sAOPpackageprovidesanAOPAlliancecompliantaspect-orientedprogrammingimplementationallowingyoutodefine,forexample,method-interceptorsandpointcutstocleanlydecouplecodeimplementingfunctionalitythatshouldlogicallyspeakingbeseparated.Usingsource-levelmetadatafunctionalityyoucanincorporateallkindsofbehavioralinformationintoyourcode,alittlelike.NETattributes.

sWebpackageprovidesbasicweb-orientedintegrationfeatures,suchasmultipartfunctionality,initializationofcontextsusingservletlistenersandaweb-orientedapplicationcontext.WhenusingSpringtogetherwithWebWorkorStruts,thisisthepackagetointegratewith.

sWebMVCpackageprovidesaModel-View-Controllerimplementationforweb-applications.Spring'

sMVCimplementationisnotjustanyimplementation,itprovidesacleanseparationbetweendomainmodelcodeandwebformsandallowsyoutousealltheotherfeaturesoftheSpringFrameworklikevalidation.

swebMVCframeworkisdesignedaroundaDispatcherServletthatdispatchesrequeststohandlers,withconfigurablehandlermappings,viewresolution,localeandthemeresolutionaswellassupportforuploadfiles.ThedefaulthandlerisaverysimpleControllerinterface,justofferingaModelAndViewhandleRequest（request,response）method.Thiscanalreadybeusedforapplicationcontrollers,butyouwillprefertheincludedimplementationhierarchy,consistingof,forexampleAbstractController,AbstractCommandControllerandSimpleFormController.Applicationcontrollerswilltypicallybesubclassesofthose.Notethatyoucanchooseanappropriatebaseclass:

Ifyoudon'

thaveaform,youdon'

tneedaFormController.ThisisamajordifferencetoStruts.

Youcanuseanyobjectasacommandorformobject-there'

snoneedtoimplementaninterfaceorderivefromabaseclass.Spring'

sdatabindingishighlyflexible,forexample,ittreatstypemismatchesasvalidationerrorsthatcanbeevaluatedbytheapplication,notassystemerrors.Soyoudon'

tneedtoduplicateyourbusinessobjects'

propertiesasStringsinyourformobjects,justtobeabletohandleinvalidsubmissions,ortoconverttheStringsproperly.Instead,itisoftenpreferabletobinddirectlytoyourbusinessobjects.ThisisanothermajordifferencetoStrutswhichisbuiltaroundrequiredbaseclasseslikeActionandActionForm-foreverytypeofaction.

ComparedtoWebWork,Springhasmoredifferentiatedobjectroles.ItsupportsthenotionofaController,anoptionalcommandorformobject,andamodelthatgetspassedtotheview.Themodelwillnormallyincludethecommandorformobjectbutalsoarbitraryreferencedata.Instead,aWebWorkActioncombinesallthoserolesintoonesingleobject.WebWorkdoesallowyoutouseexistingbusinessobjectsaspartofyourform,butonlybymakingthembeanpropertiesoftherespectiveActionclass.Finally,thesameActioninstancethathandlestherequestisusedforevaluationandformpopulationintheview.Thus,referencedataneedstobemodeledasbeanpropertiesoftheActiontoo.Thesearearguablytoomanyrolesforoneobject.

sviewresolutionisextremelyflexible.AControllerimplementationcanevenwriteaviewdirectlytotheresponse,returningnullasModelAndView.Inthenormalcase,aModelAndViewinstanceconsistsofaviewnameandamodelMap,containingbeannamesandcorrespondingobjects（likeacommandorform,containingreferencedata）.Viewnameresolutionishighlyconfigurable,eitherviabeannames,viaapropertiesfile,orviayourownViewResolverimplementation.TheabstractmodelMapallowsforcompleteabstractionoftheviewtechnology,withoutanyhassle.Anyrenderercanbeintegrateddirectly,whetherJSP,Velocity,oranyotherrenderingtechnology.ThemodelMapissimplytransformedintoanappropriateformat,suchasJSPrequestattributesoraVelocitytemplatemodel..

PluggabilityofotherMVCimplementations

ThereareseveralreasonswhysomeprojectswillprefertouseotherMVCimplementations.Manyteamsexpecttoleveragetheirexistinginvestmentinskillsandtools.Inaddition,thereisalargebodyofknowledgeandexperienceavalailablefortheStrutsframework.Thus,ifyoucanlivewithStruts'

architecturalflaws,itcanstillbeaviablechoicefortheweblayer.ThesameappliestoWebWorkandotherwebMVCframeworks.

Ifyoudon'

twanttouseSpring'

swebMVC,butintendtoleverageothersolutionsthatSpringoffers,youcanintegratethewebMVCframeworkofyourchoicewithSpringeasily.SimplystartupaSpringrootapplicationcontextviaitsContextLoaderListener,andaccessitviaitsServletContextattribute（orSpring'

srespectivehelpermethod）fromwithinaStrutsorWebWorkaction.Notethattherearen'

tany"

plugins"

involved,sonodedicatedintegrationisnecessary.Fromtheweblayer'

spointofview,you'

llsimplyuseSpringasalibrary,withtherootapplicationcontextinstanceastheentrypoint.

AllyourregisteredbeansandallofSpring'

sservicescanbeatyourfingertipsevenwithoutSpring'

swebMVC.Springdoesn'

tcompetewithStrutsorWebWorkinthisscenario,itjustaddressesthemanyareasthatthepurewebMVCframeworksdon'

t,frombeanconfigurationtodataaccessandtransactionhandling.SoyouareabletoenrichyourapplicationwithaSpringmiddletierand/ordataaccesstier,evenifyoujustwanttouse,forexample,thetransactionabstractionwithJDBCorHibernate.

FeaturesofSpringMVC

swebmoduleprovidesawealthofuniquewebsupportfeatures,including:

Clearseparationofroles-controller,validator,commandobject,formobject,modelobject,DispatcherServlet,handlermapping,viewresolver,etc.Eachrolecanbefulfilledbyaspecializedobject.

PowerfulandstraightforwardconfigurationofbothframeworkandapplicationclassesasJavaBeans,includingeasyreferencingacrosscontexts,suchasfromwebcontrollerstobusinessobjectsandvalidators.

Adaptability,non-intrusiveness.Usewhatevercontrollersubclassyouneed（plain,command,form,wizard,multi-action,oracustomone）foragivenscenarioinsteadofderivingfromasinglecontrollerforeverything.

Reusablebusinesscode-noneedforduplication.Youcanuseexistingbusinessobjectsascommandorformobjectsinsteadofmirroringtheminordertoextendaparticularframeworkbaseclass.

Customizablebindingandvalidation-typemismatchesasapplication-levelvalidationerrorsthatkeeptheoffendingvalue,localizeddateandnumberbinding,etcinsteadofString-onlyformobjectswithmanualparsingandconversiontobusinessobjects.

Customizablehandlermappingandviewresolution-handlermappingandviewresolutionstrategiesrangefromsimpleURL-basedconfiguration,tosophisticated,purpose-builtresolutionstrategies.ThisismoreflexiblethansomewebMVCframeworkswhichmandateaparticulartechnique.

Flexiblemodeltransfer-modeltransferviaaname/valueMapsupportseasyintegrationwithanyviewtechnology.

Customizablelocaleandthemeresolution,supportforJSPswithorwithoutSpringtaglibrary,supportforJSTL,supportforVelocitywithouttheneedforextrabridges,etc.

AsimplebutpowerfultaglibrarythatavoidsHTMLgenerationatanycost,allowingformaximumflexibilityintermsofmarkupcode.

DataAccessusingO/RMappers

SpringprovidesintegrationwithHibernate,JDO,OracleTopLink,ApacheOJBandiBATISSQLMaps:

intermsofresourcemanagement,DAOimplementationsupport,andtransactionstrategies.ForexampleforHibernate,thereisfirst-classsupportwithlotsofIoCconveniencefeatures,addressingmanytypicalHibernateintegrationissues.AllofthesesupportpackagesforO/RmapperscomplywithSpring'

sgenerictransactionandDAOexceptionhierarchies.Thereareusuallytwointegrationstyles:

eitherusingSpring'

sDAO'

templates'

orcodingDAOsagainstplainHibernate/JDO/TopLink/etcAPIs.Inbothcases,DAOscanbeconfiguredthroughDependencyInjectionandparticipateinSpring'

sresourceandtransactionmanagement.

saddssignificantsupportwhenusingtheO/Rmapp