畢業(yè)設計外文文獻-Spring Web MVC

畢業(yè)設計(論文)外文資料翻譯外文出處:https://docs.spring.io/spring/docs/current/spring-framework-reference/web.html附件：A.外文翻譯-原文部分B.外文翻譯-譯文部分

附錄A.外文翻譯-原文部分FROM:https://docs.spring.io/spring/docs/current/spring-framework-reference/web.htmlSpringWebMVCSpringWebMVCistheoriginalwebframeworkbuiltontheServletAPIandhasbeenincludedintheSpringFrameworkfromtheverybeginning.Theformalname,“SpringWebMVC,”comesfromthenameofitssourcemodule(spring-webmvc),butitismorecommonlyknownas“SpringMVC”.1.1.DispatcherServletSameasinSpringWebFluxSpringMVC,asmanyotherwebframeworks,isdesignedaroundthefrontcontrollerpatternwhereacentral

Servlet,the

DispatcherServlet,providesasharedalgorithmforrequestprocessing,whileactualworkisperformedbyconfigurabledelegatecomponents.Thismodelisflexibleandsupportsdiverseworkflows.The

DispatcherServlet,asany

Servlet,needstobedeclaredandmappedaccordingtotheServletspecificationbyusingJavaconfigurationorin

web.xml.Inturn,the

DispatcherServlet

usesSpringconfigurationtodiscoverthedelegatecomponentsitneedsforrequestmapping,viewresolution,exceptionhandling,

andmore.ThefollowingexampleoftheJavaconfigurationregistersandinitializesthe

DispatcherServlet,whichisauto-detectedbytheServletcontainer(see

ServletConfig):publicclassMyWebApplicationInitializerimplementsWebApplicationInitializer{@OverridepublicvoidonStartup(ServletContextservletCxt){//LoadSpringwebapplicationconfigurationAnnotationConfigWebApplicationContextac=newAnnotationConfigWebApplicationContext();ac.register(AppConfig.class);ac.refresh();//CreateandregistertheDispatcherServletDispatcherServletservlet=newDispatcherServlet(ac);ServletRegistration.Dynamicregistration=servletCxt.addServlet("app",servlet);registration.setLoadOnStartup(1);registration.addMapping("/app/*");}}InadditiontousingtheServletContextAPIdirectly,youcanalsoextendAbstractAnnotationConfigDispatcherServletInitializer

andoverridespecificmethods(seetheexampleunder

ContextHierarchy).Thefollowingexampleof

web.xml

configurationregistersandinitializesthe

DispatcherServlet:<web-app><listener><listener-class>org.springframework.web.context.ContextLoaderListener</listener-class></listener><context-param><param-name>contextConfigLocation</param-name><param-value>/WEB-INF/app-context.xml</param-value></context-param><servlet><servlet-name>app</servlet-name><servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class><init-param><param-name>contextConfigLocation</param-name><param-value></param-value></init-param><load-on-startup>1</load-on-startup></servlet><servlet-mapping><servlet-name>app</servlet-name><url-pattern>/app/*</url-pattern></servlet-mapping></web-app>SpringBootfollowsadifferentinitializationsequence.RatherthanhookingintothelifecycleoftheServletcontainer,SpringBootusesSpringconfigurationtobootstrapitselfandtheembeddedServletcontainer.

Filter

and

Servlet

declarationsaredetectedinSpringconfigurationandregisteredwiththeServletcontainer.Formoredetails,seethe

SpringBootdocumentation.1.1.1.ContextHierarchyDispatcherServlet

expectsa

WebApplicationContext

(anextensionofaplain

ApplicationContext)foritsownconfiguration.

WebApplicationContext

hasalinktothe

ServletContext

andthe

Servlet

withwhichitisassociated.Itisalsoboundtothe

ServletContext

suchthatapplicationscanusestaticmethodson

RequestContextUtils

tolookupthe

WebApplicationContextiftheyneedaccesstoit.Formanyapplications,havingasingle

WebApplicationContext

issimpleandsuffices.Itisalsopossibletohaveacontexthierarchywhereoneroot

WebApplicationContext

issharedacrossmultiple

DispatcherServlet

(orother

Servlet)instances,eachwithitsownchild

WebApplicationContext

configuration.See

AdditionalCapabilitiesofthe?ApplicationContext

formoreonthecontexthierarchyfeature.Theroot

WebApplicationContext

typicallycontainsinfrastructurebeans,suchasdatarepositoriesandbusinessservicesthatneedtobesharedacrossmultiple

Servlet

instances.Thosebeansareeffectivelyinheritedandcanbeoverridden(thatis,re-declared)intheServlet-specificchild

WebApplicationContext,whichtypicallycontainsbeanslocaltothegiven

Servlet.Thefollowingimageshowsthisrelationship:Thefollowingexampleconfiguresa

WebApplicationContext

hierarchy:publicclassMyWebAppInitializerextendsAbstractAnnotationConfigDispatcherServletInitializer{@OverrideprotectedClass<?>[]getRootConfigClasses(){returnnewClass<?>[]{RootConfig.class};}@OverrideprotectedClass<?>[]getServletConfigClasses(){returnnewClass<?>[]{App1Config.class};}@OverrideprotectedString[]getServletMappings(){returnnewString[]{"/app1/*"};}}Ifanapplicationcontexthierarchyisnotrequired,applicationscanreturnallconfigurationthrough

getRootConfigClasses()

and

null

from

getServletConfigClasses().Thefollowingexampleshowsthe

web.xml

equivalent:<web-app><listener><listener-class>org.springframework.web.context.ContextLoaderListener</listener-class></listener><context-param><param-name>contextConfigLocation</param-name><param-value>/WEB-INF/root-context.xml</param-value></context-param><servlet><servlet-name>app1</servlet-name><servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class><init-param><param-name>contextConfigLocation</param-name><param-value>/WEB-INF/app1-context.xml</param-value></init-param><load-on-startup>1</load-on-startup></servlet><servlet-mapping><servlet-name>app1</servlet-name><url-pattern>/app1/*</url-pattern></servlet-mapping></web-app>Ifanapplicationcontexthierarchyisnotrequired,applicationsmayconfigurea“root”contextonlyandleavethe

contextConfigLocation

Servletparameterempty.1.1.2.SpecialBeanTypesSameasinSpringWebFluxThe

DispatcherServlet

delegatestospecialbeanstoprocessrequestsandrendertheappropriateresponses.By“specialbeans”wemeanSpring-managed

Object

instancesthatimplementframeworkcontracts.Thoseusuallycomewithbuilt-incontracts,butyoucancustomizetheirpropertiesandextendorreplacethem.Thefollowingtableliststhespecialbeansdetectedbythe

DispatcherServlet:BeantypeExplanationHandlerMappingMaparequesttoahandleralongwithalistof

interceptors

forpre-andpost-processing.Themappingisbasedonsomecriteria,thedetailsofwhichvaryby

HandlerMapping

implementation.Thetwomain

HandlerMapping

implementationsare

RequestMappingHandlerMapping

(whichsupports

@RequestMapping

annotatedmethods)and

SimpleUrlHandlerMapping

(whichmaintainsexplicitregistrationsofURIpathpatternstohandlers).HandlerAdapterHelpthe

DispatcherServlet

toinvokeahandlermappedtoarequest,regardlessofhowthehandlerisactuallyinvoked.Forexample,invokinganannotatedcontrollerrequiresresolvingannotations.Themainpurposeofa

HandlerAdapteristoshieldthe

DispatcherServlet

fromsuchdetails.HandlerExceptionResolverStrategytoresolveexceptions,possiblymappingthemtohandlers,toHTMLerrorviews,orothertargets.See

Exceptions.ViewResolverResolvelogical

String-basedviewnamesreturnedfromahandlertoanactual

View

withwhichtorendertotheresponse.See

ViewResolution

and

ViewTechnologies.LocaleResolver,

LocaleContextResolverResolvethe

Locale

aclientisusingandpossiblytheirtimezone,inordertobeabletoofferinternationalizedviews.See

Locale.ThemeResolverResolvethemesyourwebapplicationcanuse?—?forexample,toofferpersonalizedlayouts.See

Themes.MultipartResolverAbstractionforparsingamulti-partrequest(forexample,browserformfileupload)withthehelpofsomemultipartparsinglibrary.See

MultipartResolver.FlashMapManagerStoreandretrievethe“input”andthe“output”

FlashMap

thatcanbeusedtopassattributesfromonerequesttoanother,usuallyacrossaredirect.See

FlashAttributes.1.1.3.WebMVCConfigSameasinSpringWebFluxApplicationscandeclaretheinfrastructurebeanslistedin

SpecialBeanTypes

thatarerequiredtoprocessrequests.The

DispatcherServlet

checksthe

WebApplicationContext

foreachspecialbean.Iftherearenomatchingbeantypes,itfallsbackonthedefaulttypeslistedin

DispatcherSperties.Inmostcases,the

MVCConfig

isthebeststartingpoint.ItdeclarestherequiredbeansineitherJavaorXMLandprovidesahigher-levelconfigurationcallbackAPItocustomizeit.SpringBootreliesontheMVCJavaconfigurationtoconfigureSpringMVCandprovidesmanyextraconvenientoptions.1.1.4.ServletConfigInaServlet3.0+environment,youhavetheoptionofconfiguringtheServletcontainerprogrammaticallyasanalternativeorincombinationwitha

web.xml

file.Thefollowingexampleregistersa

DispatcherServlet:importorg.springframework.web.WebApplicationInitializer;publicclassMyWebApplicationInitializerimplementsWebApplicationInitializer{@OverridepublicvoidonStartup(ServletContextcontainer){XmlWebApplicationContextappContext=newXmlWebApplicationContext();appContext.setConfigLocation("/WEB-INF/spring/dispatcher-config.xml");ServletRegistration.Dynamicregistration=container.addServlet("dispatcher",newDispatcherServlet(appContext));registration.setLoadOnStartup(1);registration.addMapping("/");}}WebApplicationInitializer

isaninterfaceprovidedbySpringMVCthatensuresyourimplementationisdetectedandautomaticallyusedtoinitializeanyServlet3container.Anabstractbaseclassimplementationof

WebApplicationInitializernamed

AbstractDispatcherServletInitializer

makesiteveneasiertoregisterthe

DispatcherServlet

byoverridingmethodstospecifytheservletmappingandthelocationofthe

DispatcherServlet

configuration.ThisisrecommendedforapplicationsthatuseJava-basedSpringconfiguration,asthefollowingexampleshows:publicclassMyWebAppInitializerextendsAbstractAnnotationConfigDispatcherServletInitializer{@OverrideprotectedClass<?>[]getRootConfigClasses(){returnnull;}@OverrideprotectedClass<?>[]getServletConfigClasses(){returnnewClass<?>[]{MyWebConfig.class};}@OverrideprotectedString[]getServletMappings(){returnnewString[]{"/"};}}IfyouuseXML-basedSpringconfiguration,youshouldextenddirectlyfrom

AbstractDispatcherServletInitializer,asthefollowingexampleshows:publicclassMyWebAppInitializerextendsAbstractDispatcherServletInitializer{@OverrideprotectedWebApplicationContextcreateRootApplicationContext(){returnnull;}@OverrideprotectedWebApplicationContextcreateServletApplicationContext(){XmlWebApplicationContextcxt=newXmlWebApplicationContext();cxt.setConfigLocation("/WEB-INF/spring/dispatcher-config.xml");returncxt;}@OverrideprotectedString[]getServletMappings(){returnnewString[]{"/"};}}AbstractDispatcherServletInitializer

alsoprovidesaconvenientwaytoadd

Filter

instancesandhavethembeautomaticallymappedtothe

DispatcherServlet,asthefollowingexampleshows:publicclassMyWebAppInitializerextendsAbstractDispatcherServletInitializer{//...@OverrideprotectedFilter[]getServletFilters(){returnnewFilter[]{newHiddenHttpMethodFilter(),newCharacterEncodingFilter()};}}Eachfilterisaddedwithadefaultnamebasedonitsconcretetypeandautomaticallymappedtothe

DispatcherServlet.The

isAsyncSupported

protectedmethodof

AbstractDispatcherServletInitializer

providesasingleplacetoenableasyncsupportonthe

DispatcherServlet

andallfiltersmappedtoit.Bydefault,thisflagissetto

true.Finally,ifyouneedtofurthercustomizethe

DispatcherServlet

itself,youcanoverridethe

createDispatcherServlet

method.1.1.5.ProcessingSameasinSpringWebFluxThe

DispatcherServlet

processesrequestsasfollows:The

WebApplicationContext

issearchedforandboundintherequestasanattributethatthecontrollerandotherelementsintheprocesscanuse.Itisboundbydefaultunderthe

DispatcherServlet.WEB_APPLICATION_CONTEXT_ATTRIBUTE

key.Thelocaleresolverisboundtotherequesttoletelementsintheprocessresolvethelocaletousewhenprocessingtherequest(renderingtheview,preparingdata,andsoon).Ifyoudonotneedlocaleresolving,youdonotneedthelocaleresolver.Thethemeresolverisboundtotherequesttoletelementssuchasviewsdeterminewhichthemetouse.Ifyoudonotusethemes,youcanignoreit.Ifyouspecifyamultipartfileresolver,therequestisinspectedformultiparts.Ifmultipartsarefound,therequestiswrappedina

MultipartHttpServletRequest

forfurtherprocessingbyotherelementsintheprocess.See

MultipartResolver

forfurtherinformationaboutmultiparthandling.Anappropriatehandlerissearchedfor.Ifahandlerisfound,theexecutionchainassociatedwiththehandler(preprocessors,postprocessors,andcontrollers)isexecutedinordertoprepareamodelorrendering.Alternatively,forannotatedcontrollers,theresponsecanberendered(withinthe

HandlerAdapter)insteadofreturningaview.Ifamodelisreturned,theviewisrendered.Ifnomodelisreturned(maybeduetoapreprocessororpostprocessorinterceptingtherequest,perhapsforsecurityreasons),noviewisrendered,becausetherequestcouldalreadyhavebeenfulfilled.The

HandlerExceptionResolver

beansdeclaredinthe

WebApplicationContext

areusedtoresolveexceptionsthrownduringrequestprocessing.Thoseexceptionresolversallowcustomizingthelogictoaddressexceptions.See

Exceptions

formoredetails.TheSpring

DispatcherServlet

alsosupportsthereturnofthe

last-modification-date,asspecifiedbytheServletAPI.Theprocessofdeterminingthelastmodificationdateforaspecificrequestisstraightforward:The

DispatcherServlet

looksupanappropriatehandlermappingandtestswhetherthehandlerthatisfoundimplementsthe

LastModified

interface.Ifso,thevalueofthe

longgetLastModified(request)

methodofthe

LastModified

interfaceisreturnedtotheclient.Youcancustomizeindividual

DispatcherServlet

instancesbyaddingServletinitializationparameters(init-param

elements)totheServletdeclarationinthe

web.xml

file.Thefollowingtableliststhesupportedparameters:Table1.DispatcherServletinitializationparametersParameterExplanationcontextClassClassthatimplements

ConfigurableWebApplicationContext,tobeinstantiatedandlocallyconfiguredbythisServlet.Bydefault,

XmlWebApplicationContext

isused.contextConfigLocationStringthatispassedtothecontextinstance(specifiedby

contextClass)toindicatewherecontextscanbefound.Thestringconsistspotentiallyofmultiplestrings(usingacommaasadelimiter)tosupportmultiplecontexts.Inthecaseofmultiplecontextlocationswithbeansthataredefinedtwice,thelatestlocationtakesspaceNamespaceofthe

WebApplicationContext.Defaultsto

[servlet-name]-servlet.throwExceptionIfNoHandlerFoundWhethertothrowa

NoHandlerFoundException

whennohandlerwasfoundforarequest.Theexceptioncanthenbecaughtwitha

HandlerExceptionResolver

(forexample,byusingan

@ExceptionHandler

controllermethod)andhandledasanyothers.Bydefault,thisissetto

false,inwhichcasethe

DispatcherServlet

setstheresponsestatusto404(NOT_FOUND)withoutraisinganexception.Notethat,if

defaultservlethandling

isalsoconfigured,unresolvedrequestsarealwaysforwardedtothedefaultservletanda404isneverraised.1.1.6.InterceptionAll

HandlerMapping

implementationssupporthandlerinterceptorsthatareusefulwhenyouwanttoapplyspecificfunctionalitytocertainrequests?—?forexample,checkingforaprincipal.Interceptorsmustimplement

HandlerInterceptor

fromtheorg.springframework.web.servlet

packagewiththreemethodsthatshouldprovideenoughflexibilitytodoallkindsofpre-processingandpost-processing:preHandle(..):BeforetheactualhandlerisexecutedpostHandle(..):AfterthehandlerisexecutedafterCompletion(..):AfterthecompleterequesthasfinishedThe

preHandle(..)

methodreturnsabooleanvalue.Youcanusethismethodtobreakorcontinuetheprocessingoftheexecutionchain.Whenthismethodreturns

true,thehandlerexecutionchaincontinues.Whenitreturnsfalse,the

DispatcherServlet

assumestheinterceptoritselfhastakencareofrequests(and,forexample,renderedanappropriateview)anddoesnotcontinueexecutingtheotherinterceptorsandtheactualhandlerintheexecutionchain.See

Interceptors

inthesectiononMVCconfigurationforexamplesofhowtoconfigureinterceptors.Youcanalsoregisterthemdirectlybyusingsettersonindividual

HandlerMapping

implementations.Notethat

postHandle

islessusefulwith

@ResponseBody

and

ResponseEntity

methodsforwhichtheresponseiswrittenandcommittedwithinthe

HandlerAdapter

andbefore

postHandle.Thatmeansitistoolatetomakeanychangestotheresponse,suchasaddinganextraheader.Forsuchscenarios,youcanimplement

ResponseBodyAdvice

andeitherdeclareitasan

ControllerAdvice

beanorconfigureitdirectlyon

RequestMappingHandlerAdapter.1.1.7.ExceptionsSameasinSpringWebFluxIfanexceptionoccursduringrequestmappingoristhrownfromarequesthandler(suchasa

@Controller),the

DispatcherServlet

delegatestoachainof

HandlerExceptionResolver

beanstoresolvetheexceptionandprovidealternativehandling,whichistypicallyanerrorresponse.Thefollowingtableliststheavailable

HandlerExceptionResolver

implementations:Table2.HandlerExceptionResolverimplementationsHandlerExceptionResolverDescriptionSimpleMappingExceptionResolverAmappingbetweenexceptionclassnamesanderrorviewnames.Usefulforrenderingerrorpagesinabrowserapplication.DefaultHandlerExceptionResolverResolvesexceptionsraisedbySpringMVCandmapsthemtoHTTPstatuscodes.Seealsoalternative

ResponseEntityExceptionHandler

and

RESTAPIexceptions.ResponseStatusExceptionResolverResolvesexceptionswiththe

@ResponseStatus

annotationandmapsthemtoHTTPstatuscodesbasedonthevalueintheannotation.ExceptionHandlerExceptionResolverResolvesexceptionsbyinvokingan

@ExceptionHandler

methodina

@Controllerora

@ControllerAdvice

class.See

@ExceptionHandlermethods.ChainofResolversYoucanformanexceptionresolverchainbydeclaringmultiple

HandlerExceptionResolver

beansinyourSpringconfigurationandsettingtheir

order

propertiesasneeded.Thehighertheorderproperty,thelatertheexceptionresolverispositioned.Thecontractof

HandlerExceptionResolver

specifiesthatitcanreturn:a

ModelAndView

thatpointstoanerrorview.Anempty

ModelAndView

iftheexceptionwashandledwithintheresolver.null

iftheexceptionremainsunresolved,forsubsequentresolverstotry,and,iftheexceptionremainsattheend,itisallowedtobubbleuptotheServletcontainer.The

MVCConfig

automaticallydeclaresbuilt-inresolversfordefaultSpringMVCexceptions,for

@ResponseStatus

annotatedexceptions,andforsupportof

@ExceptionHandler

methods.Youcancustomizethatlistorreplaceit.ContainerErrorPageIfanexceptionremainsunresolvedbyany

HandlerExceptionResolver

andis,therefore,lefttopropagateoriftheresponsestatusissettoanerrorstatus(thatis,4xx,5xx),ServletcontainerscanrenderadefaulterrorpageinHTML.Tocustomizethedefaulterrorpageofthecontainer,youcandeclareanerrorpagemappingin

web.xml.Thefollowingexampleshowshowtodoso:<error><location>/error</location></error>Giventheprecedingexample,whenanexceptionbubblesuportheresponsehasanerrorstatus,theServletcontainermakesanERRORdispatchwithinthecontainertotheconfiguredURL(forexample,

/error).Thisisthenprocessedbythe

DispatcherServlet,possiblymappingittoa

@Controller,whichcouldbeimplementedtoreturnanerrorviewnamewithamodelortorenderaJSONresponse,asthefollowingexampleshows:@RestControllerpublicclassErrorController{@RequestMapping(path="/error")publicMap<String,Object>handle(HttpServletRequestrequest){Map<String,Object>map=newHashMap<String,Object>();map.put("status",request.getAttribute("javax.servlet.error.status_code"));map.put("reason",request.getAttribute("javax.servlet.error.mes