毕业设计外文文献—Spring Boot的Web应用程序.docx

毕业设计外文文献—Spring Boot的Web应用程序.docx

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附录A外文翻译—原文部分

F.Gutierrez，ProSpringBoot2

WebApplicationswithSpringBoot

Nowadays,thewebisthemainchannelforanytypeofapplication—fromdesktoptomobiledevices,fromsocialandbusinessapplicationstogames,andfromsimplecontenttostreamingdata.Withthisismind,SpringBootcanhelpyoueasilydevelopthenextgenerationofwebapplications.

ThischaptershowsyouhowtocreateSpringBootwebapplicationswithease.Youhavealreadylearned,withsomeexamplesinearlierchapters,whatyoucandowiththeweb.YoulearnedthatSpringBootmakesiteasiertocreatewebappswithafewlinesofcodeandthatyoudon’tneedtoworryaboutconfigurationfilesorlookforanapplicationservertodeployyourwebapplication.ByusingSpringBootanditsauto-configuration,youcanhaveanembeddedapplicationserver,suchasTomcat,Nettie,Undertow,orJetty,whichmakesyourappverydistributableandportable.

SpringMVC

Let’sstarttalkingabouttheSpringMVCtechnologyandsomeofitsfeatures.RememberthattheSpringFrameworkconsistsofabout20modulesortechnologies,andthewebtechnologyisoneofthem.Forthewebtechnology,theSpringFrameworkhasthespring-web,spring-webmvc,spring-webflux,andspring-websocketmodules.

Thespring-webmodulehasbasicwebintegrationfeatures,suchasmultipartfileuploadfunctionality,initializationoftheSpringcontainer（byusingservletlisteners）,andaweb-orientedapplicationcontext.Thespring-mvcmodule（a.k.a.,thewebservermodule）containsalltheSpringMVC（Model-View-Controller）andRESTservicesimplementationsforwebapplications.Thesemodulesprovidemanyfeatures,suchasverypowerfulJSPtaglibraries,customizablebindingandvalidation,flexiblemodeltransfer,customizablehandlerandviewresolution,andsoon.

TheSpringMVCisdesignedaroundtheorg.springframework.web.servlet.DispatcherServletclass.Thisservletisveryflexibleandhasaveryrobustfunctionalitythatyouwon’tfindinanyotherMVCwebframeworkoutthere.WiththeDispatcherServlet,youhaveseveralout-of-the-boxresolutionsstrategies,includingviewresolvers,localeresolvers,themeresolvers,andexceptionhandlers.Inotherwords,theDispatcherServlettakeaHTTPrequestandredirectittotherighthandler（theclassmarkedwiththe@Controlleror@RestControllerandthemethodsthatusethe@RequestMappingannotations）andtherightview（yourJSPs）.

SpringBootMVCAuto-Configuration

Webapplicationscanbecreatedeasilybyaddingthespring-boot-starter-webdependencytoyourpom.xmlorbuildgradlefile.Thisdependencyprovidesallthenecessaryspring-webjarsandsomeextraones,suchastomcat-embed*andjackson（forJSONandXML）.ThismeansthatSpringBootusesthepoweroftheSpringMVCmodulesandprovidesallthenecessaryauto-configurationforcreatingtherightwebinfrastructure,suchasconfiguringtheDispatcherServlet,providingdefaults（unlessyouoverrideit）,settingupanembeddedTomcatserver（soyoucanrunyourapplicationwithoutanyapplicationcontainers）,andmore.

Auto-configurationaddsthefollowingfeaturestoyourwebapplication.

Staticcontentsupport.Thismeansthatyoucanaddstaticcontent,suchasHTML,JavaScript,CSS,media,andsoforth,inadirectorynamed/static（bydefault）or/public,/resources,or/META-INF/resources,whichshouldbeinyouclasspathorinyourcurrentdirectory.SpringBootpicksitupandservesthemuponrequest.Youcanchangethiseasilybymodifyingthespring.mvc.static-path-patternorthespring.resources.static-locationsproperties.OneofthecoolfeatureswithSpringBootandwebapplicationsisthatifyoucreateanindex.htmlfile,SpringBootservesitautomaticallywithoutregisteringanyotherbeanortheneedforextraconfiguration.

HttpMessageConverters.IfyouareusingaregularSpringMVCapplicationandyouwanttogetaJSONresponse,youneedtocreatethenecessaryconfiguration（XMLorJavaConfig）fortheHttpMessageConvertersbean.SpringBootaddsthissupportbydefaultsoyoudon’thaveto;thismeansthatyougettheJSONformatbydefault（duetotheJacksonlibrariesthatthespring-boot-starter-webprovidesasdependencies）.AndifSpringBootauto-configurationfindsthatyouhavetheJacksonXMLextensioninyouclasspath,itaggregatesanXMLHttpMessageConvertertotheconverters,meaningthatyourapplicationcanserverbasedonyourcontent-typerequest,eitherapplication/jsonorapplication/xml.

JSONserializersanddeserializers.Ifyouwanttohavemorecontrolovertheserialization/deserializationto/fromJSON,SpringBootprovidesaneasywaytocreateyourownbyextendingfromJsonSerializer<T>andJsonDeserializer<T>,andannotatingyourclasswiththe@JsonComponentsothatitcanberegisteredforusage.AnotherfeatureofSpringBootistheJacksonsupport;bydefault,SpringBootserializesthedatefieldsas2018-05-01T23:

31:

38.141+0000,butyoucanchangethisdefaultbehaviorbychangingthespring.jackson.date-format=yyyy-MM-ddproperty（youcanapplyanydateformatpattern）;thepreviousvaluegeneratestheoutput,suchas2018-05-01.

Pathmatchingandcontentnegotiation.OneoftheSpringMVCapplicationpracticesistheabilitytorespondtoanysuffixtorepresentthecontent-typeresponseanditscontentnegotiation.Ifyouhavesomethinglike/api/todo.jsonor/api/todo.pdf,thecontent-typeissettoapplication/jsonandapplication/pdf;sotheresponseisJSONformatoraPDFfile,respectively.Inotherwords,SpringMVCperforms.*suffixpatternmatching,suchas/api/todo.*.SpringBootdisablesthisbydefault.Youcanstilluseafeaturewhereyoucanaddaparameter,byusingthespring.mvc.contentnegotiation.favor-parameter=trueproperty（falsebydefault）;soyoucandosomethinglike/api/todoformat=xml.（formatisthedefaultparametername;ofcourse,youcanchangeitwithspring.mvc.contentnegotiation.parameter-name=myparam）.Thistriggersthecontent-typetoapplication/xml.

Errorhandling.SpringBootuses/errormappingtocreateawhitelabeledpagetoshowalltheglobalerrors.Youcanchangethebehaviorbycreatingyourowncustompages.YouneedtocreateyourcustomHTMLpageinthesrc/main/resources/public/error/location,soyoucancreate500.htmlor404.htmlpagesforexample.IfyouarecreatingaRESTfulapplication,SpringBootrespondsasJSONformat.SpringBootalsosupportsSpringMVCtohandleerrorswhenyouareusing@ControllerAdviceor@ExceptionHandlerannotations.YoucanregistercustomErrorPagesbyimplementingErrorPageRegistraranddeclaringitasaSpringbean.

Templateenginesupport.SpringBootsupportsFreeMarker,GroovyTemplates,Thymeleaf,andMustache.Whenyouincludethespring-boot-starter-<templateengine>dependency,SpringBootauto-configureisnecessarytoenableandaddallthenecessaryviewresolversandfilehandlers.Bydefault,SpringBootlooksatthesrc/main/resources/templates/path.

AndtherearemanyotherfeaturesthatSpringBootWebauto-configureprovides.Rightnow,weareonlylookingattheServlettechnology,butverysoonwegetintothenewestadditiontotheSpringBootfamily:

WebFlux.

SpringBootWeb:

ToDoApp

TobetterunderstandhowSpringBootworkswithwebapplicationsandthepoweroftheSpringMVCmodules,youaregoingtocreateaToDoappthatexposesaRESTfulAPI.Thesearetherequirements:

CreateaToDodomainmodelthathasthefollowingfieldsandtypes:

id（String）,description（String）,completed（Boolean）,created（datewithtime）,modified（datewithtime）.

CreateaRESTfulAPIthatprovidesthebasicCRUD（create,read,update,delete）actions.UsethemostcommonHTTPmethods:

POST,PUT,PATCH,GET,andDELETE.

CreatearepositorythathandlesthestateofmultipleToDo’s.Fornow,anin-memoryrepositoryisenough.

AddanerrorhandlerwhenthereisabadrequestorwhensubmittinganewToDodoesn’thavetherequiredfields.Theonlymandatoryfieldisthedescription.

AlltherequestsandresponsesshouldbeinJSONformat.

ToDoApp

Openyourbrowserandgotohttps:

//start.spring.iotocreateyourToDoappbyusingthefollowingvalues.

Group:

com.apress.todo

Artifact:

todo-in-memory

Name:

todo-in-memory

PackageName:

com.apress.todo

Dependencies:

Web,Lombok

ChoosingtheLombokdependencyhelpseasilycreatethedomainmodelclassesandeliminatestheboilerplatesetters,getters,andotheroverrides.

YoucanselecteitherMavenorGradleastheprojecttype;inthisbook,weusebothindistinctly.PresstheGenerateProjectbuttonanddownloadtheZIPfile.UncompressitandimportitintoyourfavoriteIDE.SomeofthebestIDEsareSTS（https:

//spring.io/tools/sts/all）,IntelliJIDEA（/idea/）,andVSCod（/）.IrecommendoneoftheseIDEsforthecodecompletionfeature,whichhelpsyouseethemethodsorparameterstoaddtoyourcode.

DomainModel:

ToDo

Basedontherequirements,youneedtocreateaToDodomainmodelclass.

showsyoutheToDoclass,whichhasalltherequiredfields.Italsousesthe@Dataannotation,whichisaLombokannotationthatgeneratesadefaultconstructor（ifyoudon’thaveone）andallthesetters,getters,andoverrides,suchasthetoStringmethod,tomaketheclasscleaner.Alsonotethattheclasshasthe@NotNulland@NotBlankannotationsinsomeofthefields;theseannotationsareusedinthevalidationthatwedolateron.Thedefaultconstructorhasfieldinitialization,soitiseasytocreateaToDoinstance.

FluentAPI:

ToDoBuilder

Nextlet’screateaFluentAPIclassthathelpscreateaToDoinstance.YoucanseethisclassafactorythatcreatesaToDowithadescriptionorwithaparticularID.

Repository:

CommonRepository<T>.Next,c