外文翻译 - 基于MVC模式的图书馆信息管理系统的设计与实现

0外文原文TheDesignandRealizationofLibraryMISBasedonMVCKeywords:MVCmodel;JSP;Servlets;JavabeansAbstract.MVCisatypicalsoftwarearchitecturemodelThepaperstatesthedevelopmentprincipleandadvantagesoftheMVCpattern,discussesthesoftwaredevelopmentprocessbasedontheMVCpattern,anddesignsaWebapplicationlibrarymanagementsystem.Onthebasisofintroducingbooksmanagementsystem,thispaperdescribesthesystemdesignandimplementationmethodbasedonMVCpattern.TheuseofMVCmodelimprovesmaintainabilityandreusabilityofthesystem.INTRODUCTIONWiththerapidincreaseofthenetworkapplications,MVCparadigmisaveryadvanceddesignideaforWebapplicationdevelopment.Nomatterwhichlanguageyouchoose,nomatterhowcomplextheapplicationsare,itcanprovidethemostbasicanalysismethodfortheapplicationmodelstructural,provideacleardesigningforproducts,andprovidecanonicalreferenceforsoftwareengineering.ThisarticleraisesmanagementsystembasedonMVCparadigmonthebasisofresearchonlibrarymanagementsystem.MVCseparatestheinput,processing,andoutputofanapplicationaccordingtotheModel,ViewandController,thatis,three-tierdesignmode(namelymodellayer,viewlayerandcontrollayer).Itisnowwidelyusedinsoftwarearchitecturemodel.ThepaperusestheJSP+JavaBeans+Servlet+JDBCtechnologiestorealizetheMVCarchitecture.DisplayingWebpagesisusingJSP;realizingbusinessmodelsisusingJavaBeans,ControllingthedatatransmissionandfunctioncallbetweenforegroundandbackgroundisusingServlet;AccessingdatabaseisusingJDBC;storingdataisusingthedatabase.MVCDESIGNMODELMVCwasfirstdescribedin1979byTrygveReenskaug,thenworkingonSmalltalkatXeroxPARC.ModelViewController(MVC)isasoftwarearchitecture,currentlyconsideredanarchitecturalpatternusedinsoftwareengineering.Thepatternisolatesdomainlogic(theapplicationlogicfortheuser)fromtheuserinterface(inputandpresentation),1permittingindependentdevelopment,testingandmaintenanceofeach(separationofconcerns).A.thebasicstructureofMVCInarealapplication,thethreecomponentsofMVCareindependentandinterrelated.ThestructureandfunctionsofMVCmodelareasshowninFig.1.Themodelmanagesthebehavioranddataoftheapplicationdomain,respondstorequestsforinformationaboutitsstate(usuallyfromtheview),andrespondstoinstructionstochangestate(usuallyfromthecontroller).Inevent-drivensystems,themodelnotifiesobservers(usuallyviews)whentheinformationchangessothattheycanreact.DesignofbusinessmodelcanbesaidtobethemaincoreofMVC.Oneoftheimportantmodelsofbusinessmodelisthedatamodel.Datamodelisthedatasavingoftheentityobjects.Forexample,anorderissavedtothedatabaseorisobtainedfromthedatabase.Wecanlistthismodelseparately,alloperationsrelatedtothedatabasesarelimitedtothemodel.Theviewrepresentstheuserinterface.ItcanbedescribedasHTML,XHTML,XMLandAppletinterfacefortheWebapplication.Theviewrendersthemodelintoaformsuitableforinteraction,typicallyauserinterfaceelement.Multipleviewscanexistforasinglemodelfordifferentpurposes.Aviewporttypicallyhasaonetoonecorrespondencewithadisplaysurfaceandknowshowtorendertoit.Thecontrolleracceptstheuserrequest,matchmodelwithviewtofinishtheusersrequest.Thefunctionofdividingthecontrollayerisclear,itisadispatcherforchoosingwhatkindofmodels,choosingwhatkindofviewsandfinishingwhatkindofuserrequests.Thecontrollerreceivesinputandinitiatesaresponsebymakingcallsonmodelobjects.Acontrolleracceptsinputfromtheuserandinstructsthemodelandviewporttoperformactionsbasedonthatinput.Thecontrollercannotdoanydataprocessing.Forexample,usersclickonalink,thecontrolleracceptsrequest,anditdoesnothandlethebusinessinformation.Itpassestheusersinformationtothemodel,tellsthemodelwhattodo,choosestheviewthatmeetstherequirementstoreturntotheuser.Therefore,amodelmaycorrespondtomoreviews,andaviewmaycorrespondtomoremodels2B.thecontrolflowofMVCThoughMVCcomesindifferentflavors,controlflowisgenerallyasfollows:(1)Theuserinteractswiththeuserinterfaceinsomeway(usuallytheview,butnotnecessarily),forexample,pressesamousebutton.(2)Thecontrollerhandlestheinputeventfromtheuserinterface,oftenviaaregisteredhandlerorcallbackandconvertstheeventintoappropriateuseraction,understandableforthemodel.(3)Thecontrollernotifiesthemodeloftheuseraction,possiblyresultinginachangeinthemodelsstate.(Forexample,thecontrollerupdatestheusersshoppingcart.)(4)Aviewqueriesthemodelinordertogenerateanappropriateuserinterface(forexample,theviewliststheshoppingcartscontents).(5)Theviewgetsitsowndatafromthemodel.Insomeimplementations,thecontrollermayissueageneralinstructiontotheviewtorenderitself.Inothers,theviewisautomaticallynotifiedbythemodelofchangesinstate(Observer)whichrequireascreenupdate.Theuserinterfacewaitsforfurtheruserinteractions,whichrestartsthecycle.C.theadvantagesofMVC(1)Benefittodivisiondeployment.TodevelopapplicationusingMVCdesignpattern,personneldivisionofthedifferentfunctionsisveryclear.TousetheexampleofthedevelopmentofWebapplicationinJAVAlanguage,Javaprogrammersfocusonbusinesslogic,andinterfaceprogrammer(HTMLandJSPdevelopers)willjustconcentrateonthepageperformanceforms.(2)Increasethereuseoftheapplication.ForthesameWebapplication,theclientsmayusemultiplewaystoaccess.TheycanaccessnotonlybyHTMLbrowserofthecomputer,butalsobyWAPbrowserofthemobiletelephone.Butnomatterbywhatkindofaccessmode,thebusinesslogicandbusinessprocessoftheapplicationisthesame,youneedtochangetheconcreteimplementationwayofthepresentationlayer.MVCcansolvethisproblemeasilybecauseitrealizedtheseparationofthebusinessandview.(3)Reducecouplingandimprovethemaintainability.MVCdesignpatternseparatethe3presentationlayerandbusinesslayereffectively,itreducesthecouplingclosedegreebetweenthem.Therefore,anyalterationofthebusinesslogiccannotaffectthecodeofthepresentationlayer;thedeveloperscanmodifythecodeofthepresentationlayerfreely,andneednotrebuildthecodeofthemodelandthecontroller.D.thedisadvantagesofMVC(1)MVCisnotsuitableforthedevelopmentanddesignofsmallapplication.MVCdevelopingpersonneldividetheapplicationfullybasedonthemodel,viewandcontrol.Thiscanincreasesomeunnecessaryworkstoafewsmallapplications;thisaffectstheexploitationefficiency.(2)ProgrammingbasedonMVCdesignpatterndemandsthedevelopersmustwelldesigntheprogramstructurebeforetheprogramming;becausedividingawholeapplicationintothreecomponentsinthedesigningprocess,thisincreasesthenumberofthefileneedtomanage.SERVELETServletsaretheJavaplatformtechnologyofchoiceforextendingandenhancingWebservers.Servletsprovideacomponent-based,platform-independentmethodforbuildingWeb-basedapplications,withouttheperformancelimitationsofCGIprograms.Andunlikeproprietaryserverextensionmechanisms(suchastheNetscapeServerAPIorApachemodules),servletsareserverandplatform-independent.Thisleavesyoufreetoselectabestofbreedstrategyforyourservers,platforms,andtools.ServletshaveaccesstotheentirefamilyofJavaAPIs,includingtheJDBCAPItoaccessenterprisedatabases.ServletscanalsoaccessalibraryofHTTP-specificcallsandreceiveallthebenefitsofthematureJavalanguage,includingportability,performance,reusability,andcrashprotection.TodayservletsareapopularchoiceforbuildinginteractiveWebapplications.Third-partyservletcontainersareavailableforApacheWebServer,MicrosoftIIS,andothers.ServletcontainersareusuallyacomponentofWebandapplicationservers,suchasBEAWebLogicApplicationServer,IBMWebSphere,SunJavaSystemWebServer,SunJavaSystemApplicationServer,andothers.4TheServletisaJavaclass,anditcommunicatesandinteractswiththemodelbutdoesnotneedtogenerateHTMLorXHTMLoutput;theJSPsdonothavetocommunicatewiththemodelbecausetheServletprovidesthemwiththeinformationtheycanconcentrateoncreatingoutput.Theservletlifecycleconsistsofthefollowingsteps:(1)TheservletclassisloadedbytheWebcontainerduringstart-up.(2)Thecontainercallstheno-argumentconstructor.(3)TheWebcontainercallstheinit()method.Thismethodinitializestheservletandmustbecalledbeforetheservletcanserviceanyrequests.Intheentirelifeofaservlet,theinit()methodiscalledonlyonce.(4)Afterinitialization,theservletcanserviceclientrequests.Eachrequestisservicedinitsownseparatethread.TheWebcontainercallstheservice()methodoftheservletforeveryrequest.Theservice()methoddeterminesthekindofrequestbeingmadeanddispatchesittoanappropriatemethodtohandletherequest.Thedeveloperoftheservletmustprovideanimplementationforthesemethods.Ifarequestforamethodthatisnotimplementedbytheservletismade,themethodoftheparentclassiscalled,typicallyresultinginanerrorbeingreturnedtotherequester.(5)Finally,theWebcontainercallsthedestroy()methodthattakestheservletoutofservice.Thedestroy()method,likeinit(),iscalledonlyonceinthelifecycleofaservlet.DESIGNANDREALIZATIONOFLIBRARYMANAGEMENTSYSTEMBASEDONMVCA.OrganiccombinationofJSPServletsJavaBeansJSP+Servlets+JavaBeansisapplicationexampleofMVCpatterninJSPdevelopment,OrganicCombinationofthreecanimplementsystemfunctionwellofMVCmodel.LibrarymanagementsystemisbasedonMVCpattern;thewholemanagementsystemusesthreetierarchitectureofBrowser/Web/Database.TheclientssendrequeststoWebserverthroughbrowser,theservletrunninginserveraccepttherequests.Theservletinthesystemcanbeusedasthecontrolleroftheapplication,JSPpageisusedasviewandJavaBeanisusedasmodel.Servletreceivesallrequestssentbytheclients;itwillcallthedifferentJSPpagebasedontheacceptedrequests.Inordertofacilitatetheoperation,5sometimesServletmakesaJavaBeaninstanceusedbyJSPpagebasedonJSPpagesneeds.JSPpagecallsdirectlymethodorusestheuser-definedlabelstoobtainthedataofJavaBeaninstance.Thismethodallowstheoperationresultsreturningtotheusersintimewhenusersborrowandreturnthebooks;thismeetsthesystemreal-timerequirements.Inthisdesignmodel,datatransmissionofeverylayerisasshowninFig.2.Inthissystem,themodelisacollectionofJavaclassesthatformasoftwareapplicationintendedtostore,andoptionallyseparate,data.Asinglefront-endclassthatcancommunicatewithanyuserinterface(forexample:aconsole,agraphicaluserinterface,orawebapplication).TheviewisrepresentedbyaJavaServerPage,withdatabeingtransportedtothepageintheHttpServletRequestorHttpSession.TheControllerservletcommunicateswiththefrontendofthemodelandloadstheHttpServletRequestorHttpSessionwithappropriatedata,beforeforwardingtheHttpServletRequestandResponsetotheJSPusingaRequestDispatcher.B.designandrealizationoflibrarymanagementsystemThefunctionalrequirementsblockdiagramofthelibrarymanagementsystemisasshowninFig.3;theinformationquerymoduleisasshowninFig4.Theusecaseistheinteractionbetweenthesystemandtheusers;itpaysattentiontotheexternalusers.Theuserscanunderstandthesystemfunctionsbyusecase.Inthissystem,theusecaseisasshowninFig.5.Thecodesofthedatabaseconnectionisasfollows:/creatingthedatabaseconnectionpublicConnectiongetConnection()throwsExceptionClass.forName(com.microsoft.jdbc.sqlserver.SQLServerDriver);con=DriverManager.getConnection(jdbc:microsoft:sqlserver:/localhost:1433;DatabaseName=MyLibrary,sa,123);returncon;6Figure1.ThestructureandfunctionsofMVCmodelFigure2.DatatransmissioninMVC7Figure3.TheblockdiagramofthelibrarymanagementsystemFigure4.TheinformationquerymoduleCONCLUSIONSMVCdesignpatternmeetstheinterfacedemand;separatethecalculatingmodelofthe8softwarefromtheinterfaceconstitute.Itcanbuildandusemulti-viewswhenthemodelisrunning.Themodelhasportability,andisapotentialframestructure.Thelibrarymanagementsystemrealizedthemodulesofuserlogin,basicbusiness,DBmanagementandinformationquery,implementedpaperlessfiling,savedthecost.TheuseofMVCpatternreducesthecomplexityinarchitecturaldesignandincreasesflexibilityandmaintainabilityofcode,enhancedthedevelopmentefficiencyofthesystem.Figure5.Theusecaseoflibrarymanagementsystem9中文翻译基于MVC模式的图书馆信息管理系统的设计与实现关键词：MVC模式;JSP;Servlet;JavaBean摘要:MVC是一个典型的软件体系结构模型，阐述了MVC模式开发的原理和优势，论述了基于MVC模式的软件开发过程，并设计了一个Web应用的图书馆管理系统。在介绍了图书管理系统的基础上，本文介绍了基于MVC模式的方法的系统的设计与实现。MVC模式的使用提高了系统的可维护性和可重用性。引言随着网络应用的快速增加，MVC模式是Web应用开发的一个非常先进的设计理念。无论你选择哪种语言，无论多么复杂的应用程序，它可以为应用程序提供的模型结构最基本的分析方法，为产品提供一个明确的设计，并提供软件工程规范的参考。本文提出了基于MVC模式对图书馆管理系统研究的基础上管理系统。MVC设计模式分离的输入，处理，输出一个应用程序根据模型，视图和控制器，即，三层设计模式（即模型层，视图层和控制层）。它是目前广泛使用的软件体系结构模型。本文采用JSP+JavaBeans+SERVLET+JDBC技术来实现MVC架构。显示Web页面使用JSP实现业务模型；利用JavaBeans，控制和数据传输功能的前景和背景之间的呼叫使用Servlet；数据库的访问使用JDBC；存储数据用的是数据库。MVC设计模式MVC最初是在1979由TrygveReenskaug，然后在Smalltalk在施乐帕洛阿尔托研究中心。模型视图控制器（MVC）是软件体系结构，目前被认为是软件工程中使用的建筑模式。模式分离”域逻辑”（为用户应用程序逻辑）从用户接口（输入和演示），允许独立发展，每个测试和维护（关注点分离）。A.MVC的基本结构在实际的应用中，MVC的三个组成部分是独立的和相互关联的。MVC模型的结构和功能，如图1所示。模型管理的应用程序域的行为和数据，根据其状态信息请求（通常是从视图），和响应指令来改变状态（通常由控制器）。在事件驱动的系统模型，观察者（通常是通知视图）时，信息的变化，使他们能够作出反应。业务模型的设计可以说是MVC核心。一个商业模式的重要模型是数据模型。数据模型是数据存储的实体对象。例如，为了保存到数据库或从数据库中获得的。我们可以列出这个模型，所有的数据库操作仅限于模型。视图表示用户界面。它可以被描述为HTML，XHTML，XML为Web应用程序接口。视图渲染模型成适合于互动的形式，通常是一个用户界面元素。多个视图可以用10于不同目的的单一模式的存在。一个视口，通常有一一对应一个显示面和知道如何使它。控制器接受用户的请求，以完成用户的请求匹配模型。划分控制层的作用是明确的，它是一个选择什么样的模型调度，选择什么样的观点和完成什么样的用户请求。控制器接收输入的模型对象进行调用，发起一个响应。控制器接收来自用户输入和指导模型和视图的基础上执行输入操作。控制器不能做任何的数据处理。例如，用户点击一个链接，控制器接受请求，它不处理商业信息。它通过用户的信息模型，对模型做什么，选择符合要求返回到用户视图。因此，一个模型可能对应多个视图，以及视图可以对应于多个模型B.MVC的控制流虽然MVC有不同的口味，控制流程一般如下：（1）用户以某种方式与用户交互界面（通常的观点，但不一定），例如，按下鼠标按钮。（2）控制器处理输入事件从用户界面，往往通过注册处理程序或回调将事件到适当的用户行为，可以理解为模型。（3）控制器通知用户行为模型，可能会导致在模型中的状态的变化。（例如，控制器更新用户的购物车。）（4）一个视图的查询模型，以产生适当的用户界面（例如，视图列出购物车的内容）。（5）从模型中获取自己的数据。在一些实施例中，控制器可以发出指令给视图渲染自己。在其他情况下，视图自动通知状态变化的模型（观察者）需要一个屏幕更新。用户界面有待进一步的用户交互，并重新启动循环。C.MVC的优势（1）有利于分工部署。开发使用MVC设计模式的应用，不同功能的人员分工非常明确。利用Java语言的Web应用程序开发的实例，Java程序员专注于业务逻辑和界面，程序员（HTML和JSP开发人员）将专注于页面表现形式。（2）提高了应用程序的复用。对同一个Web应用程序，客户可以使用多种方式来访问。他们可以访问不仅通过HTML浏览器的计算机，而且通过WAP浏览器的移动电话。但没有哪种接入方式问题，应用程序的业务逻辑和业务过程是相同的，你需要改变表示层的具体实现方式。MVC可以解决这个问题很容易因为它实现了业务的分离和视图。（3）降低耦合度，提高系统的可维护性。MVC设计模式分离了表示层和业务层有效，它降低了它们之间的耦合度。因此，任何改变的业务逻辑不能影响表示层代码；开发商可以自由修改表现层的代码，而不需要重建代码的模型和控制器。11D.MVC的缺点（1）MVC是不适合与小应用程序的设计开发。MVC开发人员将完全基于模型的应用，查看和控制。这可以增加一些不必要的工作，一些小的应用程序的开发效率；影响。（2）基于MVC设计模式的编程要求开发商必须在规划设计的程序结构；由于将整个应用程序分为三个部分，在设计的过程中，这增加了文件的数量需要管理。ServletServlets是扩大和加强Web服务器选择Java平台技术。Servlet提供组件，构建基于Web的应用程序独立于平台的方法，没有CGI程序的性能限制。不像专有服务器扩展机制（如Netscape服务器API或Apache模块），Servlets服务器平台无关。这给你自由去选择一个“最佳”的策略，你的服务器，平台，和工具。Servlet访问JavaAPI的整个家庭，包括JDBCAPI访问企业数据库。servlet也可以访问特定的HTTP调用库和收到的所有好处的成熟的Java语言，包括便携性，性能，可重用性，和碰撞保护。今天的servlet是构建交互式Web应用程序的一个受欢迎的选择。第三方的servlet容器提供微软IIS，ApacheWeb服务器，和其他人。servlet容器通常是Web服务器和应用服务器组件，如BEAWebLogic应用服务器，IBMWebSphere，SunJava系统的Web服务器，SunJava应用服务器，和其他人。Servlet是一个Java类，它沟通和交互模型而不需要生成