毕业论文外文文献及翻译Word下载.docx
- 文档编号:18652686
- 上传时间:2022-12-31
- 格式:DOCX
- 页数:16
- 大小:35.24KB
毕业论文外文文献及翻译Word下载.docx
《毕业论文外文文献及翻译Word下载.docx》由会员分享,可在线阅读,更多相关《毕业论文外文文献及翻译Word下载.docx(16页珍藏版)》请在冰豆网上搜索。
名:
院:
业:
10210A021021010633
梁卓越
软件学院
软件工程(软件开发与测试)
指导教师:
韩涛常旭青
2014年6月
英文文献
出自《IBMSystemJournal,2006,44
(2):
33-37》作者:
MalcolmDavis
Struts——AnOpen-sourceMVCImplementation
ThisarticleintroducesStruts,aModel-View-ControllerimplementationthatusesservletsandJavaServerPages(JSP)technology.StrutscanhelpyoucontrolchangeinyourWebprojectandpromotespecialization.EvenifyouneverimplementasystemwithStruts,youmaygetsomeideasforyourfutureservletsandJSPpageimplementation
Introduction
KidsingradeschoolputHTMLpagesontheInternet.However,thereisamonumentaldifferencebetweenagradeschoolpageandaprofessionallydevelopedWebsite.Thepagedesigner(orHTMLdeveloper)mustunderstandcolors,thecustomer,productflow,pagelayout,browsercompatibility,imagecreation,JavaScript,andmore.Puttingagreatlookingsitetogethertakesalotofwork,andmostJavadevelopersaremoreinterestedincreatingagreatlookingobjectinterfacethanauserinterface.JavaServerPages(JSP)technologyprovidesthegluebetweenthepagedesignerandtheJavadeveloper.
Ifyouhaveworkedonalarge-scaleWebapplication,youunderstandthetermchange.Model-View-Controller(MVC)isadesignpatternputtogethertohelpcontrolchange.MVCdecouplesinterfacefrombusinesslogicanddata.StrutsisanMVCimplementationthatusesServlets2.2andJSP1.1tags,fromtheJ2EEspecifications,aspartoftheimplementation.YoumayneverimplementasystemwithStruts,butlookingatStrutsmaygiveyousomeideasonyourfutureServletsandJSPimplementations.
Model-View-Controller(MVC)
JSPtagssolvedonlypartofourproblem.Westillhaveissueswithvalidation,flowcontrol,andupdatingthestateoftheapplication.ThisiswhereMVCcomestotherescue.MVChelpsresolvesomeoftheissueswiththesinglemoduleapproachbydividingtheproblemintothreecategories:
Model
Themodelcontainsthecoreoftheapplication'
sfunctionality.Themodelencapsulatesthestateoftheapplication.Sometimestheonlyfunctionalityitcontainsisstate.Itknowsnothingaboutthevieworcontroller.
View
Theviewprovidesthepresentationofthemodel.Itisthelookoftheapplication.Theviewcanaccessthemodelgetters,butithasnoknowledgeofthesetters.Inaddition,itknowsnothingaboutthecontroller.Theviewshouldbenotifiedwhenchangestothemodeloccur.
Controller
Thecontrollerreactstotheuserinput.Itcreatesandsetsthemodel.
MVCModel2
TheWebbroughtsomeuniquechallengestosoftwaredevelopers,mostnotablythestatelessconnectionbetweentheclientandtheserver.Thisstatelessbehaviormadeitdifficultforthemodeltonotifytheviewofchanges.OntheWeb,thebrowserhastore-querytheservertodiscovermodificationtothestateoftheapplication.
Anothernoticeablechangeisthattheviewusesdifferenttechnologyforimplementationthanthemodelorcontroller.Ofcourse,wecoulduseJava(orPERL,C/C++orwhatever)codetogenerateHTML.Thereareseveraldisadvantagestothatapproach:
Javaprogrammersshoulddevelopservices,notHTML.
Changestolayoutwouldrequirechangestocode.
Customersoftheserviceshouldbeabletocreatepagestomeettheirspecificneeds.
Thepagedesignerisn'
tabletohavedirectinvolvementinpagedevelopment.HTMLembeddedintocodeisugly.
FortheWeb,theclassicalformofMVCneededtochange.Figure4displaystheWebadaptationofMVC,alsocommonlyknownasMVCModel2orMVC2.
Strutsdetails
DisplayedinFigure6isastripped-downUMLdiagramoftheorg.apache.struts.actionpackage.Figure6showstheminimalrelationshipsamongActionServlet(Controller),ActionForm(FormState),andAction(ModelWrapper).
TheActionServletclass
Doyourememberthedaysoffunctionmappings?
Youwouldmapsomeinputeventtoapointertoafunction.Ifyouwhereslick,youwouldplacetheconfigurationinformationintoafileandloadthefileatruntime.FunctionpointerarrayswerethegoodolddaysofstructuredprogramminginC.
LifeisbetternowthatwehaveJavatechnology,XML,J2EE,andallthat.TheStrutsControllerisaservletthatmapsevents(aneventgenerallybeinganHTTPpost)toclasses.Andguesswhat--theControllerusesaconfigurationfilesoyoudon_thavetohard-codethevalues.Lifechanges,butstaysthesame.
ActionServletistheCommandpartoftheMVCimplementationandisthecoreoftheFramework.ActionServlet(Command)createsandusesAction,anActionForm,andActionForward.Asmentionedearlier,thestruts-config.xmlfileconfigurestheCommand.DuringthecreationoftheWebproject,ActionandActionFormareextendedtosolvethespecificproblemspace.Thefilestruts-config.xmlinstructsActionServletonhowtousetheextendedclasses.Thereareseveraladvantagestothisapproach:
Theentirelogicalflowoftheapplicationisinahierarchicaltextfile.Thismakesiteasiertoviewandunderstand,especiallywithlargeapplications.ThepagedesignerdoesnothavetowadethroughJavacodetounderstandtheflowoftheapplication.
TheJavadeveloperdoesnotneedtorecompilecodewhenmakingflowchanges.
CommandfunctionalitycanbeaddedbyextendingActionServlet.
TheActionFormclass
ActionFormmaintainsthesessionstatefortheWebapplication.ActionFormisanabstractclassthatissub-classedforeachinputformmodel.WhenIsayinputformmodel,IamsayingActionFormrepresentsageneralconceptofdatathatissetorupdatedbyaHTMLform.Forinstance,youmayhaveaUserActionFormthatissetbyanHTMLForm.TheStrutsframeworkwill:
ChecktoseeifaUserActionFormexists;
ifnot,itwillcreateaninstanceoftheclass.
StrutswillsetthestateoftheUserActionFormusingcorrespondingfieldsfromtheHttpServletRequest.Nomoredreadfulrequest.getParameter()calls.Forinstance,theStrutsframeworkwilltakefnamefromrequeststreamandcallUserActionForm.setFname().
TheStrutsframeworkupdatesthestateoftheUserActionFormbeforepassingittothebusinesswrapperUserAction.
BeforepassingittotheActionclass,Strutswillalsoconductformstatevalidationbycallingthevalidation()methodonUserActionForm.Note:
Thisisnotalwayswisetodo.TheremightbewaysofusingUserActionForminotherpagesorbusinessobjects,wherethevalidationmightbedifferent.ValidationofthestatemightbebetterintheUserActionclass.
TheUserActionFormcanbemaintainedatasessionlevel.
Notes:
Thestruts-config.xmlfilecontrolswhichHTMLformrequestmapstowhichActionForm.
MultiplerequestscanbemappedUserActionForm.
UserActionFormcanbemappedovermultiplepagesforthingssuchaswizards.
TheActionclass
TheActionclassisawrapperaroundthebusinesslogic.ThepurposeofActionclassistotranslatetheHttpServletRequesttothebusinesslogic.TouseAction,subclassandoverwritetheprocess()method.
TheActionServlet(Command)passestheparameterizedclassestoActionFormusingtheperform()method.Again,nomoredreadfulrequest.getParameter()calls.Bythe
timetheeventgetshere,theinputformdata(orHTMLformdata)hasalreadybeentranslatedoutoftherequeststreamandintoanActionFormclass.
Struts,anMVC2implementation
Strutsisasetofcooperatingclasses,servlets,andJSPtagsthatmakeupareusableMVC2design.ThisdefinitionimpliesthatStrutsisaframework,ratherthanalibrary,butStrutsalsocontainsanextensivetaglibraryandutilityclassesthatworkindependentlyoftheframework.Figure5displaysanoverviewofStruts.
Strutsoverview
Clientbrowser
AnHTTPrequestfromtheclientbrowsercreatesanevent.TheWebcontainerwillrespondwithanHTTPresponse.
TheControllerreceivestherequestfromthebrowser,andmakesthedecisionwheretosendtherequest.WithStruts,theControllerisacommanddesignpatternimplementedasaservlet.Thestruts-config.xmlfileconfigurestheController.
Businesslogic
Thebusinesslogicupdatesthestateofthemodelandhelpscontroltheflowoftheapplication.WithStrutsthisisdonewithanActionclassasathinwrappertotheactualbusinesslogic.
Modelstate
Themodelrepresentsthestateoftheapplication.Thebusinessobjectsupdatetheapplicationstate.ActionFormbeanrepresentstheModelstateatasessionorrequestlevel,andnotatapersistentlevel.TheJSPfilereadsinformationfromtheActionFormbeanusingJSPtags.
TheviewissimplyaJSPfile.Thereisnoflowlogic,nobusinesslogic,andnomodelinformation--justtags.TagsareoneofthethingsthatmakeStrutsuniquecomparedtootherframeworkslikeVelocity.
Note:
"
Thinkthin"
whenextendingtheActionclass.TheActionclassshouldcontroltheflowandnotthelogicoftheapplication.ByplacingthebusinesslogicinaseparatepackageorEJB,weallowflexibilityandreuse.
AnotherwayofthinkingaboutActionclassisastheAdapterdesignpattern.ThepurposeoftheActionisto"
Converttheinterfaceofaclassintoanotherinterfacetheclientsexpect.Adapterletsclassesworktogetherthatcouldn_totherwisebecauseofincompatibilityinterface"
(fromDesignPatterns-ElementsofReusableOOSoftwarebyGof).TheclientinthisinstanceistheActionServletthatknowsnothingaboutourspecificbusinessclassinterface.Therefore,Strutsprovidesabusinessinterfaceitdoesunderstand,Action.ByextendingtheAction,wemakeourbusinessinterfacecompatiblewithStrutsbusinessinterface.(AninterestingobservationisthatActionis
aclassandnotaninterface.
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 毕业论文 外文 文献 翻译