畢業(yè)設(shè)計(jì)管理系統(tǒng)的設(shè)計(jì)與實(shí)現(xiàn)開(kāi)題報(bào)告程序源代碼外文翻譯

北京信息科技大學(xué)畢業(yè)設(shè)計(jì)（論文）附錄題目：畢業(yè)設(shè)計(jì)管理系統(tǒng)的設(shè)計(jì)與實(shí)現(xiàn)學(xué)院：信息管理學(xué)院專(zhuān)業(yè)：信息管理與信息系統(tǒng)學(xué)生姓名：班級(jí)/學(xué)號(hào)指導(dǎo)老師/督導(dǎo)老師：起止時(shí)間：目錄目錄附件1：開(kāi)題報(bào)告……………共3頁(yè)附件2：程序源代碼………………………共64頁(yè)附件3：外文文獻(xiàn)譯文………………………共4頁(yè)附件4：外文文獻(xiàn)原文………………………共7頁(yè)

開(kāi)題報(bào)告附件4：外文文獻(xiàn)原文JSPapplicationframeworksWhatareapplicationframeworks:Aframeworkisareusable,semi-completeapplicationthatcanbespecializedtoproducecustomapplications[Johnson].Likepeople,softwareapplicationsaremorealikethantheyaredifferent.Theyrunonthesamecomputers,expectinputfromthesamedevices,outputtothesamedisplays,andsavedatatothesameharddisks.Developersworkingonconventionaldesktopapplicationsareaccustomedtotoolkitsanddevelopmentenvironmentsthatleveragethesamenessbetweenapplications.Applicationframeworksbuildonthiscommongroundtoprovidedeveloperswithareusablestructurethatcanserveasthefoundationfortheirownproducts.Aframeworkprovidesdeveloperswithasetofbackbonecomponentsthathavethefollowingcharacteristics:1.Theyareknowntoworkwellinotherapplications.2.Theyarereadytousewiththenextproject.3.Theycanalsobeusedbyotherteamsintheorganization.Frameworksaretheclassicbuild-versus-buyproposition.Ifyoubuildit,youwillunderstanditwhenyouaredone—buthowlongwillitbebeforeyoucanrollyourown?Ifyoubuyit,youwillhavetoclimbthelearningcurve—andhowlongisthatgoingtotake?Thereisnorightanswerhere,butmostobserverswouldagreethatframeworkssuchasStrutsprovideasignificantreturnoninvestmentcomparedtostartingfromscratch,especiallyforlargerprojects.Othertypesofframeworks:Theideaofaframeworkappliesnotonlytoapplicationsbuttoapplicationcomponentsaswell.Throughoutthisarticle,weintroduceothertypesofframeworksthatyoucanusewithStruts.TheseincludetheLucenesearchengine,theScaffoldtoolkit,theStrutsvalidator,andtheTilestaglibrary.Likeapplicationframeworks,thesetoolsprovidesemi-completeversionsofasubsystemthatcanbespecializedtoprovideacustomcomponent.Someframeworkshavebeenlinkedtoaproprietarydevelopmentenvironment.ThisisnotthecasewithStrutsoranyoftheotherframeworksshowninthisbook.YoucanuseanydevelopmentenvironmentwithStruts:VisualAgeforJava,JBuilder,Eclipse,Emacs,andTextpadareallpopularchoicesamongStrutsdevelopers.IfyoucanuseitwithJava,youcanuseitwithStruts.Enablingtechnologies:ApplicationsdevelopedwithStrutsarebasedonanumberofenablingtechnologies.ThesecomponentsarenotspecifictoStrutsandunderlieeveryJavawebapplication.AreasonthatdevelopersuseframeworkslikeStrutsistohidethenastydetailsbehindacronymslikeHTTP,CGI,andJSP.AsaStrutsdeveloper,youdon’tneedtobeanalphabetsoupguru,butaworkingknowledgeofthesebasetechnologiescanhelpyoudevisecreativesolutionstotrickyproblems.HypertextTransferProtocol(HTTP):Whenmediatingtalksbetweennations,diplomatsoftenfollowaformalprotocol.Diplomaticprotocolsaredesignedtoavoidmisunderstandingsandtokeepnegotiationsfrombreakingdown.Inasimilarvein,whencomputersneedtotalk,theyalsofollowaformalprotocol.Theprotocoldefineshowdataistransmittedandhowtodecodeitonceitarrives.WebapplicationsusetheHypertextTransferProtocol(HTTP)tomovedatabetweenthebrowserrunningonyourcomputerandtheapplicationrunningontheserver.ManyserverapplicationscommunicateusingprotocolsotherthanHTTP.Someofthesemaintainanongoingconnectionbetweenthecomputers.Theapplicationserverknowsexactlywhoisconnectedatalltimesandcantellwhenaconnectionisdropped.Becausetheyknowthestateofeachconnectionandtheidentityofeachpersonusingit,theseareknownasstatefulprotocols.Bycontrast,HTTPisknownasastatelessprotocol.AnHTTPserverwillacceptanyrequestfromanyclientandwillalwaysprovidesometypeofresponse,eveniftheresponseisjusttosayno.Withouttheoverheadofnegotiatingandretainingaconnection,statelessprotocolscanhandlealargevolumeofrequests.ThisisonereasonwhytheInternethasbeenabletoscaletomillionsofcomputers.AnotherreasonHTTPhasbecometheuniversalstandardisitssimplicity.AnHTTPrequestlookslikeanordinarytextdocument.ThishasmadeiteasyforapplicationstomakeHTTPrequests.YoucanevensendanHTTPrequestbyhandusingastandardutilitysuchasTelnet.WhentheHTTPresponsecomesback,itisalsoinplaintextthatdeveloperscanread.ThefirstlineintheHTTPrequestcontainsthemethod,followedbythelocationoftherequestedresourceandtheversionofHTTP.ZeroormoreHTTPrequestheadersfollowtheinitialline.TheHTTPheadersprovideadditionalinformationtotheserver.Thiscanincludethebrowsertypeandversion,acceptabledocumenttypes,andthebrowser’scookies,justtonameafew.Ofthesevenrequestmethods,GETandPOSTarebyfarthemostpopular.Oncetheserverhasreceivedandservicedtherequest,itwillissueanHTTPresponse.ThefirstlineintheresponseiscalledthestatuslineandcarriestheHTTPprotocolversion,anumericstatus,andabriefdescriptionofthestatus.Followingthestatusline,theserverwillreturnasetofHTTPresponseheadersthatworkinawaysimilartotherequestheaders.Aswementioned,HTTPdoesnotpreservestateinformationbetweenrequests.Theserverlogstherequest,sendstheresponse,andgoesblissfullyontothenextrequest.Whilesimpleandefficient,astatelessprotocolisproblematicfordynamicapplicationsthatneedtokeeptrackoftheirusers.(Ignoranceisnotalwaysbliss.CookiesandURLrewritingaretwocommonwaystokeeptrackofusersbetweenrequests.Acookieisaspecialpacketofinformationontheuser’scomputer.URLrewritingstoresaspecialreferenceinthepageaddressthataJavaservercanusetotrackusers.Neitherapproachisseamless,andusingeithermeansextraworkwhendevelopingawebapplication.Onitsown,astandardHTTPwebserverdoesnottrafficindynamiccontent.Itmainlyusestherequesttolocateafileandthenreturnsthatfileintheresponse.ThefileistypicallyformattedusingHypertextMarkupLanguage(HTML)[W3C,HTML]thatthewebbrowsercanformatanddisplay.TheHTMLpageoftenincludeshypertextlinkstootherwebpagesandmaydisplayanynumberofothergoodies,suchasimagesandvideos.Theuserclicksalinktomakeanotherrequest,andtheprocessbeginsanew.Standardwebservershandlestaticcontentandimagesquitewellbutneedahelpinghandtoprovideuserswithacustomized,dynamicresponse.DEFINITION:StaticcontentontheWebcomesdirectlyfromtextordatafiles,likeHTMLorJPEGfiles.Thesefilesmightbechangedfromtimetotime,buttheyarenotalteredautomaticallywhenrequestedbyawebbrowser.Dynamiccontent,ontheotherhand,isgeneratedonthefly,typicallyinresponsetoanindividualizedrequestfromabrowser.CommonGatewayInterface(CGI):ThefirstwidelyusedstandardforproducingdynamiccontentwastheCommonGatewayInterface(CGI).CGIusesstandardoperatingsystemfeatures,suchasenvironmentvariablesandstandardinputandoutput,tocreateabridge,orgateway,betweenthewebserverandotherapplicationsonthehostmachine.Theotherapplicationscanlookattherequestsenttothembythewebserverandcreateacustomizedresponse.Whenawebserverreceivesarequestthat’sintendedforaCGIprogram,itrunsthatprogramandprovidestheprogramwithinformationfromtheincomingrequest.TheCGIprogramrunsandsendsitsoutputbacktotheserver.Thewebserverthenrelaystheresponsetothebrowser.CGIdefinesasetofconventionsregardingwhatinformationitwillpassasenvironmentvariablesandhowitexpectsstandardinputandoutputtobeused.LikeHTTP,CGIisflexibleandeasytoimplement,andagreatnumberofCGI-awareprogramshavebeenwritten.ThemaindrawbacktoCGIisthatitmustrunanewcopyoftheCGI-awareprogramforeachrequest.Thisisarelativelyexpensiveprocessthatcanbogdownhigh-volumesiteswherethousandsofrequestsareservicedperminute.AnotherdrawbackisthatCGIprogramstendtobeplatformdependent.ACGIprogramwrittenforoneoperatingsystemmaynotrunonanother.Javaservlets:Sun’sJavaServletplatformdirectlyaddressesthetwomaindrawbacksofCGIprograms.First,servletsofferbetterperformanceandutilizationofresourcesthanconventionalCGIprograms.Second,thewrite-once,run-anywherenatureofJavameansthatservletsareportablebetweenoperatingsystemsthathaveaJavaVirtualMachine(JVM).Aservletlooksandfeelslikeaminiaturewebserver.Itreceivesarequestandrendersaresponse.But,unlikeconventionalwebservers,theservletapplicationprogramminginterface(API)isspecificallydesignedtohelpJavadeveloperscreatedynamicapplications.TheservletitselfissimplyaJavaclassthathasbeencompiledintobytecode,likeanyotherJavaobject.TheservlethasaccesstoarichAPIofHTTP-specificservices,butitisstilljustanotherJavaobjectrunninginanapplicationandcanleverageallyourotherJavaassets.Togiveconventionalwebserversaccesstoservlets,theservletsarepluggedintocontainers.Theservletcontainerisattachedtothewebserver.EachservletcandeclarewhatURLpatternsitwouldliketohandle.Whenarequestmatchingaregisteredpatternarrives,thewebserverpassestherequesttothecontainer,andthecontainerinvokestheservlet.ButunlikeCGIprograms,anewservletisnotcreatedforeachrequest.Oncethecontainerinstantiatestheservlet,itwilljustcreateanewthreadforeachrequest.JavathreadsaremuchlessexpensivethantheserverprocessesusedbyCGIprograms.Oncetheservlethasbeencreated,usingitforadditionalrequestsincursverylittleoverhead.Servletdeveloperscanusetheinit()methodtoholdreferencestoexpensiveresources,suchasdatabaseconnectionsorEJBHomeInterfaces,sothattheycanbesharedbetweenrequests.Acquiringresourceslikethesecantakeseveralseconds—whichislongerthanmanysurfersarewillingtowait.Theotheredgeoftheswordisthat,sinceservletsaremultithreaded,servletdevelopersmusttakespecialcaretobesuretheirservletsarethread-safe.Tolearnmoreaboutservletprogramming,werecommendJavaServletsbyExample,byAlanR.Williamson[Williamson].ThedefinitivesourceforServletinformationistheJavaServletSpecification[Sun,JST].JavaServerPages:WhileJavaservletsareabigstepupfromCGIprograms,theyarenotapanacea.Togeneratetheresponse,developersarestillstuckwithusingprintlnstatementstorendertheHTML.Codethatlookslike:out.println("<P>OnelineofHTML.</P>");out.println("<P>AnotherlineofHTML.</P>");isalltoocommoninservletsthatgeneratetheHTTPresponse.TherearelibrariesthatcanhelpyougenerateHTML,butasapplicationsgrowmorecomplex,JavadevelopersendupbeingcastintotheroleofHTMLpagedesigners.Meanwhile,giventhechoice,mostprojectmanagersprefertodividedevelopmentteamsintospecializedgroups.TheylikeHTMLdesignerstobeworkingonthepresentationwhileJavaengineerssweatthebusinesslogic.Usingservletsaloneencouragesmixingmarkupwithbusinesslogic,makingitdifficultforteammemberstospecialize.Tosolvethisproblem,Sunturnedtotheideaofusingserverpagestocombinescriptingandtemplatingtechnologiesintoasinglecomponent.TobuildJavaServerPages,developersstartbycreatingHTMLpagesinthesameoldway,usingthesameoldHTMLsyntax.Tobringdynamiccontentintothepage,thedevelopercanalsoplaceJSPscriptingelementsonthepage.ScriptingelementsaretagsthatencapsulatelogicthatisrecognizedbytheJSP.YoucaneasilypickoutscriptingelementsonJSPpagesbylookingforcodethatbeginswith<%andendswith%>.TobeseenasaJSPpage,thefilejustneedstobesavedwithanextensionof.jsp.WhenaclientrequeststheJSPpage,thecontainertranslatesthepageintoasourcecodefileforaJavaservletandcompilesthesourceintoaJavaclassfile—justasyouwoulddoifyouwerewritingaservletfromscratch.Atruntime,thecontainercanalsocheckthelastmodifieddateoftheJSPfileagainsttheclassfile.IftheJSPfilehaschangedsinceitwaslastcompiled,thecontainerwillretranslateandrebuildthepagealloveragain.ProjectmanagerscannowassignthepresentationlayertoHTMLdevelopers,whothenpassontheirworktoJavadeveloperstocompletethebusiness-logicportion.TheimportantthingtorememberisthataJSPpageisreallyjustaservlet.Anythingyoucandowithaservlet,youcandowithaJSP.JavaBeans:JavaBeansareJavaclasseswhichconformtoasetofdesignpatternsthatmakethemeasiertousewithdevelopmenttoolsandothercomponents.DEFINITIONAJavaBeanisareusablesoftwarecomponentwritteninJava.ToqualifyasaJavaBean,theclassmustbeconcreteandpublic,andhaveanoargumentconstructor.JavaBeansexposeinternalfieldsaspropertiesbyprovidingpublicmethodsthatfollowaconsistentdesignpattern.Knowingthatthepropertynamesfollowthispattern,otherJavaclassesareabletouseintrospectiontodiscoverandmanipulateJavaBeanproperties.TheJavaBeandesignpatternsprovideaccesstothebean’sinternalstatethroughtwoflavorsofmethods:accessorsareusedtoreadaJavaBean’sstate;mutatorsareusedtochangeaJavaBean’sstate.Mutatorsarealwaysprefixedwithlowercasetokensetfollowedbythepropertyname.Thefirstcharacterinthepropertynamemustbeuppercase.Thereturnvalueisalwaysvoid—mutatorsonlychangepropertyvalues;theydonotretrievethem.Themutatorforasimplepropertytakesonlyoneparameterinitssignature,whichcanbeofanytype.Mutatorsareoftennicknamedsettersaftertheirprefix.ThemutatormethodsignatureforaweightpropertyofthetypeDoublewouldbe:publicvoidsetWeight(Doubleweight)Asimilardesignpatternisusedtocreatetheaccessormethodsignature.Accessormethodsarealwaysprefixedwiththelowercasetokenget,followedbythepropertyname.Thefirstcharacterinthepropertynamemustbeuppercase.Thereturnvaluewillmatchthemethodparameterinthecorrespondingmutator.Accessorsforsimplepropertiescannotacceptparametersintheirmethodsignature.Notsurprisingly,accessorsareoftencalledgetters.Theaccessormethodsignatureforourweightpropertyis：publicDoublegetWeight()Iftheaccessorreturnsalogicalvalue,thereisavariantpattern.Insteadofusingthelowercasetokenget,alogicalpropertycanusetheprefixis,followedbythepropertyname.Thefirstcharacterinthepropertynamemustbeuppercase.Thereturnvaluewillalwaysbealogicalvalue—eitherbooleanorBoolean.Logicalaccessorscannotacceptparametersintheirmethodsignature.ThebooleanaccessormethodsignatureforanonpropertywouldbepublicbooleanisOn()ThecanonicalmethodsignaturesplayanimportantrolewhenworkingwithJava-Beans.OthercomponentsareabletousetheJavaReflectionAPItodiscoveraJavaBean’spropertiesbylookingformethodsprefixedbyset,is,orget.IfacomponentfindssuchasignatureonaJavaBean,itknowsthatthemethodcanbeusedtoaccessorchangethebean’sproperties.SunintroducedJavaBeanstoworkwithGUIcomponents,buttheyarenowusedwitheveryaspectofJavadevelopment,includingwebapplications.WhenSunengineersdevelopedtheJSPtagextensionclasses,theydesignedthemtoworkwithJavaBeans.T