城市公交查詢系統(tǒng)畢業(yè)設(shè)計 外文翻譯

外文翻譯城市公交查詢系統(tǒng)的設(shè)計與實現(xiàn)城市公交查詢系統(tǒng)的設(shè)計與實現(xiàn)城市公交查詢系統(tǒng)的設(shè)計與實現(xiàn)城市公交查詢系統(tǒng)的設(shè)計與實現(xiàn)學生姓名指導教師副教授合作指導教師專業(yè)名稱計算機科學與技術(shù)所在學院水產(chǎn)學院2009年6月1原文摘自LVARJACOBSONOBJECTORIENTEDSOFTWAREENGINEERING第1版北京人民郵電出版社，200510外文資料原文ASPNETPAGEOBJECTMODELSUMMARYLEARNABOUTTHEEVENTINGMODELBUILTAROUNDASPNETWEBPAGESANDTHEVARIOUSSTAGESTHATAWEBPAGEEXPERIENCESONITSWAYTOHTMLTHEASPNETHTTPRUNTIMEGOVERNSTHEPIPELINEOFOBJECTSTHATTRANSFORMTHEREQUESTEDURLINTOALIVINGINSTANCEOFAPAGECLASSFIRST,ANDINTOPLAINHTMLTEXTNEXTDISCOVERTHEEVENTSTHATCHARACTERIZETHELIFECYCLEOFAPAGEANDHOWCONTROLANDPAGEAUTHORSCANINTERVENETOALTERTHESTANDARDBEHAVIOR6PRINTEDPAGESINTRODUCTIONEACHREQUESTFORAMICROSOFTASPNETPAGETHATHITSMICROSOFTINTERNETINFORMATIONSERVICESIISISHANDEDOVERTOTHEASPNETHTTPPIPELINETHEHTTPPIPELINEISACHAINOFMANAGEDOBJECTSTHATSEQUENTIALLYPROCESSTHEREQUESTANDMAKETHETRANSITIONFROMAURLTOPLAINHTMLTEXTHAPPENTHEENTRYPOINTOFTHEHTTPPIPELINEISTHEHTTPRUNTIMECLASSTHEASPNETINFRASTRUCTURECREATESONEINSTANCEOFTHISCLASSPEREACHAPPDOMAINHOSTEDWITHINTHEWORKERPROCESSREMEMBERTHATTHEWORKERPROCESSMAINTAINSONEDISTINCTAPPDOMAINPEREACHASPNETAPPLICATIONCURRENTLYRUNNINGTHEHTTPRUNTIMECLASSPICKSUPANHTTPAPPLICATIONOBJECTFROMANINTERNALPOOLANDSETSITTOWORKONTHEREQUESTTHEMAINTASKACCOMPLISHEDBYTHEHTTPAPPLICATIONMANAGERISFINDINGOUTTHECLASSTHATWILLACTUALLYHANDLETHEREQUESTWHENTHEREQUESTISFORANASPXRESOURCE,THEHANDLERISAPAGEHANDLERNAMELY,ANINSTANCEOFACLASSTHATINHERITSFROMPAGETHEASSOCIATIONBETWEENTYPESOFRESOURCESANDTYPESOFHANDLERSISSTOREDINTHECONFIGURATIONFILEOFTHEAPPLICATIONMOREEXACTLY,THEDEFAULTSETOFMAPPINGSISDEFINEDINTHESECTIONOFTHEMACHINECONFIGFILEHOWEVER,THEAPPLICATIONCANCUSTOMIZETHELISTOFITSOWNHTTPHANDLERSINTHELOCALWEBCONFIGFILETHELINEBELOWILLUSTRATESTHECODETHATDEFINESTHEHTTPHANDLERFORASPXRESOURCESANEXTENSIONCANBEASSOCIATEDWITHAHANDLERCLASS,ORMOREINGENERAL,WITHAHANDLERFACTORYCLASSINALLCASES,THEHTTPAPPLICATIONOBJECTINCHARGEFORTHEREQUESTGETSANOBJECTTHATIMPLEMENTSTHEIHTTPHANDLERINTERFACEIFTHEASSOCIATIONRESOURCE/CLASSISRESOLVEDINTERMSOFAHTTPHANDLER,THENTHERETURNEDCLASSWILLIMPLEMENTTHEINTERFACEDIRECTLYIFTHERESOURCEISBOUNDTOAHANDLERFACTORY,ANEXTRASTEPISNECESSARYAHANDLERFACTORYCLASSIMPLEMENTSTHEIHTTPHANDLERFACTORYINTERFACEWHOSEGETHANDLERMETHODWILLRETURNANIHTTPHANDLERBASEDOBJECTHOWCANTHEHTTPRUNTIMECLOSETHECIRCLEANDPROCESSTHEPAGEREQUESTTHEIHTTPHANDLERINTERFACEFEATURESTHEPROCESSREQUESTMETHODBYCALLINGTHISMETHODONTHEOBJECTTHATREPRESENTSTHEREQUESTEDPAGE,THEASPNETINFRASTRUCTURESTARTSTHEPROCESSTHATWILLGENERATETHEOUTPUTFORTHEBROWSERTHEREALPAGECLASS2THETYPEOFTHEHTTPHANDLERFORAPARTICULARPAGEDEPENDSONTHEURLTHEFIRSTTIMETHEURLISINVOKED,ANEWCLASSISCOMPOSEDANDDYNAMICALLYCOMPILEDTOANASSEMBLYTHESOURCECODEOFTHECLASSISTHEOUTCOMEOFAPARSINGPROCESSTHATEXAMINESTHEASPXSOURCESTHECLASSISDEFINEDASPARTOFTHENAMESPACEASPANDISGIVENANAMETHATMIMICSTHEORIGINALURLFOREXAMPLE,IFTHEURLENDPOINTISPAGEASPX,THENAMEOFTHECLASSISASPPAGE_ASPXTHECLASSNAME,THOUGH,CANBEPROGRAMMATICALLYCONTROLLEDBYSETTINGTHECLASSNAMEATTRIBUTEINTHEPAGEDIRECTIVETHEBASECLASSFORTHEHTTPHANDLERISPAGETHISCLASSDEFINESTHEMINIMUMSETOFMETHODSANDPROPERTIESSHAREDBYALLPAGEHANDLERSTHEPAGECLASSIMPLEMENTSTHEIHTTPHANDLERINTERFACEUNDERACOUPLEOFCIRCUMSTANCES,THEBASECLASSFORTHEACTUALHANDLERISNOTPAGEBUTADIFFERENTCLASSTHISHAPPENS,FOREXAMPLE,IFCODEBEHINDISUSEDCODEBEHINDISADEVELOPMENTTECHNIQUETHATINSULATESTHECODENECESSARYTOAPAGEINTOASEPARATECORMICROSOFTVISUALBASICNETCLASSTHECODEOFAPAGEISTHESETOFEVENTHANDLERSANDHELPERMETHODSTHATACTUALLYCREATETHEBEHAVIOROFTHEPAGETHISCODECANBEDEFINEDINLINEUSINGTHETAGORPLACEDINANEXTERNALCLASSTHECODEBEHINDCLASSACODEBEHINDCLASSISACLASSTHATINHERITSFROMPAGEANDSPECIALIZESITWITHEXTRAMETHODSWHENSPECIFIED,THECODEBEHINDCLASSISUSEDASTHEBASECLASSFORTHEHTTPHANDLERTHEOTHERSITUATIONINWHICHTHEHTTPHANDLERISNOTBASEDONPAGEISWHENTHECONFIGURATIONFILEOFTHEAPPLICATIONCONTAINSAREDEFINITIONFORTHEPAGEBASETYPEATTRIBUTEINTHESECTIONTHEPAGEBASETYPEATTRIBUTEINDICATESTHETYPEANDTHEASSEMBLYTHATCONTAINSTHEBASECLASSFORPAGEHANDLERSDERIVEDFROMPAGE,THISCLASSCANAUTOMATICALLYENDOWHANDLERSWITHACUSTOMANDEXTENDEDSETOFMETHODSANDPROPERTIESTHEPAGELIFECYCLEONCETHEHTTPPAGEHANDLERCLASSISFULLYIDENTIFIED,THEASPNETRUNTIMECALLSTHEHANDLERSPROCESSREQUESTMETHODTOPROCESSTHEREQUESTNORMALLY,THEREISNONEEDTOCHANGETHEIMPLEMENTATIONOFTHEMETHODASITISPROVIDEDBYTHEPAGECLASSTHISIMPLEMENTATIONBEGINSBYCALLINGTHEMETHODFRAMEWORKINITIALIZE,WHICHBUILDSTHECONTROLSTREEFORTHEPAGETHEMETHODISAPROTECTEDANDVIRTUALMEMBEROFTHETEMPLATECONTROLCLASSTHECLASSFROMWHICHPAGEITSELFDERIVESANYDYNAMICALLYGENERATEDHANDLERFORANASPXRESOURCEOVERRIDESFRAMEWORKINITIALIZEINTHISMETHOD,THEWHOLECONTROLTREEFORTHEPAGEISBUILTNEXT,PROCESSREQUESTMAKESTHEPAGETRANSITVARIOUSPHASESINITIALIZATION,LOADINGOFVIEWSTATEINFORMATIONANDPOSTBACKDATA,LOADINGOFTHEPAGESUSERCODEANDEXECUTIONOFPOSTBACKSERVERSIDEEVENTSAFTERTHAT,THEPAGEENTERSINRENDERINGMODETHEUPDATEDVIEWSTATEISCOLLECTEDTHEHTMLCODEISGENERATEDANDTHENSENTTOTHEOUTPUTCONSOLEFINALLY,THEPAGEISUNLOADEDANDTHEREQUESTISCONSIDEREDCOMPLETELYSERVEDDURINGTHEVARIOUSPHASES,THEPAGEFIRESAFEWEVENTSTHATWEBCONTROLSANDUSERDEFINEDCODECANINTERCEPTANDHANDLESOMEOFTHESEEVENTSARESPECIFICFOREMBEDDEDCONTROLSANDSUBSEQUENTLYCANTBEHANDLEDATTHELEVELOFTHEASPXCODE3APAGETHATWANTSTOHANDLEACERTAINEVENTSHOULDEXPLICITLYREGISTERANAPPROPRIATEHANDLERHOWEVER,FORBACKWARDCOMPATIBILITYWITHTHEEARLIERVISUALBASICPROGRAMMINGSTYLE,ASPNETALSOSUPPORTSAFORMOFIMPLICITEVENTHOOKINGBYDEFAULT,THEPAGETRIESTOMATCHSPECIALMETHODNAMESWITHEVENTSIFAMATCHISFOUND,THEMETHODISCONSIDEREDAHANDLERFORTHEEVENTASPNETPROVIDESSPECIALRECOGNITIONOFSIXMETHODNAMESTHEYAREPAGE_INIT,PAGE_LOAD,PAGE_DATABIND,PAGE_PRERENDER,ANDPAGE_UNLOADTHESEMETHODSARETREATEDASHANDLERSFORTHECORRESPONDINGEVENTSEXPOSEDBYTHEPAGECLASSTHEHTTPRUNTIMEWILLAUTOMATICALLYBINDTHESEMETHODSTOPAGEEVENTSSAVINGDEVELOPERSFROMHAVINGTOWRITETHENECESSARYGLUECODEFOREXAMPLE,THEMETHODNAMEDPAGE_LOADISWIREDTOTHEPAGESLOADEVENTASIFTHEFOLLOWINGCODEWASWRITTENTHISLOADNEWEVENTHANDLERTHISPAGE_LOADTHEAUTOMATICRECOGNITIONOFSPECIALNAMESISABEHAVIORUNDERTHECONTROLOFTHEAUTOEVENTWIREUPATTRIBUTEOFTHEPAGEDIRECTIVEIFTHEATTRIBUTEISSETTOFALSE,ANYAPPLICATIONSTHATWISHTOHANDLEANEVENTNEEDTOCONNECTEXPLICITLYTOTHEPAGEEVENTPAGESTHATDONTUSEAUTOMATICEVENTWIREUPWILLGETASLIGHTPERFORMANCEBOOSTBYNOTHAVING51ASPXTODOTHEEXTRAWORKOFMATCHINGNAMESANDEVENTSYOUSHOULDNOTETHATALLMICROSOFTVISUALSTUDIONETPROJECTSARECREATEDWITHTHEAUTOEVENTWIREUPATTRIBUTEDISABLEDHOWEVER,THEDEFAULTSETTINGFORTHEATTRIBUTEISTRUE,MEANINGTHATMETHODSSUCHASPAGE_LOADARERECOGNIZEDANDBOUNDTOTHEASSOCIATEDEVENTTHEEXECUTIONOFAPAGECONSISTSOFASEQUENCEOFSTAGESLISTEDINTHEFOLLOWINGTABLEANDISCHARACTERIZEDBYAPPLICATIONLEVELEVENTSAND/ORPROTECTED,OVERRIDABLEMETHODSTABLE1KEYEVENTSINTHELIFEOFANASPNETPAGESTAGEPAGEEVENTOVERRIDABLEMETHODPAGEINITIALIZATIONINITVIEWSTATELOADINGLOADVIEWSTATEPOSTBACKDATAPROCESSINGLOADPOSTDATAMETHODINANYCONTROLTHATIMPLEMENTSTHEIPOSTBACKDATAHANDLERINTERFACEPAGELOADINGLOADPOSTBACKCHANGENOTIFICATIONRAISE51POSASPXTDATACHANGEDEVENTMETHODINANYCONTROLTHATIMPLEMENTSTHEIPOSTBACKDATAHANDLERINTERFACEPOSTBACKEVENTHANDLINGANYPOSTBACKEVENTDEFINEDBYCONTROLSRAISEPOSTBACKEVENTMETHODINANYCONTROLTHATIMPLEMENTSTHEIPOSTBACKEVENTHANDLERINTERFACEPAGEPRERENDERINGPHASEPRERENDERVIEWSTATESAVINGSAVEVIEWSTATE4PAGERENDERINGRENDERPAGEUNLOADINGUNLOADSOMEOFTHESTAGESLISTEDABOVEARENOTVISIBLEATTHEPAGELEVELANDAFFECTONLYAUTHORSOFSERVERCONTROLSANDDEVELOPERSWHOHAPPENTOCREATEACLASSDERIVEDFROMPAGEINIT,LOAD,PRERENDER,UNLOAD,PLUSALLPOSTBACKEVENTSDEFINEDBYEMBEDDEDCONTROLSARETHEONLYSIGNALSOFLIFETHATAPAGESENDSTOTHEEXTERNALWORLDSTAGESOFEXECUTIONTHEFIRSTSTAGEINTHEPAGELIFECYCLEISTHEINITIALIZATIONTHISSTAGEISCHARACTERIZEDBYTHEINITEVENT,WHICHFIRESTOTHEAPPLICATIONAFTERTHEPAGESCONTROLTREEHASBEENSUCCESSFULLYCREATEDINOTHERWORDS,WHENTHEINITEVENTARRIVES,ALLTHECONTROLSSTATICALLYDECLAREDINTHEASPXSOURCEFILEHAVEBEENINSTANTIATEDANDHOLDTHEIRDEFAULTVALUESCONTROLSCANHOOKUPTHEINITEVENTTOINITIALIZEANYSETTINGSTHATWILLBENEEDEDDURINGTHELIFETIMEOFTHEINCOMINGWEBREQUESTFOREXAMPLE,ATTHISTIMECONTROLSCANLOADEXTERNALTEMPLATEFILESORSETUPTHEHANDLERFORTHEEVENTSYOUSHOULDNOTICETHATNOVIEWSTATEINFORMATIONISAVAILABLEFORUSEYETIMMEDIATELYAFTERINITIALIZATION,THEPAGEFRAMEWORKLOADSTHEVIEWSTATEFORTHEPAGETHEVIEWSTATEISACOLLECTIONOFNAME/VALUEPAIRS,WHERECONTROLSANDTHEPAGEITSELFSTOREANYINFORMATIONTHATMUSTBEPERSISTENTACROSSWEBREQUESTSTHEVIEWSTATEREPRESENTSTHECALLCONTEXTOFTHEPAGETYPICALLY,ITCONTAINSTHESTATEOFTHECONTROLSTHELASTTIMETHEPAGEWASPROCESSEDONTHESERVERTHEVIEWSTATEISEMPTYTHEFIRSTTIMETHEPAGEISREQUESTEDINTHESESSIONBYDEFAULT,THEVIEWSTATEISSTOREDINAHIDDENFIELDSILENTLYADDEDTOTHEPAGETHENAMEOFTHISFIELDIS_VIEWSTATEBYOVERRIDINGTHELOADVIEWSTATEMETHODAPROTECTEDOVERRIDABLEMETHODONTHECONTROLCLASSCOMPONENTDEVELOPERSCANCONTROLHOWTHEVIEWSTATEISRESTOREDANDHOWITSCONTENTSAREMAPPEDTOTHEINTERNALSTATEMETHODSLIKELOADPAGESTATEFROMPERSISTENCEMEDIUMANDITSCOUNTERPARTSAVEPAGESTATETOPERSISTENCEMEDIUMCANBEUSEDTOLOADANDSAVETHEVIEWSTATETOANALTERNATIVESTORAGEMEDIUMFOREXAMPLE,SESSION,DATABASES,ORASERVERSIDEFILEUNLIKELOADVIEWSTATE,THEAFOREMENTIONEDMETHODSAREAVAILABLEONLYINCLASSESDERIVEDFROMPAGEONCETHEVIEWSTATEHASBEENRESTORED,THECONTROLSINTHEPAGETREEAREINTHESAMESTATETHEYWERETHELASTTIMETHEPAGEWASRENDEREDTOTHEBROWSERTHENEXTSTEPCONSISTSOFUPDATINGTHEIRSTATETOINCORPORATECLIENTSIDECHANGESTHEPOSTBACKDATAPROCESSINGSTAGEGIVESCONTROLSACHANCETOUPDATETHEIRSTATESOTHATITACCURATELYREFLECTSTHESTATEOFTHECORRESPONDINGHTMLELEMENTONTHECLIENTFOREXAMPLE,ASERVERTEXTBOXCONTROLHASITSHTMLCOUNTERPARTINANELEMENTINTHEPOSTBACKDATASTAGE,THETEXTBOXCONTROLWILLRETRIEVETHECURRENTVALUEOFTAGANDUSEITTOREFRESHITSINTERNALSTATEEACHCONTROLISRESPONSIBLEFOREXTRACTINGVALUESFROMPOSTEDDATAANDUPDATINGSOMEOFITSPROPERTIESTHETEXTBOXCONTROLWILLUPDATEITSTEXTPROPERTYWHEREASTHECHECKBOXCONTROLWILLREFRESHITSCHECKEDPROPERTYTHEMATCHBETWEENASERVERCONTROLANDAHTMLELEMENTISFOUNDONTHEIDOFBOTHATTHEENDOFTHEPOSTBACKDATAPROCESSINGSTAGE,ALLCONTROLSINTHEPAGEREFLECTTHEPREVIOUSSTATE5UPDATEDWITHCHANGESENTEREDONTHECLIENTATTHISPOINT,THELOADEVENTISFIREDTOTHEPAGETHEREMIGHTBECONTROLSINTHEPAGETHATNEEDTOACCOMPLISHCERTAINTASKSIFASENSITIVEPROPERTYISMODIFIEDACROSSTWODIFFERENTREQ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TML代碼然后將其發(fā)送到輸出控制臺。最后，卸載頁面，并認為已完成對該請求的處理。在各個階段中，頁面都會激發(fā)一些WEB控件和用戶定義的代碼所能截獲并處理的事件。其中的一些事件是嵌入式控件專用的，因而并不能在ASPX代碼級進行處理。如果頁面想要處理某個事件，它應(yīng)該顯式地注冊相應(yīng)的處理程序。然而，為了向后兼容早期的VISUALBASIC編程風格，ASPNET也支持一種隱式的事件掛起形式。在默認情況下，頁面將嘗試把特定的方法名與事件匹配起來；如果找到匹配的方法，就認為該方法是該事件的處理程序。ASPNET提供了六個方法名的特定識別。它們是PAGE_INIT、PAGE_LOAD、PAGE_DATABIND、PAGE_PRERENDER和PAGE_UNLOAD。這些方法被當作是PAGE類所提供的相應(yīng)事件的處理程序。HTTP運行時將自動把這些方法與頁面事件綁定起來，這樣一來，開發(fā)人員就不必編寫所需的粘接代碼。例如，名為PAGE_LOAD的方法與頁面的LOAD事件綁定，就像已編寫以下代碼一樣。THISLOADNEWEVENTHANDLERTHISPAGE_LOAD這種自動識別特殊名稱的功能由PAGE指令的AUTOEVENTWIREUP屬性控制。如果將該屬性設(shè)置為FALSE，則任何想要處理某個事件的應(yīng)用程序都需顯式地連接到該頁面事件。如果頁面不使用自動事件關(guān)聯(lián)功能，就不必進行額外的操作以匹配各名稱和事件，從而其性能也稍有提升。應(yīng)該注意的是，所有的MICROSOFTVISUALSTUDIONET項目在創(chuàng)建時都禁用了AUTOEVENTWIREUP屬性。然而，此屬性的默認設(shè)置為TRUE，意味著諸如PAGE_LOAD等方法會被識別并被綁定到相關(guān)的事件。頁面的執(zhí)行過程包括下面表格中所列的一系列階段，并以具有一些應(yīng)用程序級事件和/或受保護且可重寫的方法為特征。8表格1ASPNET頁面生存周期中的關(guān)鍵事件階段頁面事件可重寫方法頁面初始化INIT加載視圖狀態(tài)LOADVIEWSTATE處理回發(fā)數(shù)據(jù)實現(xiàn)IPOSTBACKDATAHANDLER接口的任何控件中的LOADPOSTDATA方法加載頁面LOAD回發(fā)更改通知實現(xiàn)IPOSTBACKDATAHANDLER接口的任何控件中的RAISEPOSTDATACHANGEDEVENT方法處理回發(fā)事件控件所定義的任何回發(fā)事件實現(xiàn)了IPOSTBACKEVENTHANDLER接口的任何控件的RAISEPOSTBACKEVENT方法頁面呈現(xiàn)前階段PRERENDER保存視圖狀態(tài)SAVEVIEWSTATE呈現(xiàn)頁面RENDER卸載頁面UNLOAD在頁面級上，以上所列的某些階段是不可見的，并僅影響服務(wù)器控件編寫者和那些湊巧要創(chuàng)建從PAGE派生的類的開發(fā)人員。頁面向外界發(fā)送的活動信號僅包括INIT、LOAD、PRERENDER、UNLOAD以及嵌入式控件所定義的所有回發(fā)事件。執(zhí)行的各個階段頁面生存周期中的第一個階段是初始化。這一階段的標志就是INIT事件，在成功創(chuàng)建頁面的控件樹后，對應(yīng)用程序激發(fā)這個事件。換而言之，當INIT事件發(fā)生時，在ASPX源文件中靜態(tài)聲明的所有控件都已實例化并取其默認值。控件可掛起INIT事件，以便初始化在傳入的WEB請求的生存周期中所需的任何設(shè)置。例如，此時控件可以加載外部模板文件或設(shè)置各個事件的處理程序。應(yīng)該注意到，這時還沒有視圖狀態(tài)信息可供使用。在初始化之后，頁面框架立即加載該頁面的視圖狀態(tài)。所謂視圖狀態(tài)就是一些名稱/值對的集合，控件和頁面本身可將那些對所有WEB請求都必須始終有效的任何信息存儲在其中。視圖狀態(tài)表示頁面的調(diào)用上下文。一般情況下，其中包含上次在服務(wù)器中處理該頁面時各控件的狀態(tài)。首次在會話中請求頁面時，視圖狀態(tài)為空。在默認情況下，視圖狀態(tài)被存儲在一個隱藏字段中，而該字段是自行添加到頁面中的。該字段名稱為_VIEWSTATE。通過重寫