外文原文0VERVIEWOFJAVASERVLETSSERVLETSAREPROTOCOLANDPLATFORMINDEPENDENTSERVERSIDECOMPONENTSWRITTENINJAVA，WHICHDYNAMICALLYEXTENDJAVAENABLEDSERVERSTHEYPROVIDEAGENERALFRAMEWORKFORSERVICESBUILTUSINGTHEREQUESTRESPONSEPARADIGM。THEIRINITIALUSEISTOPROVIDESECUREWEBBASEDACCESSTODATAWHICHISPRESENTEDUSINGHTMLWEBPAGES，INTERACTIVELYVIEWINGORMODIFYINGTHATDATAUSINGDYNAMICWEBPAGEGENERATIONTECHNIQUESSINCESERVLETSRUNINSIDESERVERS，THEYDONOTNEEDAGRAPHICALUSERINTERFACEOTHERWISE，THEYARETHESERVERSIDECOUNTERPARTTOAPPLETSWHICHAREUSEDONLYONTHECLIENTSIDEOFSYSTEMSTHEYAREJAVAAPPLICATIONCOMPONENTSWHICHAREDOWNLOADED，ONDEMAND，TOTHEPARTOFTHESYSTEMWHICHNEEDSTHEMFIGURE1CLIENTSTALKINGTOJAVASERVLETSINSERVERSCLIENTSMAYRANGEINCOMPLEXITYFROMSIMPLEHTMLFORMSTOSOPHISTICATEDJAVAAPPLETSSERVLETSWILLFREQUENTLYUSESOMEKINDOFPERSISTENTSTORAGE，SUCHASFILESORADATABASESERVLETSAREMOSTOFTENPROVIDEDBYORGANIZATIONSWHICHPROVIDECUSTOMIZEDMULTIUSERSERVICESTOTHEIRCUSTOMERBASESHOWEVER，SERVLETSAREALSOFLEXIBLEENOUGHTOSUPPORTSTANDARDIZEDSERVICESSUCHASSERVINGSTATICWEBPAGESTHROUGHTHEHTTPORHTTPSPROTOCOLS，ANDPROXYINGSERVICESSINCETHEYAREUSEDFORDYNAMICEXTENSIBILITY，THEYMAYBEUSEDINAPLUGINSTYLE，SUPPORTINGFACILITIESSUCHASSEARCHENGINESANDSEMICUSTOMAPPLICATIONSSERVLETSALSOPROVIDEASTRONGPLATFORMFORSEMICUSTOMAPPLICATIONS，SUCHASWEBBASEDORDERENTRYORINVENTORYSYSTEMSALTHOUGHALLSERVLETSAREWRITTENINJAVA，THEIRCLIENTSMAYBEWRITTENINANYLANGUAGEWHENSERVLETSAREUSEDINTHEMIDDLETIERSOFDISTRIBUTEDAPPLICATIONSYSTEMS，THEYCANINTURNBECLIENTSTOOTHERSERVICES，WRITTENINANYLANGUAGEFOREXAMPLESERVLETSCANUSEJDBCTOCONTACTANAPPLICATIONSHIGHLYTUNEDRELATIONALDATABASESCOMMUNICATINGWITHOTHERKINDSOFCURRENTORLEGACYSYSTEMSMAYCALLFORALTERNATESOFTWAREPACKAGES，ASREQUIREDBYTHOSESYSTEMSMANYWAYSTOUSESERVLETSAFEWOFTHEMANYAPPLICATIONSFORSERVLETSINCLUDEASIMPLESERVLETCANPROCESSDATAWHICHWASPOSTEDOVERHTTPSUSINGANHTMLFORM，PASSINGDATASUCHASAPURCHASEORDERWITHCREDITCARDDATATHISWOULDBEPARTOFANORDERENTRYANDPROCESSINGSYSTEM，WORKINGWITHPRODUCTANDINVENTORYDATABASESANDPERHAPSANONLINEPAYMENTSYSTEMSINCESERVLETSHANDLEMULTIPLEREQUESTSCONCURRENTLY，THEREQUESTSCANBESYNCHRONIZEDWITHEACHOTHERTOSUPPORTCOLLABORATIVEAPPLICATIONSSUCHASONLINECONFERENCINGONECOULDDEFINEACOMMUNITYOFACTIVEAGENTS，WHICHSHAREWORKAMONGEACHOTHERTHECODEFOREACHAGENTWOULDBELOADEDASASERVLET，ANDTHEAGENTSWOULDPASSDATATOEACHOTHERONESERVLETCOULDFORWARDREQUESTSOTHERSERVERSTHISTECHNIQUECANBALANCELOADAMONGSEVERALSERVERSWHICHMIRRORTHESAMECONTENTOR，ITCOULDBEUSEDTOPARTITIONASINGLELOGICALSERVICEBETWEENSEVERALSERVERS，ROUTINGREQUESTSACCORDINGTOTASKTYPEORORGANIZATIONALBOUNDARIESAPIAVAILABILITY_JTHEJAVASERVLETAPIISASTANDARDJAVAEXTENSIONAPITHISMEANSTHATWHILEITISNOTPARTOFTHECOREJAVAFRAMEWORKWHICHMUSTALWAYSBEPARTOFALLPRODUCTSBEARINGTHEJAVABRAND，ITWILLBEMADEAVAILABLEWITHSUCHPRODUCTSBYTHEIRVENDORSASANADDONPACKAGESUNHASPROVIDEDAPACKAGEWHICHMAYBEUSEDTOEMBEDSERVLETSUPPORTINOTHERWEBSERVERS，INCLUDINGAPACHEANDDERIVEDSERVERSSUCHASSTRONGHOLDNETSCAPEFASTTRACKANDENTERPRISESERVERS，ANDMICROSOFTSIISSERVLETSWEREINITIALLYSUPPORTEDINTHEJAVAWEBSERVERFROMSUNSINCETHEN，ANUMBEROFOTHERJAVABASEDWEBSERVERSHAVESUPPORTEDTHEAPI，ORCOMMITTEDTOSUPPORTINGITFEATURESOFTHEJAVASERVLETAPITHESERVLETAPIISALREADYSUPPODEDBYMOSTJAVABASEDWEBSERVERS,ANDIMPLEMENTALIONSAREAVAILABLEFOROTHERPOPULARWEBSERVERSTHISMEANSTHATYOUGETTHEJAVAADVANTAGEWHENYOUUSETHESERVLETAPINOTONLYWILLYOURCODENOTHAVEMEMORYLEAKSANDSUFFERFROMHARDTOFINDPOINTERBUGS。BUTYOURCODERUNSONPLATFORMSFROMMANYSERVERVENDORSYOUDONTNEEDTOLOCKYOURSELFINTOASINGLEVENDORSERVEREXTENSIONAPI，USINGERRORPRONELANGUAGESSUCHASCORSCRIPTINGLANGUAGESINSTEAD，YOUCANDOALLOFYOURSERVERANDCLIENTDEVELOPMENTINASINGLEDEVELOPMENTLANGUAGENOLONGERDOESYOURTEAMNEEDTOJUGGLEMULTIPLELANGUAGES，ANDCOPEWITHTHEMAINTAINABILITYPROBLEMSINHERENTINSCRIPTINGLANGUAGESNOLONGERDOYOURWEBBASEDAPPLICATIONSNEEDTOSUFFERTHEPERFORMANCEANDPORTABILITYPENALTIESOFCGIJAVAISTHEPROFESSIONALPROGRAMMINGTOOLYOUNEEDTOPROVIDEROBUSTSERVERSOLUTIONSTHISSECTIONPROVIDESYOUANOVERVIEWOFTHEKEYFEATURESOFJAVASERVLETS，ADDRESSINGTHESEMAINTOPICSWHATDOSERVLETSLOOKLIKESERVLETLIFECYCLESECURITYFEATURESHTMLAWARESERVLETSHTTPSPECIFICSERVLETSPERFORMANCEFEATURESWHATDOSERVLETSLOOKLIKESERVLETSSUPPORTTHEFAMILIARPROGRAMMINGMODELOFACCEPTINGREQUESTSANDGENERATINGRESPONSESTHISMODELISUSEDWITHAVARIETYOFDISTRIBUTEDSYSTEMPROGRAMMINGTOOLSETS，RANGINGFROMREMOTEPROCEDURECALLSTOTHEHTTPREQUESTSMADETOWEBSERVERSSERVLETSIMPLEMENTTHESERVLETINTERFACE，USUALLYBYEXTENDINGEITHERTHEGENERICORANHTTPSPECIFICIMPLEMENTATIONTHESIMPLESTPOSSIBLESERVLETDEFINESASINGLEMETHOD，SERVICETHESERVICEMETHODISPROVIDEDWITHREQUESTANDRESPONSEPARAMETERSTHESEENCAPSULATEFHEDATASENTBYTHECLIENT，PROVIDINGACCESSTOPARAMETERSANDALLOWINGSERVLETSTOREPODSTATUSINCLUDINGERRORSSERVLETSNORMALLYRETRIEVEMOSTOFTHEIRPARAMETERSTHROUGHANINPUTSTREAM，ANDSENDTHEIRRESPONSESSINGANOUTPUTSTREAM、THESEINPUTANDOUTPUTSTREAMSMAYBEUSEDWITHDATANWHATEVERFORMATISAPPROPRIATEFOREXAMPLEANAPPLETANDSERVICEMIGHTEXCHANGEDATAUSINGOBJECTSERIALIZATION；HTML，ANDNUMEROUSIMAGEFORMATS，MAYALSOBEAPPROPRIATEDATAFORMATSSERVLETANDENVIRONMENTSTATESINCESERVLETSAREJAVAOBJECTS，THEYHAVEINSTANCESPECIFICDATATHISMEANSTHATINEFFECTSERVLETSAREINDEPENDENTAPPLICATIONSRUNNINGWITHINSERVERS，WITHOUTNEEDINGTHECOMPLEXITYOFADDITIONALCLASSESWHICHAREREQUIREDBYSOMEALTERNATIVESERVEREXTENSIONAPLSSERVLETSHAVEACCESSTOSOMESERVLETSPECIFICCONFIGURATIONDATAATINITIALIZATIONTIMETHISALLOWSDIFFERENTINSTANCESOFTHESAMESERVLETCLASSTOBEINITIALIZEDWITHDIFFERENTDATA,ANDBEMANAGEDASDIFFERENTLYNAMEDSERVLETSTHEDATAPROVIDEDATINITIALIZATIONTIMEWOULDINCLUDEANAREAWHEREEACHINSTANCEWOULDKEEPITSPERSISTENTINSTANCESPECIFICSTATESERVLETSALSOHAVETHEABILITYTOINTERACTWITHTHEIRENVIRONMENTTHROUGHASERVLETCONTEXTOBJECT1LL一SERVLETLIFECYCLESERVLETSAREAWAYSDYNAMICALLYLOADED，ALTHOUGHSERVERSWILLUSUALLYPROVIDEANADMINISTRATIVEOPTIONTOFORCELOADINGANDINITIALIZINGPARTICULARSERVLETSWHENTHESERVERSTARTSUPSERVLETSARELOADEDUSINGNORMALJAVACLASS10ADINGFACILITIES，WHICHMEANSTHATTHEYMAYBELOADEDFROMREMOTEDIRECTORIESFOREXAMPLE，ATRUSTEDHTTPSDEPARTMENTSERVLETSDIRECTORYASEASILYASFROMTHELOCALFILESYSTEMTHISALLOWSFORINCREASEDFLEXIBILITYINSYSTEMARCHITECTUREANDEASIERDISTRIBUTIONOFSERVICESINANETWORKWHENARESERVLETSLOADEDSERVERSALSOVARYINHOWTHEYKNOWWHENTOLOADSERVLETSWHENAREQUESTCOMESIN，THESERVERKNOWSHOWTOMAPITTOASERVLET，WHICHMAYFIRSTNEEDTOBELOADEDTHATMAPPINGWILLUSUALLYBEDONEINONE0FTHESECOMMONWAYSSERVERADMINISTRATORSMIGHTSPECIFYTHATSOMEKINDSOFCLIENTREQUESTSALWAYSMAPTOAPARTICULARSERVLETFOREXAMPLE，ONEWHICHTALKSTOAPARTICULARDATABASESERVERADMINISTRATORSMIGHTSPECIFYTHATPARTOFTHECLIENTREQUESTISTHENAMEOFTHESERVLETASFOUNDINANADMINISTEREDSERVLETSDIRECTORYATMANYSITES，THATDIRECTORYWOULDBESHAREDBETWEENSERVERSWHICHSHARETHELOADOFPROCESSINGFORTHESITESCLIENTSSOMESERVERSMAYBEABLETOAUTOMATICALLYINVOKESERVLETSTOFILTERTHEOUTPUTOFOTHERSERVLETSBASEDONTHEIRADMINISTRATIVECONFIGURATIONFOREXAMPLE，PARTICULARTYPESOFSERVLETOUTPUTMAYTRIGGERPOSTPROCESSINGBYOTHERSERVLETS,PERHAPSTOPERFORMFORMATCONVERSIONSPROPERLYAUTHORIZEDCLIENTSMIGHTSPECIFYTHESERVLETWHICHISTOBEINVOKED，WITHOUTADMINISTRATIVEINTERVENTIONSECURITYFEATURESSERVLELSHAVEACCESSTOINFORMATIONABOUTTHEIRCLIENTSWHENUSEDWITHSECUREPROTOCOLSSUCHASSSLPEERIDENTITIESCANBEDETERMINEDRELIABLYSERVLETSRELYINGONHTTPALSOHAVEACCESSTOHTTPSPECIFICAUTHENTICATIONDATASERVLETSHAVETHEJAVAADVANTAGEMEMORYACCESSVIOLATIONSANDSTRONGTYPINGVIOLATIONSARENOTPOSSIBLE,SOTHATFAULTYSERVLETSWILLNOTCARVERSTHEWAYTHATISCOMMONINMOSTCLANGUAGESERVEREXTENSIONENVIRONMENTUNLIKEANYOTHERCURRENTSERVEREXTENSIONAPIJAVASERVLETSPROVIDESTRONGSECURITYPOLICYSUPPORTTHISISBECAUSEALLJAVAENVIRONMENTSPROVIDEASECURITYMANAGERWHICHCANBEUSEDTOCONTROLWHETHERACTIONSSUCHASNETWORKORFILEACCESSARETOBEPERMITTEDBYDEFAULT，ALLSERVLETSAREUNTRUSTED，ANDARENOTALLOWEDTOPERFORMOPERATIONSSUCHASACCESSINGNETWORKSERVICESORLOCALFILESHOWEVER、SERVLETS“BUILTINTO”THESERVER,ORSERVLETSWHICHHAVEBEENDIGITALLYSIGNEDASTHEYWEREPUTINTOJAVAARCHIVEJARFILES，MAYBETRUSTEDANDGRANTEDMOREPERMISSIONSBYTHESECURITYMANAGERADIGITALSIGNATUREONEXECUTABLECODEINDICATESTHATTHEORGANIZATIONWHICHSIGNEDTHECODE”VOUCHESFORIT”INSOMESENSESUCHSIGNATURESCANTSUPPORTACCOUNTABILITYBYTHEMSELVES，BUTTHEYDOINDICATEADEGREEOFASSURANCETHATMAYBEPLACEDONUSEOFTHATCODEFOREXAMPLE，APARTICULARSIGNATUREFROMAMISORGANIZATIONMIGHTBEREQUIREDONALLCODEWHICHISGRANTEDGENERALACCESSTONETWORKSERVICESWITHINACORPORATEINTRANETTHATSIGNATUREMIGHTONLYBEUSEDONCODEWHICHISSTRONGLYBELIEVEDNOTTOVIOLATEPARTICULARSECURITYPOLICIESWEBAPPLICATIONLIFECYCLEAWEBAPPLICATIONCONSISTSOFWEBCOMPONENTS，STATICRESOURCEFILESSUCHASIMAGES，ANDHELPERCLASSESANDLIBRARIESTHEWEBCONTAINERPROVIDESMANYSUPPORTINGSERVICESTHATENHANCETHECAPABILITIESOFWEBCOMPONENTSANDMAKETHEMEASIERTODEVELOPHOWEVER，BECAUSEAWEBAPPLICATIONMUSTTAKETHESESERVICESINTOACCOUNT，THEPROCESSFORCREATINGANDRUNNINGAWEBAPPLICATIONISDIFFERENTFROMTHATOFTRADITIONALSTANDALONEJAVACLASSESTHEPROCESSFORCREATING，DEPLOYING，ANDEXECUTINGAWEBAPPLICATIONCANBESUMMARIZEDASFOLLOWS1DEVELOPTHEWEBCOMPONENTCODE2DEVELOPTHEWEBAPPLICATIONDEPLOYMENTDESCRIPTOR3COMPILETHEWEBAPPLICATIONCOMPONENTSANDHELPERCLASSESREFERENCEDBYTHECOMPONENTS4OPTIONALLYPACKAGETHEAPPLICATIONINTOADEPLOYABLEUNIT、5DEPLOYTHEAPPLICATIONINTOAWEBCONTAINER6ACCESSAURLTHATREFERENCESTHEWEBAPPLICATIONWEBMODULESINTHEJAVAEEARCHITECTURE，WEBCOMPONENTSANDSTATICWEBCONTENTFILESSUCHASIMAGESARECALLEDWEBRESOURCESAWEBMODULEISTHESMALLESTDEPLOYABLEANDUSABLEUNITOFWEBRESOURCESAJAVAEEWEBMODULECORRESPONDSTOAWEBAPPLICATIONASDEFINEDINTHEJAVASERVLETSPECIFICATIONINADDITIONTOWEBCOMPONENTSANDWEBRESOURCES，AWEBMODULECANCONTAINOTHERFILES。SERVERSIDEUTILITYCLASSESDATABASEBEANS，SHOPPINGCARTS，ANDSOONOFTENTHESECLASSESCONFORMTOTHEJAVABEANSCOMPONENTARCHITECTURE。CLIENTSIDECLASSESAPPLETSANDUTILITYCLASSESAWEBMODULEHASASPECIFICSTRUCTURETHETOPLEVELDIRECTORYOFAWEBMODULEISTHEDOCUMENTROOTOFTHEAPPLICATIONTHEDOCUMENTROOTISWHEREJSPPAGES，CLIENTSIDECLASSESANDARCHIVES，ANDSTATICWEBRESOURCES，SUCHASIMAGES，ARESTOREDTHEDOCUMENTROOTCONTAINSASUBDIRECTORYNAMEDWEBINF，WHICHCONTAINSTHEFOLLOWINGFILESANDDIRECTORIES。WEBXMLTHEWEBAPPLICATIONDEPLOYMENTDESCRIPTOR。TAGLIBRARYDESCRIPTORFILESSEETAGLIBRARYDESCRIPTORS，PAGE220CLASSESADIRECTORYTHATCONTAINSSERVERSIDECLASSESSERVLETS，UTILITYCLASSES，ANDJAVABEANSCOMPONENTS。TAGSADIRECTORYTHATCONTAINSTAGFILES，WHICHAREIMPLEMENTATIONSOFTAGLIBRARIESSEETAGFILELOCATION，PAGE205LIBADIRECTORYTHATCONTAINSJARARCHIVESOFLIBRARIESCALLEDBYSERVERSIDECLASSESIFYOURWEBMODULEDOESNOTCONTAINANYSERVLETS，F(xiàn)ILTER，ORLISTENERCOMPONENTSTHENITDOESNOTNEEDAWEBAPPLICATIONDEPLOYMENTDESCRIPTOR1NOTHERWORDS，IFYOURWEBMODULEONLYCONTAINSJSPPAGESANDSTATICFILESTHENYOUARENOTREQUIREDTOINCLUDEAWEBXMLFILETHEHELLOLEXAMPLEFIRSTDISCUSSEDINPACKAGINGWEBMODULES，CONTAINSONLYJSPPAGESANDIMAGESANDTHEREFOREDOESNOTINCLUDEADEPLOYMENTDESCRIPTORYOUCANALSOCREATEAPPLICATIONSPECIFICSUBDIRECTORIESTHATIS，PACKAGEDIRECTORIESINEITHERTHEDOCUMENTROOTORTHEWEBINFCLASSESDIRECTORYAWEBMODULECANBEDEPLOYEDASANUNPACKEDFILESTRUCTUREORCANBEPACKAGEDINAJARFILEKNOWNASAWEBARCHIVEWARFILEBECAUSETHECONTENTSANDUSEOFWARFILESDIFFERFROMTHOSEOFJARFILESWARFILENAMESUSEAWAREXTENSIONTHEWEBMODULEJUSTDESCRIBEDISPORTABLE；YOUCANDEPLOYITINTOANYWEBCONTAINERTHATCONFORMSTOTHEJAVASERVLETSPECIFICATIONTODEPLOYAWARONTHEAPPLICATIONSERVER，THEFILEMUSTALSOCONTAINARUNTIMEDEPLOYMENTDESCRIPTORTHERUNTIMEDEPLOYMENTDESCRIPTORISANXMLFILETHATCONTAINSINFORMATIONSUCHASTHECONTEXTROOTOFTHEWEBAPPLICATIONANDTHEMAPPINGOFTHEPORTABLENAMESOFANAPPLICATION。SRESOURCESTOTHEAPPLICATIONSERVERSRESOURCESTHEAPPLICATIONSERVERWEBAPPLICATIONRUNTIMEDDISNAMEDSUNNWEBXMLANDISLOCATEDINWEBINFALONGWITHTHEWEBAPPLICATIONDDPACKAGINGWEBMODULESAWEBMODULEMUSTBEPACKAGEDINTOAWARINCERTAINDEPLOYMENTSCENARIOSANDWHENEVERYOUWANTTODISTRIBUTETHEWEBMODULEYOUPACKAGEAWEBMODULEINTOAWARBYEXECUTINGTHEJARCOMMANDINADIRECTORYLAIDOUTNTHEFORMATOFAWEBMODULEORBYUSINGTHEANTUTILITYTHISTUTORIALALLOWSYOUTOUSETHESECONDAPPROACHTOBUILDTHEHELLOLAPPLICATION，F(xiàn)OLLOWTHESESTEPSINATERMINALWINDOW，GOTOJAVAEETUTORIAL5EXAMPLESWEBHELL。1RUNANTTHISTARGETWILLSPAWNANYNECESSARYCOMPILATIONS，COPYFILESTOTHEJAVAEETUTORIAL5EXAMPLESWEBHELLOLBUILDDIRECTORY，CREATETHEWARFILE，ANDCOPYITTOTHEJAVAEETUTORIAL5EXAMPLESWEBHELL01DISTDIRECTORYDEPLOYINGAWARFILEYOUCANDEPLOYAWARFILETOTHEAPPLICATIONSERVERINAFEWWAYSCOPYINGTHEWARINTOTHEDOMAINSDOMAINLAUTODEPLOYDIRECTORYUSINGTHEADMINCONSOLEBYRUNNINGASADMINORANTTODEPLOYTHEWARALLTHEREMETHODSAREDESCRIBEDBRIEFLYINTHISCHAPTERHOWEVER,THROUGHOUTTHETUTORIAL,WEUSEANTFORPACKAGINGANDDEPLOYINGSETTINGTHECONTEXTROOTACONTEXTROOTIDENTIFIESAWEDAPPLICATIONINAJAVAEESERVERYOUSEPECIFYTHECONTEXTROOTWHENYOUDEPLOYAWEDMODULEACONTEXTROOTMUSTSTARTWHIHAFORWARDSLASH/ANDENDWITHASTRINGINAPACKAGETWEBMODULEFORDEPLOYMENTONTHEAPPLICATIONSERVER,THECNTEXTROOTISSTOREDINSUNWEBXMLDEPLOYINGAPACKAGETWEBMODULEIFYOUHAVEDEPLOYEDTHEHELLOLAPPLICATION,BEFOREPROCEEDINGWITHWHISSECTIONG,UNDEPLOYTHEAPPLICATIONGBYFOLLOWINGONEOFTHEPROCEDURESDESCRBEDINUNDEPLOYINGWEBMODULESDEPLOYINGWITHTHEADMINCONSOLE1EXPANDTHEAPPLICATIONSNODE2SELECTTHEWEBAPPLICATIONGSNODE3CLICKTHEDEPLOYBUTTON4SELECTTHERADIOBUTTONLABELED“PACKAGEFILETOBEUPLOADTOTHEAPPLICATIONSERVER“5TYPETHEFULLPATHTOTHEWARFILEORCLICKONBROWSETOFINDIT,ANDTHENCLICKTHEOKBUTTON6CLICKNEXT7TYPETHEAPPLICATIONNAME8TYPETHECONTEXTROOT9SELECTTHEENABLEDBOX10CLICKTHEFINISHBUTTONDEPLOYINGWITHASADMINTODEPLOYAWARWITHASADMIN,PENATERMINALWINDOWORCOMMANDPROMPTANDEXECUTEASADMINDEPLOYFULLPATHTOWARFILEDEPLOYINGWITHANTTODEPLOYAWARWITHANT,OPENATERMINALWINDOWORCOMMANDPROMPTINTHEDIRECTORYWHEREYOUBUILTANDPACKAGEDTHEWAR,ANDEXECUTEANTDEPLOYTESTINGDEPLOYEDWEBMODULES中文翻譯JAVASERVLETS的概要SERVLET是數(shù)據(jù)正議定書和平臺(tái)獨(dú)立的服務(wù)器端組件的集合JAVA編寫的，動(dòng)態(tài)擴(kuò)展的JAVA功能服務(wù)器向他們提供了一個(gè)總體框架，為服務(wù)建成使用提供范式，他們的初步使用，提供WEB基礎(chǔ)數(shù)據(jù)的安全獲取，這是介紹了利用HTML網(wǎng)頁，你交互式地觀看或修改數(shù)據(jù)用動(dòng)態(tài)網(wǎng)頁的技術(shù)。由于SERVLET是運(yùn)行在服務(wù)器內(nèi)的，他們并不需要一個(gè)圖形用戶界面，否則，他們是服務(wù)器端對(duì)應(yīng)應(yīng)用程序（即只用對(duì)客戶端的系統(tǒng)）它們是應(yīng)用組件是下載完成后，對(duì)需求，以系統(tǒng)的一部分，這也需要它們圖1客戶交談的JAVASERVLET是在SERVERSCLIENTS范圍可以在復(fù)雜，從簡單的HTML形式，以先進(jìn)的JAVAAPPLETSSERVLETS將經(jīng)常使用的一些種持久性存儲(chǔ)，如檔案或資料庫。SERVLET是最常見的組織提供的，提供個(gè)性化的多用戶服務(wù)，以自己的顧客BASESHOWEVER，SERVLET，也有足夠的靈活性，以支持標(biāo)準(zhǔn)化服務(wù)，如在職靜態(tài)網(wǎng)頁是通過HTTP的（或HTTPS）協(xié)議，并代理SERVICESSINCE他們用于動(dòng)態(tài)可擴(kuò)展性，他們可能會(huì)用在一個(gè)插件，風(fēng)格獨(dú)特，配套設(shè)施，如搜索發(fā)動(dòng)和半定制APPLICATIONSSERVLETS還提供強(qiáng)大的平臺(tái)，為半定制應(yīng)用，如基于WEB的訂單輸入或存貨系統(tǒng)。盡管所有的SERVLET是寫在JAVA中，其顧客可以用書面任何LANGUAGEWHENSERVLET是正用在中間層的分布式應(yīng)用系統(tǒng)，他們可以變成客戶其他服務(wù)，寫在任何LANGUAGEFOREXAMPLESERVLETS可以使用JDBC技術(shù)聯(lián)系的一個(gè)應(yīng)用程序的高度調(diào)諧關(guān)系型數(shù)據(jù)庫。溝通與其他種電流或遺留系統(tǒng)?？赡芤愃朴谝蠛蜓a(bǔ)套裝軟件所要求的那樣，這些制度。許多方法使用SERVLET是僅僅是眾多申請(qǐng)的SERVLET是包括一個(gè)簡單的SERVLET處理數(shù)據(jù)被張貼在HTTPS的使用HTML表單中，及其他數(shù)據(jù)，如采購訂單（以信用卡數(shù)據(jù)），這將是一個(gè)組成部分，為了進(jìn)入和處理系統(tǒng)的工作，并一直與產(chǎn)品和庫存數(shù)據(jù)庫，并可能設(shè)立一個(gè)網(wǎng)上支付制度。由于SERVLET是處理多個(gè)請(qǐng)求同時(shí)，要求能同步相互其他支持協(xié)同應(yīng)用，例如網(wǎng)上會(huì)議等功能。人們可以界定一個(gè)社會(huì)的積極推動(dòng)者，分享工作中，每個(gè)OTHERTHE代碼每位代理商將被加載作為一個(gè)SERVLET，以及代理商將通過數(shù)據(jù)向?qū)Ψ絽R報(bào)。一個(gè)SERVLET的，可以提出要求其他SERVERSTHIS技術(shù)，可以平衡負(fù)載中的幾個(gè)服務(wù)器，其中一面鏡子，同時(shí)CONTENTOR，它可以用來分割一個(gè)單一的邏輯服務(wù)幾間服務(wù)器，路由請(qǐng)求，根據(jù)任務(wù)類型或組織界限。該JAVASERVLET的含義是一個(gè)標(biāo)準(zhǔn)的JAVA擴(kuò)展APITHIS意味著，雖然它不是核心的一部分JAVA的框架必須始終一部分，所有產(chǎn)品都以JAVA名稱的，它會(huì)作出一些支持提供這類產(chǎn)品，由他們將這些廠商作為一個(gè)新增功能封裝。SUN公司提供了一套可用于嵌入SERVLET的支持，在其他網(wǎng)站的服務(wù)器，包括阿帕奇（和衍生的服務(wù)器，如為支點(diǎn)）。網(wǎng)景公司FASTTRACK和企業(yè)級(jí)服務(wù)器，并微軟的IIS。SERVLET是最初支持在JAVA的WEBSERVERFROMSUNSINCE則外，其他一些以JAVA為基礎(chǔ)的網(wǎng)絡(luò)服務(wù)器都支持該API的，或者承諾支持它特色的JAVASERVLET規(guī)則。在SERVLETAPI已經(jīng)SUPPODED大多數(shù)基于JAVA的WEB伺服器，并IMPLEMENTALIONS是可用于其他流行的WEBSERVERSTHIS意味著你會(huì)得到JAVA的優(yōu)勢，當(dāng)你使用在SERVLETAPI不僅將你的代碼不會(huì)有內(nèi)存泄露，并受到從硬到找到蠕蟲。您不必鎖定自己成為一個(gè)單一廠商的服務(wù)器擴(kuò)展的API，使用容易出錯(cuò)的語言。如C或腳本LANGUAGESINSTEAD，你可以做你的全部服務(wù)器（和客戶端）的發(fā)展，在單一的開發(fā)LANGUAGEN請(qǐng)問你的團(tuán)隊(duì)必須兼顧多種語文，并配合與可維護(hù)性固有的問題，在腳本LANGUAGESNO不再做你的基于WEB應(yīng)用需要忍受性能和可攜性CGIJAVA是專業(yè)編程工具，你需要提供強(qiáng)有力的伺服器解決方案。根據(jù)該條的規(guī)定，你概括了主要的功能，JAVA的SERVLET是，解決這些問題的主要議題SERVLET的樣子SERVLET的生命周期安全功能HTML是SERVLET的頁面HTTP的特定對(duì)象是SERVLET性能特點(diǎn)SERVLET是什么SERVLET是支持熟悉的編程模型的接受要求，并生成RESPONSESTHIS模型是用各種各樣的分布式系統(tǒng)編程工具，從遠(yuǎn)程過程打電話給HTTP請(qǐng)求作出WEB服務(wù)器。SERVLET是貫徹落實(shí)SERVLET的接口，通常是通過擴(kuò)大無論是通用或一個(gè)HTTP特定IMPLEMENTATIONTHE最簡單可行的SERVLET定義了一個(gè)方法，服務(wù)服務(wù)方法是提供與要求，并響應(yīng)PARAMETERSTHESE概括數(shù)據(jù)派出由客戶提供了機(jī)會(huì)，參數(shù)，并允許SERVLET是為了REPOD地位，其中包括錯(cuò)誤SERVLET是一般取回他們的大部分參數(shù)，通過輸入流，并發(fā)送他們的反應(yīng)的輸出流這些輸入和輸出流，可用于與DATAN什么格式是APPROPRIATEFOR例子一個(gè)APPLET與服務(wù)，可能交換數(shù)據(jù)使用對(duì)象序列化HTML及許多形象格式，也可適當(dāng)?shù)臄?shù)據(jù)格式。SERVLET和環(huán)境狀況由于SERVLET是是JAVA對(duì)象，他們有舉例具體DATATHIS也就是說，在效果SERVLET是正獨(dú)立運(yùn)行的應(yīng)用程序內(nèi)部的服務(wù)器，而無需使用復(fù)雜性增加的班級(jí)。（這是需要一些替代服務(wù)器延伸對(duì)SERVLET的使用）SERVLET是已進(jìn)入某些SERVLET的具體配置數(shù)據(jù)，在初始化TIMETHIS允許不同的事例，同時(shí)SERVLET的級(jí)別被初始化不同的數(shù)據(jù)，并加以管理不同名稱SERVLETSTHE提供的數(shù)據(jù)，在初始化的時(shí)候?qū)ㄒ粋€(gè)領(lǐng)域，每個(gè)舉例來說，將保持其持久性，例如特定STATESERVLETS也有能力進(jìn)行互動(dòng)他們的環(huán)境，通過SERVLETCONTEXT中的物體。SERVLET是已進(jìn)入某些SERVLET的具體配置數(shù)據(jù)，在初始化TIMETHIS允許不同的事例，同時(shí)SERVLET的班級(jí)被初始化不同的數(shù)據(jù)，并加以管理不同名稱SERVLETSTHE提供的數(shù)據(jù)，在初始化的時(shí)候?qū)ㄒ粋€(gè)領(lǐng)域，每個(gè)舉例來說，將保持其持久性，例如特定STATESERVLETS也有能力進(jìn)行互動(dòng)他們的環(huán)境，通過SERVLETCONTEXT中的的語句。什么是SERVLET服務(wù)器也各有不同，他們?nèi)绾沃朗裁磿r(shí)候負(fù)荷SERVLETSWHEN請(qǐng)求進(jìn)來時(shí)，服務(wù)器知道如何繪制它以一個(gè)SERVLET，它可能必須先予以LOADEDTHAT映射通常會(huì)做一取消，這些常見的方式服務(wù)器管理員可以指定一些類型的客戶的要求，始終地圖某一SERVLETFOR舉一個(gè)例子，其中會(huì)談到一個(gè)特定的數(shù)據(jù)庫。服務(wù)器管理員可能會(huì)指明這部分的客戶的要求是名字的SERVLETAS發(fā)現(xiàn)一個(gè)經(jīng)管SERVLET是DIRECTORYAT許多網(wǎng)站，該目錄將分擔(dān)服務(wù)器分擔(dān)負(fù)載的處理，為現(xiàn)場的客戶。有些伺服器或許能夠自動(dòng)調(diào)用SERVLET是過濾輸出的其他SERVLET是根據(jù)他們的行政CONFIGURATIONFOR例如，特定類型的SERVLET的產(chǎn)量就可能觸發(fā)后處理，由其他SERVLET是，或許履行格式轉(zhuǎn)換。適當(dāng)授權(quán)客戶可指定的SERVLET是被引用過，在沒有行政干預(yù)。防偽特征SERVLELS有機(jī)會(huì)獲得信息約其CLIENTSWHEN使用安全協(xié)議，如SSL了。同行的身份可以判定RELIABLYSERVLETS依靠HTTP的，也有進(jìn)入的HTTP特定認(rèn)證數(shù)據(jù)。SERVLET是有JAVA的優(yōu)勢記憶體存取行為，并有強(qiáng)烈的延續(xù)行為。錯(cuò)誤的SERVLET是不會(huì)雕刻的手法是，在大部分C語言服務(wù)器擴(kuò)建環(huán)境。不同于其它任何當(dāng)前服務(wù)器擴(kuò)展API的JAVASERVLET是提供強(qiáng)有力的安全策略SUPPORTTHIS是因?yàn)樗械腏AVA環(huán)境提供一個(gè)安全限制可以用來控制是否將行動(dòng)，例如網(wǎng)絡(luò)或文件訪問，以PERMITTEDBY默認(rèn)情況下，所有SERVLET是不可信的，并不得執(zhí)行操作，如存取網(wǎng)絡(luò)服務(wù)或本地文件。不過，SERVLET是“建在“服務(wù)器內(nèi)部或SERVLET是已進(jìn)行數(shù)字簽名，因?yàn)樗麄儼训絁AVA進(jìn)程的檔案，可能會(huì)受到信任和給予更多的權(quán)限，由保安MANAGERA數(shù)字簽名就可執(zhí)行代碼表明，該組織的出現(xiàn)就意味“先天不足，加上管理松散它“在一些SENSESUCH簽名，不能夠支持問責(zé)制本身，但他們的確顯示一定程度的保證，將被放置在使用該CODEFOR舉例來說，某一特定簽字，從MIS的組織可能需要的所有守則，這是理所當(dāng)然的一般接觸網(wǎng)絡(luò)服務(wù)在一個(gè)企業(yè)INTRANETTHAT簽名可能只用于守則，這是強(qiáng)烈認(rèn)為，不特別是對(duì)違反安全政策。WEB應(yīng)用的生命周期一個(gè)網(wǎng)絡(luò)應(yīng)用軟件的網(wǎng)頁元件，靜態(tài)資源文件，如影像，并幫手班和圖書館。該WEB容器提供了許多配套服務(wù)，致力提升能力的網(wǎng)絡(luò)組件，使它們更容易DEVELOPHOWEVER，因?yàn)橐粋€(gè)WEB應(yīng)用程序必須考慮這些服務(wù)到，這一過程，為創(chuàng)建和運(yùn)行WEB應(yīng)用是不同的是傳統(tǒng)的獨(dú)立的JAVACLASSESTHE過程中，用于創(chuàng)建，部署和執(zhí)行一個(gè)網(wǎng)站應(yīng)用可歸納如下1發(fā)展了WEB組件代碼。2擴(kuò)展了WEB應(yīng)用部署描述符。3編譯WEB應(yīng)用組件和HELPER類參照由組件四可選包申請(qǐng)成為伸展單元，5擴(kuò)展并應(yīng)用到WEB容器6獲得一個(gè)URL，提及WEB應(yīng)用網(wǎng)絡(luò)模塊在JAVAEE的架構(gòu)，WEB組件和靜態(tài)網(wǎng)頁內(nèi)容的文件，如圖像稱為WEB的資源。一個(gè)網(wǎng)絡(luò)模塊是最小的部署和使用單位的網(wǎng)站RESOURCESAJAVAEE的網(wǎng)站單元對(duì)應(yīng)一個(gè)WEB應(yīng)用作為定義在JAVASERVLET的規(guī)范。此外，以WEB組件和網(wǎng)絡(luò)資源，網(wǎng)絡(luò)模塊可包含其他文件。服務(wù)器端實(shí)用班（數(shù)據(jù)庫類等）。通常，這些符合需要J