jsp网站开发毕设外文翻译Word下载.docx

jsp网站开发毕设外文翻译Word下载.docx

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院（系）:

计算机学院专业:

计算机科学与技术班级:

学生姓名:

导师姓名:

职称:

起止时间:

2011年9月23日至2012年6月2日

原文:

JavaandtheInternet

AlthoughJavaisveryusefulforsolvingtraditionalstand-aloneprogrammingproblems,itisalsoimportantbecauseitwillsolveprogrammingproblemsontheWorldWideWeb.

1.Client-sideprogramming

TheWeb’sinitialserver-browserdesignprovidedforinteractivecontent,buttheinteractivitywascompletelyprovidedbytheserver.Theserverproducedstaticpagesfortheclientbrowser,whichwouldsimplyinterpretanddisplaythem.BasicHTMLcontainssimplemechanismsfordatagathering:

text-entryboxes,checkboxes,radioboxes,listsanddrop-downlists,aswellasabuttonthatcanonlybeprogrammedtoresetthedataontheformor“submit”thedataontheformbacktotheserver.ThissubmissionpassesthroughtheCommonGatewayInterface（CGI）providedonallWebservers.ThetextwithinthesubmissiontellsCGIwhattodowithit.Themostcommonactionistorunaprogramlocatedontheserverinadirectorythat’stypicallycalled“cgi-bin.”（Ifyouwatchtheaddresswindowatthetop

ofyourbrowserwhenyoupushabuttononaWebpage,youcansometimessee“cgi-bin”withinallthe

gobbledygookthere.）Theseprogramscanbewritteninmostlanguages.Perlisacommonchoicebecauseitisdesignedfortextmanipulationandisinterpreted,soitcanbeinstalledonanyserverregardlessofprocessororoperatingsystem.

ManypowerfulWebsitestodayarebuiltstrictlyonCGI,andyoucaninfactdonearlyanythingwithit.However,WebsitesbuiltonCGIprogramscanrapidlybecomeoverlycomplicatedtomaintain,andthereisalsotheproblemofresponsetime.TheresponseofaCGIprogramdependsonhowmuchdatamustbesent,aswellastheloadonboththeserverandtheInternet.（Ontopofthis,startingaCGIprogramtendstobeslow.）TheinitialdesignersoftheWebdidnotforeseehowrapidlythisbandwidthwouldbeexhaustedforthekindsofapplicationspeopledeveloped.Forexample,anysortofdynamicgraphingisnearlyimpossibletoperformwithconsistencybecauseaGIFfilemustbecreatedandmovedfromtheservertotheclientforeachversionofthegraph.Andyou’venodoubthaddirectexperiencewithsomethingassimpleasvalidatingthedataonaninputform.Youpressthesubmitbuttononapage;

thedataisshippedbacktotheserver;

theserverstartsaCGIprogramthatdiscoversanerror,formatsanHTMLpageinformingyouoftheerror,andthensendsthepagebacktoyou;

youmustthenbackupapageandtryagain.Notonlyisthisslow,it’sinelegant.

Thesolutionisclient-sideprogramming.MostmachinesthatrunWebbrowsersarepowerfulenginescapableofdoingvastwork,andwiththeoriginalstaticHTMLapproachtheyaresittingthere,justidlywaitingfortheservertodishupthenextpage.Client-sideprogrammingmeansthattheWebbrowserisharnessedtodowhateverworkitcan,andtheresultfortheuserisamuchspeedierandmoreinteractive

experienceatyourWebsite.

Theproblemwithdiscussionsofclient-sideprogrammingisthattheyaren’tverydifferentfrom

discussionsofprogrammingingeneral.Theparametersarealmostthesame,buttheplatformisdifferent:

aWebbrowserislikealimitedoperatingsystem.Intheend,youmuststillprogram,andthisaccountsforthedizzyingarrayofproblemsandsolutionsproducedbyclient-sideprogramming.Therestofthissectionprovidesanoverviewoftheissuesandapproachesinclient-sideprogramming.2.Plug-ins

Oneofthemostsignificantstepsforwardinclient-sideprogrammingisthedevelopmentoftheplug-in.Thisisawayforaprogrammertoaddnewfunctionalitytothebrowserbydownloadingapieceofcodethatplugsitselfintotheappropriatespotinthebrowser.Ittellsthebrowser“fromnowonyoucanperformthisnewactivity.”（Youneedtodownloadtheplug-inonlyonce.）Somefastandpowerful

behaviorisaddedtobrowsersviaplug-ins,butwritingaplug-inisnotatrivialtask,andisn’tsomething

you’dwanttodoaspartoftheprocessofbuildingaparticularsite.Thevalueoftheplug-infor

client-sideprogrammingisthatitallowsanexpertprogrammertodevelopanewlanguageandaddthatlanguagetoabrowserwithoutthepermissionofthebrowsermanufacturer.Thus,plug-insprovidea“backdoor”thatallowsthecreationofnewclient-sideprogramminglanguages（althoughnotall

languagesareimplementedasplug-ins）.

3.Scriptinglanguages

Plug-insresultedinanexplosionofscriptinglanguages.Withascriptinglanguageyouembedthesourcecodeforyourclient-sideprogramdirectlyintotheHTMLpage,andtheplug-inthatinterpretsthatlanguageisautomaticallyactivatedwhiletheHTMLpageisbeingdisplayed.Scriptinglanguagestendtobereasonablyeasytounderstandand,