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1、JavaandtheInternetIfJavais,infact,yetanothercomputerprogramminglanguage,youmayquestionwhyitissoimportantandwhyitisbeingpromotedasarevolutionarystepincomputerprogramming.Theanswerisn’timmediatelyobviousifyou’recomingfromatraditionalprogrammingperspective.AlthoughJavaisveryusefulforsolvi
2、ngtraditionalstand-aloneprogrammingproblems,itisalsoimportantbecauseitwillsolveprogrammingproblemsontheWorldWideWeb.1.Client-sideprogrammingTheWeb’sinitialserver-browserdesignprovidedforinteractivecontent,buttheinteractivitywascompletelyprovidedbytheserver.Theserverproducedstaticpagesf
3、ortheclientbrowser,whichwouldsimplyinterpretanddisplaythem.BasicHTMLcontainssimplemechanismsfordatagathering:text-entryboxes,checkboxes,radioboxes,listsanddrop-downlists,aswellasabuttonthatcanonlybeprogrammedtoresetthedataontheformor“submit”thedataontheformbacktotheserver.Thissubmissio
4、npassesthroughtheCommonGatewayInterface(CGI)providedonallWebservers.ThetextwithinthesubmissiontellsCGIwhattodowithit.Themostcommonactionistorunaprogramlocatedontheserverinadirectorythat’stypicallycalled“cgi-bin.”(IfyouwatchtheaddresswindowatthetopofyourbrowserwhenyoupushabuttononaWebpa
5、ge,youcansometimessee“cgi-bin”withinallthegobbledygookthere.)Theseprogramscanbewritteninmostlanguages.Perlisacommonchoicebecauseitisdesignedfortextmanipulationandisinterpreted,soitcanbeinstalledonanyserverregardlessofprocessororoperatingsystem.ManypowerfulWebsitestodayarebuiltstrictlyo
6、nCGI,andyoucaninfactdonearlyanythingwithit.However,WebsitesbuiltonCGIprogramscanrapidlybecomeoverlycomplicatedtomaintain,andthereisalsotheproblemofresponsetime.TheresponseofaCGIprogramdependsonhowmuchdatamust18besent,aswellastheloadonboththeserverandtheInternet.(Ontopofthis,startingaCG
7、Iprogramtendstobeslow.)TheinitialdesignersoftheWebdidnotforeseehowrapidlythisbandwidthwouldbeexhaustedforthekindsofapplicationspeopledeveloped.Forexample,anysortofdynamicgraphingisnearlyimpossibletoperformwithconsistencybecauseaGIFfilemustbecreatedandmovedfromtheservertotheclientfore
