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1、附录一外文资料原文：ABOUTJAVATECHNOLOGYServletsandJSP:AnOverview1.WhatareJavaServlets?ServletsareJavatechnology'sanswertoCGIprogramming.TheyareprogramsthatrunonaWebserverandbuildWebpages.BuildingWebpagesontheflyisuseful(andcommonlydone)foranumberofreasons:·TheWebpageisbasedondatasubmittedby
2、theuser.Forexampletheresultspagesfromsearchenginesaregeneratedthisway,andprogramsthatprocessordersfore-commercesitesdothisaswell.·Thedatachangesfrequently.Forexample,aweather-reportornewsheadlinespagemightbuildthepagedynamically,perhapsreturningapreviouslybuiltpageifitisstilluptod
3、ate.·TheWebpageusesinformationfromcorporatedatabasesorothersuchsources.Forexample,youwouldusethisformakingaWebpageatanon-linestorethatlistscurrentpricesandnumberofitemsinstock.2.WhataretheAdvantageofServletsOver"Traditional"CGI?Javaservletsaremoreefficient,easiertouse,morepowerful
4、,moreportable,andcheaperthantraditionalCGIandthanmanyalternativeCGI-liketechnologies.(Moreimportantly,servletdevelopersgetpaidmorethanPerlprogrammers:-).·Efficient.WithtraditionalCGI,anewprocessisstartedforeachHTTPrequest.IftheCGIprogramdoesarelativelyfastoperation,theoverheadofst
5、artingtheprocesscandominatetheexecutiontime.Withservlets,theJavaVirtualMachinestaysup,andeachrequestishandledbyalightweightJavathread,notaheavyweightoperatingsystemprocess.Similarly,intraditionalCGI,ifthereareNsimultaneousrequesttothesameCGIprogram,thenthecodefortheCGIprogramisloa
6、dedintomemoryNtimes.Withservlets,however,thereareNthreadsbutonlyasinglecopyoftheservletclass.ServletsalsohavemorealternativesthandoregularCGIprogramsforoptimizationssuchascachingpreviouscomputations,keepingdatabaseconnectionsopen,andthelike.·Convenient.Hey,youalreadyknowJava.Whyle
7、arnPerltoo?Besidestheconvenienceofbeingabletouseafamiliarlanguage,servletshaveanextensiveinfrastructureforautomaticallyparsinganddecodingHTMLformdata,readingandsettingHTTPheaders,handlingcookies,trackingsessions,andmanyothersuchutilities.·Powerful.Javaservletsletyoueasilydoseveral
8、thingsthataredifficultorimpossibl
