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1、Servlet和JSP技术简介中英文资料外文翻译文献AnOverviewofServletandJSPTechnologyMartyHallandLarryBrown，2000-07,CoreServletsandJavaServerPageschapter11.1AServlet'sJobServletsareJavaprogramsthatrunonWeborapplicationservers,actingasamiddlelayerbetweenrequestscomingfromWebbrowsersorotherHTTPclientsanddatabasesorapplicat
2、ionsontheHTTPserver.Theirjobistoperformthefollowingtasks,asillustratedinFigure1-1.Figure1-11．Readtheexplicitdatasentbytheclient.TheendusernormallyentersthisdatainanHTMLformonaWebpage.However,thedatacouldalsocomefromanappletoracustomHTTPclientprogram.2．ReadtheimplicitHTTPrequestdatasentbythebrowser
3、.Figure1-1showsasinglearrowgoingfromtheclienttotheWebserver(thelayerwhereservletsandJSPexecute),buttherearereallytwovarietiesofdata:theexplicitdatathattheenduserentersinaformandthebehind-the-scenesHTTPinformation.Bothvarietiesarecritical.TheHTTPinformationincludescookies,informationaboutmediatypes
4、andcompressionschemesthebrowserunderstands,andsoon.3．Generatetheresults.Thisprocessmayrequiretalkingtoadatabase,executinganRMIorEJBcall,invokingaWebservice,orcomputingtheresponsedirectly.Yourrealdatamaybeinarelationaldatabase.Fine.Butyourdatabaseprobablydoesn'tspeakHTTPorreturnresultsinHTML,sotheW
5、ebbrowsercan'ttalkdirectlytothedatabase.Evenifitcould,forsecurityreasons,youprobablywouldnotwantitto.Thesameargumentappliestomostotherapplications.YouneedtheWebmiddlelayertoextracttheresultsinsideadocument.4．Sendtheexplicitdata(i.e.,thedocument)totheclient.Thisdocumentcanbesentinavarietyofformats,
6、includingtext(HTMLorXML),binary(GIFimages),orevenacompressedformatlikegzipthatislayeredontopofsomeotherunderlyingformat.But,HTMLisbyfarthemostcommonformat,soanimportantservlet/JSPtaskistowraptheresultsinsideofHTML.5．SendtheimplicitHTTPresponsedata.Figure1-1showsasinglearrowgoingfromtheWebmiddlelay
7、er(theservletorJSPpage)totheclient.But,therearereallytwovarietiesofdatasent:thedocumentitselfandthebehind-the-scenesHTTPinformation.Again,bothvarietiesarecriticaltoeffectivedevelopment.SendingHTTPresponsedatainvo
