资源描述：
《servlet和jsp技术简述(英文翻译)》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。
1、AnOverviewofServletandJSPTechnologyGildasAvoineandPhilippeOechslinEPFL,Lausanne,Switzerland1.1AServlet'sJobServletsareJavaprogramsthatrunonWeborapplicationservers,actingasamiddlelayerbetweenrequestscomingfromWebbrowsersorotherHTTPclientsanddatabasesorapplicationsontheHTTPs
2、erver.Theirjobistoperformthefollowingtasks,asillustratedinFigure1-1.Figure1-11．Readtheexplicitdatasentbytheclient.TheendusernormallyentersthisdatainanHTMLformonaWebpage.However,thedatacouldalsocomefromanappletoracustomHTTPclientprogram.2．ReadtheimplicitHTTPrequestdatasentb
3、ythebrowser.Figure1-1showsasinglearrowgoingfromtheclienttotheWebserver(thelayerwhereservletsandJSPexecute),buttherearereallytwovarietiesofdata:theexplicitdatathattheenduserentersinaformandthebehind-the-scenesHTTPinformation.Bothvarietiesarecritical.TheHTTPinformationinclud
4、escookies,informationaboutmediatypesandcompressionschemesthebrowserunderstands,andsoon.3．Generatetheresults.Thisprocessmayrequiretalkingtoadatabase,executinganRMIorEJBcall,invokingaWebservice,orcomputingtheresponsedirectly.Yourrealdatamaybeinarelationaldatabase.Fine.Butyou
5、rdatabaseprobablydoesn'tspeakHTTPorreturnresultsinHTML,sotheWebbrowsercan'ttalkdirectlytothedatabase.Evenifitcould,forsecurityreasons,youprobablywouldnotwantitto.Thesameargumentappliestomostotherapplications.YouneedtheWebmiddlelayertoextracttheincomingdatafromtheHTTPstream
6、,talktotheapplication,andembedtheresultsinsideadocument.4．Sendtheexplicitdata(i.e.,thedocument)totheclient.Thisdocumentcanbesentinavarietyofformats,includingtext(HTMLorXML),binary(GIFimages),orevenacompressedformatlikegzipthatislayeredontopofsomeotherunderlyingformat.But,H
7、TMLisbyfarthemostcommonformat,soanimportantservlet/JSPtaskistowraptheresultsinsideofHTML.5．SendtheimplicitHTTPresponsedata.Figure1-1showsasinglearrowgoingfromtheWebmiddlelayer(theservletorJSPpage)totheclient.But,therearereallytwovarietiesofdatasent:thedocumentitselfandtheb
8、ehind-the-scenesHTTPinformation.Again,bothvarietiesarecriticaltoeffectivedevelopment.Send
