jsp技术概述与应用框架外文翻译.doc

jsp技术概述与应用框架外文翻译.doc

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外文原文

OverviewofJSPTechnologyandJSPapplicationframeworks

Autor:

ZambonGiulio/SeklerMichael

Source:

Springer-VerlagNewYorkInc

1．BenefitsofJSP

JSPpagesaretranslatedintoservlets.So,fundamentally,anytaskJSPpagescanperformcouldalsobeaccomplishedbyservlets.However,thisunderlyingequivalencedoesnotmeanthatservletsandJSPpagesareequallyappropriateinallscenarios.Theissueisnotthepowerofthetechnology,itistheconvenience,productivity,andmaintainabilityofoneortheother.Afterall,anythingyoucandoonaparticularcomputerplatformintheJavaprogramminglanguageyoucouldalsodoinassemblylanguage.Butitstillmatterswhichyouchoose.JSPprovidesthefollowingbenefitsoverservletsalone:

•ItiseasiertowriteandmaintaintheHTML.YourstaticcodeisordinaryHTML:

noextrabackslashes,nodoublequotes,andnolurkingJavasyntax.

•YoucanusestandardWeb-sitedevelopmenttools.EvenHTMLtoolsthatknownothingaboutJSPcanbeusedbecausetheysimplyignoretheJSPtags.

•Youcandivideupyourdevelopmentteam.TheJavaprogrammerscanworkonthedynamiccode.TheWebdeveloperscanconcentrateonthepresentationlayer.Onlargeprojects,thisdivisionisveryimportant.Dependingonthesizeofyourteamandthecomplexityofyourproject,youcanenforceaweakerorstrongerseparationbetweenthestaticHTMLandthedynamiccontent.

Now,thisdiscussionisnottosaythatyoushouldstopusingservletsanduseonlyJSPinstead.Bynomeans.Almostallprojectswilluseboth.Forsomerequestsinyourproject,youwilluseservlets.Forothers,youwilluseJSP.Forstillothers,youwillcombinethemwiththeMVCarchitecture.Youwanttheappropriatetoolforthejob,andservlets,bythemselves,donotcompleteyourtoolkit.

2.AdvantagesofJSPOverCompetingTechnologies

Anumberofyearsago,Martywasinvitedtoattendasmall20-personindustryroundtablediscussiononsoftwaretechnology.SittingintheseatnexttoMartywasJamesGosling,inventoroftheJavaprogramminglanguage.Sittingseveralseatsawaywasahigh-levelmanagerfromaverylargesoftwarecompanyinRedmond,Washington.Duringthediscussion,themoderatorbroughtupthesubjectofJini,whichatthattimewasanewJavatechnology.Themoderatoraskedthemanagerwhathethoughtofit,andthemanagerrespondedthatitwastooearlytotell,butthatitseemedtobeanexcellentidea.Hewentontosaythattheywouldkeepaneyeonit,andifitseemedtobecatchingon,theywouldfollowhiscompany'susual"embraceandextend"strategy.Atthispoint,Goslinglightheartedlyinterjected"Youmeandisgraceanddistend."

Now,thegrievancethatGoslingwasairingwasthathefeltthatthiscompanywouldtaketechnologyfromothercompaniesandsubornitfortheirownpurposes.Butguesswhat?

Theshoeisontheotherfoothere.TheJavacommunitydidnotinventtheideaofdesigningpagesasamixtureofstaticHTMLanddynamiccodemarkedwithspecialtags.Forexample,ColdFusiondidityearsearlier.EvenASP（aproductfromtheverysoftwarecompanyoftheaforementionedmanager）popularizedthisapproachbeforeJSPcamealonganddecidedtojumponthebandwagon.Infact,JSPnotonlyadoptedthegeneralidea,itevenusedmanyofthesamespecialtagsasASPdid..So,thequestionbecomes:

whyuseJSPinsteadofoneoftheseothertechnologies?

Ourfirstresponseisthatwearenotarguingthateveryoneshould.Severalofthoseothertechnologiesarequitegoodandarereasonableoptionsinsomesituations.Inothersituations,however,JSPisclearlybetter.Hereareafewofthereasons.

2.1Versus.NETandActiveServerPages（ASP）

.NETiswell-designedtechnologyfromMicrosoft.ASP.NETisthepartthatdirectlycompeteswithservletsandJSP.TheadvantagesofJSParetwofold.First,JSPisportabletomultipleoperatingsystemsandWebservers;youaren'tlockedintodeployingonWindowsandIIS.Althoughthecore.NETplatformrunsonafewnon-Windowsplatforms,theASPpartdoesnot.YoucannotexpecttodeployseriousASP.NETapplicationsonmultipleserversandoperatingsystems.Forsomeapplications,thisdifferencedoesnotmatter.Forothers,itmattersgreatly.Second,forsomeapplicationsthechoiceoftheunderlyinglanguagemattersgreatly.Forexample,although.NET'sC#languageisverywelldesignedandissimilartoJava,fewerprogrammersarefamiliarwitheitherthecoreC#syntaxorthemanyauxiliarylibraries.Inaddition,manydevelopersstillusetheoriginalversionofASP.Withthisversion,JSPhasaclearadvantageforthedynamiccode.WithJSP,thedynamicpartiswritteninJava,notVBScriptoranotherASP-specificlanguage,soJSPismorepowerfulandbettersuitedtocomplexapplicationsthatrequirereusablecomponents.

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