JSP外文文献原稿和译.docx
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JSP外文文献原稿和译.docx
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JSP外文文献原稿和译
外文文献原稿和译文
原稿
JSP
JSP(JavaServerPages)isinitiatedbySunMicrosystems,Inc.,withmanycompaniestoparticipateintheestablishmentofadynamicwebpagetechnicalstandards.JSPtechnologysomewhatsimilartoASPtechnology,itisinthetraditionalHTMLwebpagedocument(*.htm,*.html)toinserttheJavaprogrammingparagraph(Scriptlet)andJSPtag(tag),thusJSPdocuments(*.jsp).
UsingJSPdevelopmentoftheWebapplicationiscross-platformthatcanrunonLinux,isalsoavailableforotheroperatingsystems.
JSPtechnologytousetheJavaprogramminglanguagepreparedbythecategoryofXMLtagsandscriptlets,toproducedynamicpagespackageprocessinglogic.Pagealsovisitby tagsandscriptletsexistintheservicessideoftheresourcesoflogic.JSPpagelogicandwebpagedesignanddisplayseparation,supportreusablecomponent-baseddesign,Web-basedapplicationdevelopmentisrapidandeasy.
WebserverinthefaceofvisitsJSPpagerequest,thefirstimplementationoftheproceduresof,andthentogetherwiththeresultsoftheimplementationofJSPdocumentsinHTMLcodewiththereturntothecustomer.InserttheJavaprogrammingoperationofthedatabasecanbere-orientedwebsites,inordertoachievetheestablishmentofdynamicpagesneededtofunction.
JSPandJavaServlet,isintheimplementationoftheserver,usuallyreturnedtotheclientisanHTMLtext,aslongastheclientbrowserwillbeabletovisit.
JSPpagesfromHTMLcodeandJavacodeembeddedinoneofthecomponents.TheserverwasinthepagesofclientrequestsaftertheJavacodeandthenwillgeneratetheHTMLpagestoreturntotheclientbrowser.JavaServletJSPisthetechnicalfoundationandlarge-scaleWebapplicationdevelopmentneedsofJavaServletandJSPsupporttocomplete.JSPwiththeJavatechnologyeasytouse,fullyobject-oriented,andaplatform-independentandsecure,mainlyforallthecharacteristicsoftheInternet.
JavaScript,whichiscompletelydistinctfromtheJavaprogramminglanguage,isnormallyusedtodynamicallygenerateHTMLontheclient,buildingpartsoftheWebpageasthebrowserloadsthedocument.ThisisausefulcapabilityanddoesnotnormallyoverlapwiththecapabilitiesofJSP(whichrunsonlyontheserver).JSPpagesstillincludeSCRIPTtagsforJavaScript,justasnormalHTMLpagesdo.Infact,JSPcanevenbeusedtodynamicallygeneratetheJavaScriptthatwillbesenttotheclient.So,JavaScriptisnotacompetingtechnology;itisacomplementaryone.ItisalsopossibletouseJavaScriptontheserver,mostnotablyonSunONE(formerlyiPlanet),IIS,andBroadVisionservers.However,Javaismorepowerful,flexible,reliable,andportable.
JSP(arecursiveacronymfor"JSP:
HypertextPreprocessor")isafree,open-source,HTML-embeddedscriptinglanguagethatissomewhatsimilartobothASPandJSP.OneadvantageofJSPisthatthedynamicpartiswritteninJava,whichalreadyhasanextensiveAPIfornetworking,databaseaccess,distributedobjects,andthelike,whereasPHPrequireslearninganentirelynew,lesswidelyusedlanguage.AsecondadvantageisthatJSPismuchmorewidelysupportedbytoolandservervendorsthanisJSP.VersusPureServlets.
JSPdoesn'tprovideanycapabilitiesthatcouldn't,inprinciple,beaccomplishedwithservlets.Infact,JSPdocumentsareautomaticallytranslatedintoservletsbehindthescenes.Butitismoreconvenienttowrite(andtomodify!
)regularHTMLthantouseazillionprintlnstatementstogeneratetheHTML.Plus,byseparatingthepresentationfromthecontent,youcanputdifferentpeopleondifferenttasks:
yourWebpagedesignexpertscanbuildtheHTMLbyusingfamiliartoolsandeitherleaveplacesforyourservletprogrammerstoinsertthedynamiccontentorinvokethedynamiccontentindirectlybymeansofXMLtags.
JSPtechnologystrength
(1) timetoprepare,runeverywhere.AtthispointJavabetterthanPHP,inadditiontosystems,thecodenottomakeanychanges.
(2) themulti-platformsupport.Basicallyonallplatformsofanydevelopmentenvironment,inanyenvironmentfordeploymentinanyenvironmentintheexpansion.ComparedASP/PHPlimitationsareobvious.
(3) astrongscalability.FromonlyasmallJardocumentscanrunServletJSP,tothemultipleserversclusteringandloadbalancing,tomultipleApplicationfortransactionprocessing,informationprocessing,aservertonumerousservers,JavashowsatremendousVitality.
(4) diversificationandpowerfuldevelopmenttoolssupport.ThisissimilartotheASP,Javaalreadyhavemanyverygooddevelopmenttools,andmanycanbefree,andmanyofthemhavebeenabletorunonavarietyofplatformsunder.
JSPtechnologyvulnerable:
(1) andthesameASP,Javaistheadvantageofsomeofitsfatalproblem.Itispreciselybecauseinordertocross-platformfunctionality,inordertoextremestretchingcapacity,greatlyincreasingthecomplexityoftheproduct.
(2) Java'sspeedisclasstocompletethepermanentmemory,soinsomecasesbytheuseofmemorycomparedtothenumberofusersisindeeda"minimumcostperformance."Ontheotherhand,italsoneedsdiskspacetostoreaseriesof.Javadocumentsand.Class,aswellasthecorrespondingversionsofdocuments.
Knowservletsforfourreasons:
1. JSPpagesgettranslatedintoservlets.Youcan'tunderstandhowJSPworkswithoutunderstandingservlets.
2. JSPconsistsofstaticHTML,special-purposeJSPtags,andJavacode.WhatkindofJavacode?
Servletcode!
Youcan'twritethatcodeifyoudon'tunderstandservletprogramming.
3. SometasksarebetteraccomplishedbyservletsthanbyJSP.JSPisgoodatgeneratingpagesthatconsistoflargesectionsoffairlywellstructuredHTMLorothercharacterdata.Servletsarebetterforgeneratingbinarydata,buildingpageswithhighlyvariablestructure,andperformingtasks(suchasredirection)thatinvolvelittleornooutput.
4. SometasksarebetteraccomplishedbyacombinationofservletsandJSPthanbyeitherservletsorJSPalone.
VersusJavaScript
JavaScript,whichiscompletelydistinctfromtheJavaprogramminglanguage,isnormallyusedtodynamicallygenerateHTMLontheclient,buildingpartsoftheWebpageasthebrowserloadsthedocument.ThisisausefulcapabilityanddoesnotnormallyoverlapwiththecapabilitiesofJSP(whichrunsonlyontheserver).JSPpagesstillincludeSCRIPTtagsforJavaScript,justasnormalHTMLpagesdo.Infact,JSPcanevenbeusedtodynamicallygeneratetheJavaScriptthatwillbesenttotheclient.So,JavaScriptisnotacompetingtechnology;itisacomplementaryone.
JSPisbynomeansperfect.Manypeoplehavepointedoutfeaturesthatcouldbeimproved.Thisisagoodthing,andoneoftheadvantagesofJSPisthatthespecificationiscontrolledbyacommunitythatdrawsfrommanydifferentcompanies.So,thetechnologycanincorporateimprovementsinsuccessivereleases.
However,somegroupshavedevelopedalternativeJava-basedtechnologiestotrytoaddressthesedeficiencies.This,inourjudgment,isamistake.Usingathird-partytoollikeApacheStrutsthataugmentsJSPandservlettechnologyisagoodideawhenthattooladdssufficientbenefittocompensatefortheadditionalcomplexity.ButusinganonstandardtoolthattriestoreplaceJSPisabadidea.Whenchoosingatechnology,youneedtoweighmanyfactors:
standardization,portability,integration,industrysupport,andtechnicalfeatures.TheargumentsforJSPalternativeshavefocusedalmostexclusivelyonthetechnicalfeaturespart.Butportability,standardization,andintegrationarealsoveryimportant.Forexample,theservletandJSPspecificationsdefineastandarddirectorystructureforWebapplicationsandprovidestandardfiles(.warfiles)fordeployingWebapplications.AllJSP-compatibleserversmustsupportthesestandards.FilterscanbesetuptoapplytoanynumberofservletsorJSPpages,butnottononstandardresources.ThesamegoesforWebapplicationsecuritysettings.
JSPsixbuilt-inobjects:
request,response,out,session,application,config,pagecontext,page,exception.
ONE. Requestfor:
Theobjectofthepackageofinformationsubmittedbyusers,bycallingtheobjectcorrespondingwaytoaccesstheinformationpackage,namelytheuseofthetargetuserscanaccesstheinformation.
TWO. Responseobject:
Thecustomer'srequestdynamicresponsetotheclientsentthedata.
THREE. sessionobject
1. Whatisthesession:
sessionobjectisabuilt-inobjectsJSP,itinthefirstJSPpagesloadedautomaticallycreate,completetheconversationofmanagement.
Fromacustomertoopenabrowserandconnecttotheserver,toclosethebrowser,leavingtheendofthisserver,knownasaconversation.Whenacustomervisitsaserver,theservermaybeafewpageslinkbetweenrepeatedly,repeatedlyrefreshapage,theservershouldbethroughsomekindofwaytoknowthisisthesameclient,whichrequiressessionobject.
2. sessionobjectID:
Whenacustomer'sfirstvisittoaserverontheJSPpages,JSPenginesproduceasessionobject,andassignedaStringtypeofIDnumber,JSPengineatthesametime,theIDnumbersenttotheclient,storedinCookie,thissessionobjects,andcustomersontheestablishmentofaone-to-onerelationship.Whenacustomertoconnecttotheserveroftheotherpages,customersnolongerallocatedtothenewsessionobject,until,closeyourbrowser,theclient-serverobjecttocancelthesession,andtheconversation,andcustomerrelationshipdisappeared.Whenacustomerre-openthebrowsertoconnecttotheserver,theserverforthecustomertocreateanewsessionobject.
FORE. aplicationtarget
1. Whatistheapplication:
Servershavelaunch
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