计算机外文文献及翻译(SSH)

附录AHistoryDuke,theJavamascotJamesGosling,MikeSheridan,andPatrickNaughtoninitiatedtheJavalanguageprojectinJune1991.Javawasoriginallydesignedforinteractivetelevision,butitwastooadvancedforthedigitalcabletelevisionindustryatthetime.ThelanguagewasinitiallycalledOakafteranoaktreethatstoodoutsideGosling'soffice;itwentbythenameGreenlater,andwaslaterrenamedJava,fromalistofrandomwords.GoslingaimedtoimplementavirtualmachineandalanguagethathadafamiliarC/C++styleofnotation.SunMicrosystemsreleasedthefirstpublicimplementationasJava1.0in1995.ItpromisedWriteOnce,RunAnywhere(WORA),providingno-costrun-timesonpopularplatforms.Fairlysecureandfeaturingconfigurablesecurity,itallowednetwork-andfile-accessrestrictions.MajorwebbrowserssoonincorporatedtheabilitytorunJavaappletswithinwebpages,andJavaquicklybecamepopular.WiththeadventofJava2(releasedinitiallyasJ2SE1.2inDecember1998–1999),newversionshadmultipleconfigurationsbuiltfordifferenttypesofplatforms.Forexample,J2EEtargetedenterpriseapplicationsandthegreatlystripped-downversionJ2MEformobileapplications(MobileJava).J2SEdesignatedtheStandardEdition.In2006,formarketingpurposes,SunrenamednewJ2versionsasJavaEE,JavaME,andJavaSE,respectively.In1997,SunMicrosystemsapproachedtheISO/IECJTC1standardsbodyandlatertheEcmaInternationaltoformalizeJava,butitsoonwithdrewfromtheprocess.Javaremainsadefactostandard,controlledthroughtheJavaCommunityProcess.Atonetime,SunmademostofitsJavaimplementationsavailablewithoutcharge,despitetheirproprietarysoftwarestatus.SungeneratedrevenuefromJavathroughthesellingoflicensesforspecializedproductssuchastheJavaEnterpriseSystem.SundistinguishesbetweenitsSoftwareDevelopmentKit(SDK)andRuntimeEnvironment(JRE)(asubsetoftheSDK);theprimarydistinctioninvolvestheJRE'slackofthecompiler,utilityprograms,andheaderfiles.OnNovember13,2006,SunreleasedmuchofJavaasopensourcesoftwareunderthetermsoftheGNUGeneralPublicLicense(GPL).OnMay8,2007,Sunfinishedtheprocess,makingallofJava'scorecodeavailableunderfreesoftware/open-sourcedistributionterms,asidefromasmallportionofcodetowhichSundidnotholdthecopyright.Sun'svice-presidentRichGreenhassaidthatSun'sidealrolewithregardstoJavaisasanevangelist.FollowingOracleCorporation'sacquisitionofSunMicrosystemsin2009–2010,OraclehasdescribeditselfasthestewardofJavatechnologywitharelentlesscommitmenttofosteringacommunityofparticipationandtransparency.PrinciplesTherewerefiveprimarygoalsinthecreationoftheJavalanguage:1.Itshouldbesimple,objectoriented,andfamiliar、2.Itshouldberobustandsecure.3.Itshouldbearchitectureneutralandportable、4.Itshouldexecutewithhighperformance、5.Itshouldbeinterpreted,threaded,anddynamic.JavaPlatformMainarticles:Java(softwareplatform)andJavaVirtualMachineOnecharacteristicofJavaisportability,whichmeansthatcomputerprogramswrittenintheJavalanguagemustrunsimilarlyonanysupportedhardware/operating-systemplatform.ThisisachievedbycompilingtheJavalanguagecodetoanintermediaterepresentationcalledJavabytecode,insteadofdirectlytoplatform-specificmachinecode.Javabytecodeinstructionsareanalogoustomachinecode,butareintendedtobeinterpretedbyavirtualmachine(VM)writtenspecificallyforthehosthardware.End-userscommonlyuseaJavaRuntimeEnvironment(JRE)installedontheirownmachineforstandaloneJavaapplications,orinaWebbrowserforJavaapplets.Standardizedlibrariesprovideagenericwaytoaccesshost-specificfeaturessuchasgraphics,threading,andnetworking.Amajorbenefitofusingbytecodeisporting.However,theoverheadofinterpretationmeansthatinterpretedprogramsalmostalwaysrunmoreslowlythanprogramscompiledtonativeexecutableswould.Just-in-Timecompilerswereintroducedfromanearlystagethatcompilebytecodestomachinecodeduringruntime.ImplementationsSunMicrosystemsofficiallylicensestheJavaStandardEditionplatformforLinux,MacOSX,andSolaris.AlthoughinthepastSunhaslicensedJavatoMicrosoft,thelicensehasexpiredandhasnotbeenrenewed.Throughanetworkofthird-partyvendorsandlicensees,alternativeJavaenvironmentsareavailablefortheseandotherplatforms.Sun'strademarklicenseforusageoftheJavabrandinsiststhatallimplementationsbecompatible.ThisresultedinalegaldisputewithMicrosoftafterSunclaimedthattheMicrosoftimplementationdidnotsupportRMIorJNIandhadaddedplatform-specificfeaturesoftheirown.Sunsuedin1997,andin2001wonasettlementofUS$20million,aswellasacourtorderenforcingthetermsofthelicensefromSun.Asaresult,MicrosoftnolongershipsJavawithWindows,andinrecentversionsofWindows,InternetExplorercannotsupportJavaappletswithoutathird-partyplugin.Sun,andothers,havemadeavailablefreeJavarun-timesystemsforthoseandotherversionsofWindows.Platform-independentJavaisessentialtotheJavaEEstrategy,andanevenmorerigorousvalidationisrequiredtocertifyanimplementation.Thisenvironmentenablesportableserver-sideapplications,suchasWebservices,JavaServlets,andEnterpriseJavaBeans,aswellaswithembeddedsystemsbasedonOSGi,usingEmbeddedJavaenvironments.ThroughthenewGlassFishproject,Sunisworkingtocreateafullyfunctional,unifiedopensourceimplementationoftheJavaEEtechnologies.SunalsodistributesasupersetoftheJREcalledtheJavaDevelopmentKit(commonlykn