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1、毕业设计说明书CoreJavaJava核心技术软件学院学生姓名：学号：软件工程学院：专业：指导教师：2014年6月CoreJavaWhenJavatechnologyfirstappearedonthescene,theexcitementwasnotaboutawell-craftedprogramminglanguagebutaboutthepossibilityofsafelyexecutingappletsthataredeliveredovertheInternet(seeVolumeI,Chapte
2、r10formoreinformationaboutapplets).Obviously,deliveringexecutableappletsispracticalonlywhentherecipientsaresurethatthecodecan'twreakhavocontheirmachines.Forthisreason,securitywasandisamajorconcernofboththedesignersandtheusersofJavatechnology.Thismeansthatunl
3、ikeotherlanguagesandsystems,wheresecuritywasimplementedasanafterthoughtorareactiontobreak-ins,securitymechanismsareanintegralpartofJavatechnology.Threemechanismshelpensuresafety:Languagedesignfeatures(boundscheckingonarrays,nouncheckedtypeconversions,nopoint
4、erarithmetic,andsoon).Anaccesscontrolmechanismthatcontrolswhatthecodecando(suchasfileaccess,networkaccess,andsoon).Codesigning,wherebycodeauthorscanusestandardcryptographicalgorithmstoauthenticateJavacode.Then,theusersofthecodecandetermineexactlywhocreatedth
5、ecodeandwhetherthecodehasbeenalteredafteritwassigned.Below,you'llseethecryptographicalgorithmssuppliedinthejava.securitypackage,whichallowforcodesigninganduserauthentication.Aswesaidearlier,appletswerewhatstartedthecrazeovertheJavaplatform.Inpractice,peopled
6、iscoveredthatalthoughtheycouldwriteanimatedappletslikethefamous"nervoustext"applet,appletscouldnotdoawholelotofusefulstuffintheJDK1.0securitymodel.Forexample,becauseappletsunderJDK1.0weresocloselysupervised,theycouldn'tdomuchgoodonacorporateintranet,eventhou
7、ghrelativelylittleriskattachestoexecutinganappletfromyourcompany'ssecureintranet.ItquicklybecamecleartoSunthatforappletstobecometrulyuseful,itwasimportantforuserstobeabletoassigndifferentlevelsofsecurity,dependingonwheretheappletoriginated.Ifanappletcomesfro
8、matrustedsupplierandithasnotbeentamperedwith,theuserofthatappletcanthendecidewhethertogivetheappletmoreprivileges.Togivemoretrusttoanapplet,weneedtoknowtwothings:•Wheredidtheappletcomefrom?•Wast
