外文翻译-开发Swing应用

0外文原文DevelopingSwingApplicationsThefirstexposureofmanypeopletotheJavaprogramminglanguageisintheformofapplets,smallandsecureJavaprogramsthatrunaspartofawebpage.JavaWebStart,aprotocolfordownloadingandrunningJavaprograms,makesitpossibletorunapplicationsfromawebbrowserasiftheywereapplets.Today,youlearnhowtocreatetheseweb-launchedJavaprogramsasyouexplorethefollowingtopics:1.HowtoinstallandrunJavaapplicationsinawebbrowser2.Howtopublishyourapplicationsfilesandrunit3.HowSwingapplicationscanrunintoperformanceslowdownsontime-consumingtasks4.HowtosolvethisproblembyusingSwingWorker,aclassthatper-formsSwingworkinitsownthreadJavaWebStartOneoftheissuesyoumustdealwithasaJavaprogrammerishowtomakeyoursoft-wareavailabletoyourusers.JavaapplicationsrequireaJavainterpreter,soonemusteitherbeincludedwiththeappli-cationorpreviouslyinstalledonthecomputer.Lackingeitherofthose,usersmustinstallaninterpreterthemselves.Theeasiestsolution(foryou)istorequirethatusersdownloadandinstalltheJavaRuntimeEnvironmentfromSunswebsiteat.Regardlessofhowyoudealwiththerequirementforaninterpreter,youdistributeanapplicationlikeanyotherprogram,makingitavailableonaCD,website,orsomeothermeans.Ausermustrunaninstallationprogramtosetitup,ifoneisavailable,orcopythefilesandfoldersmanually.Javaappletsareeasiertomakeavailablebecausetheycanberunbywebbrowsers.However,ifyourprogramisaJavaapplet,usersmustberunningbrowsersequippedwiththeJavaPlug-in.ThistoocanbedownloadedfromSunaspartoftheJavaRuntimeEnvironment.Thereareseveraldrawbackstoofferingappletsinsteadofapplications.Thebiggestisthedefaultsecuritypolicyforapplets,whichmakesitimpossibleforthemtoreadandwritedataonauserscomputer,amongotherrestrictions.1JavaeasesthechallengesofsoftwaredeploymentwithJavaWebStart,ameansofrun-ningJavaapplicationspresentedonawebpageandstoredonawebserver.Hereshowitworks:1.AprogrammerpackagesanapplicationandallthefilesitneedsintoaJARarchivealongwithafilethatusestheJavaNetworkLaunchingProtocol(JNLP),partofJavaWebStart.2.Thefileisstoredonawebserverwithawebpagethatlinkstothatfile.3.Auserloadsthepagewithabrowserandclicksthelink.4.IftheuserdoesnothavetheJavaRuntimeEnvironment,adialogboxopensaskingwhetheritshouldbedownloadedandinstalled.Thefullinstallationismorethan65Minsizeandcouldtake3045minutestodownloadona56KInternetconnection(or35minutesonahigh-speedconnection).5.TheJavaRuntimeEnvironmentinstallsandrunstheprogram,openingnewframesandotherinterfacecomponentslikeanyotherapplication.Theprogramissavedinacache,soitcanberunagainlaterwithoutrequiringinstallation.Toseeitinaction,visitSunsJavaWebStartsiteat/products/javawebstartandclicktheCodeSamples&Appslink,andthenthe“Demos”link.TheWebStartDemospagecontainspicturesofseveralJavaapplications,eachwithaLaunchbuttonyoucanusetoruntheapplication,asshowninFigure14.1.PresentingWebStartapplicationsonawebpage.ClicktheLaunchbuttonofoneoftheapplications.IfyoudonthavetheJavaRuntimeEnvironmentyet,adialogboxopensaskingwhetheryouwanttodownloadandinstallit.TheruntimeenvironmentincludestheJavaPlug-in,aJavainterpreterthataddssupportforthecurrentversionofthelanguagetobrowserssuchasMicrosoftInternetExplorerandMozilla.Theenvironmentalsocanbeusedtorunapplications,regardlessofwhethertheyuseJavaWebStart.WhenanapplicationisrunusingJavaWebStart,atitlescreendisplaysonyourcom-puterbriefly,andtheapplicationsgraphicaluserinterfaceappears.IfyouhaveinstalledtheJDK,youarelikelytohavetheJavaNOTE:RuntimeEnvironmentonyourcomputeralready.Figure14.2showsoneofthedemoapplicationsofferedbySun,amilitarystrategygameinwhichthreeblackdotsattempttokeepareddotfrommovingintotheirterritory.Iftheuserdoesnotpermitsomething,theapplicationcannotfunctionfully.The2kindsofthingsthattriggerasecuritydialogboxarethesamethingsnotallowedbydefaultinapplets:readingandwritingfiles,loadingnetworkresourcesfromserversotherthantheonehostingtheprogram,andthelike.AfteranapplicationhasbeenrunbyJavaWebStart,itisstoredonauserscomputerinacache,enablingittoberunagainlaterwithoutinstallation.Theonlyexceptioniswhenanewversionoftheapplicationbecomesavailable.Inthiscase,thenewversionisdownloadedandinstalledautomaticallyinplaceoftheexistingone.AJavaWebStartapplicationviewercanberundirectlytoseetheapplicationsthathavebeencached,runthem,andchangesomeoftheirsettings.Theapplicationiscalledjavaws.exeandcanbefoundinthesamefolderasjavaandtheothercommand-lineprogramsintheJDK.TherealsoshouldbeamenuitemforJavaWebStartthatwasaddedduringinstallation.AlthoughyourunaJavaWebStartapplicationforthefirsttimeNOTEusingawebbrowser,thatsnotarequirement.Toseethis,runtheJavaWebStartapplicationviewer,selectaprogram,andchooseApplication,InstallShortcuts.Ashortcuttoruntheapplicationwillbeaddedtoyourdesktop.Youcanuseittoruntheprogramwith-outabrowser.ThedefaultsecurityrestrictionsinplaceforaJavaWebStartapplicationcanbeoverrid-denifitisstoredinadigitallysignedJavaarchive.Theuserwillbepresentedwiththesignedsecuritycertificate,whichdocumentstheauthoroftheprogramandthecertificategrantingauthorityvouchingforitsidentity,andaskedwhethertoacceptitorrejectit.Theapplicationwontrununlessthecertificatehasbeenaccepted.UsingJavaWebStartAnyJavaapplicationcanberunusingJavaWebStartaslongasthewebserverthatofferstheapplicationisconfiguredtoworkwiththetechnologyandalltheclassfilesandotherfilesitneedshavebeenpackagedtogether.ToprepareanapplicationtouseJavaWebStart,youmustsavetheapplicationsfilesinaJavaarchivefile,createaspecialJavaWebStartconfigurationfilefortheapplication,anduploadthefilestothewebserver.TheconfigurationfilethatmustbecreatedusesJavaNetworkLaunchingProtocol(JNLP),anExtensibleMarkupLanguage(XML)fileformatthatspecifiestheapplica-tionsmainclassfile,itsJARarchive,andotherthingsabouttheprogram.XMLisintroducedduringDay20,“XMLWebServices.”NOTE:theformatofJNLPfilesisrelativelyself-explanatory,youdontneedtoknowmuchaboutXMLtocreateaJNLPfile.ThenextprojectyouwillundertakeistouseJavaWebStarttolaunchandrunPageData,3anapplicationthatdisplaysinformationaboutwebpages.TheapplicationrequiresthePageData.classfile,whichcanbedownloadedfromtheDay14pageofthebookswebsiteat.(YoualsomightwantPageData.javaincaseyoudecidetomakeanychangestotheapplication.)Togetready,putacopyofthatprojectsclassfileinthefolderyouareusingasawork-spaceforyourJavaprogramming.CreatingaJNLPFileThefirstthingyoumustdoispackageallofanapplicationsclassfilesintoaJavaarchivefilealongwithanyotherfilesitneeds.IfyouareusingtheJDK,youcancreatetheJARfilewiththefollowingcommand:jar-cfPageData.jarPageData.classAJARfilecalledPageData.jariscreatedthatholdstheclassfile.Next,youshouldcreateanicongraphicfortheapplication,whichwillbedisplayedwhenitisloadedandusedasitsiconinmenusanddesktops.TheiconcanbeineitherGIForJPEGformatandshouldbe64pixelswideby64pixelstall.Forthisproject,ifyoudontwanttocreateanewicon,youcandownloadpagedataicon.giffromthebookswebsite.GotoandopetheDay14page.Right-clickthepagedataicon.giflinkandsavethefiletothesamefolderasyourPageData.jarfile.ThefinalthingyoumustdoiscreatetheJNLPfilethatdescribestheapplication.Listin14.1containsaJNLPfileusedtodistributethePageDataapplication.Openyourwordprocessorandenterthetextofthislisting;thensavethefileasPageData.jnlp.ThestructureofaJNLPfileissimilartotheHypertextMarkupLanguage(HTML)requiredtoputaJavaappletonawebpage.Everythingwithinthemarksisatag,andtagsareplacedaroundtheinformationthetagdescribes.Theresanopeningtagbeforetheinformationandaclosingtagafterit.Forexample,line7ofListing14.1containsthefollowingtext:PageDataApplicationInorderfromlefttoright,thislinecontainstheopeningtag,thetextPageDataApplication,andtheclosingtag.Thetextbetweenthetags,“PageDataApplication,”isthetitleoftheapplication.ThistitlewillbedisplayedbyJavaWebStartastheapplicationisbeingloadedandusedinmenusandshortcuts.Thedifferencebetweenopeningtagsandclosingtagsisthatclosingtagsbeginwithaslash(/)character,andopeningtagsdonot.Inline8,istheopeningtag,istheclosingtag,andthesetagssurroundthenameofthevendorwhocre-atedtheapplication.Iveusedmynamehere.Deleteitandreplaceitwithyourown14name,takingcarenottoaltertheortagsaroundit.Sometagshaveanopeningtagonly,suchasline11:4Theoffline-allowedtagindicatesthattheapplicationcanberuneveniftheuserisnotconnectedtotheInternet.IfitwasomittedfromtheJNLPfile,theoppositewouldbetrue,andtheuserwouldbeforcedtogoonlinebeforerunningthisapplication.InXML,alltagsthatdonothaveaclosingtagendwith/insteadof.Tagsalsocanhaveattributes,whichareanotherwaytodefineinformationinanXMLfile.Anattributeisanameinsideatagthatisfollowedbyanequalsignandsometextwithinquotes.Forexample,considerline9ofListing14.1:Thisisthehomepagetag,andithasoneattribute,href.Thetextbetweenthequotemarksisusedtosetthevalueofthisattributeto.Thisdefinesthehomepageoftheapplicationthewebpagethatusersshouldvisitiftheywanttoreadmoreinformationabouttheprogramandhowitworks.ThePageDataJNLPfiledefinesasimpleJavaWebStartapplicationthatrunswithnosecurityrestrictions,asdefinedinlines1719:Inadditiontothetagsthathavealreadybeendescribed,Listing14.1definesotherinfor-mationrequiredbyJavaWebStart.Line1designatesthatthefileusesXMLandtheUTF-8characterset.ThissamelinecanbeusedonanyoftheJNLPfilesyoucreateforapplications.Line2isacomment.LikeothercommentsinJava,itsplacedinthefilesolelyforthebenefitofhumans.JavaWebStartignoresit.Thejnlpelement,whichbeginsonline3andendsonline21,mustsurroundalltheothertagsthatconfigureWebStart.Thistaghastwoattributes,codebaseandhref,whichindicatewheretheJNLPfileforthisapplicationcanbefound.Thecodebaseattributeistheuniformresourcelocator(URL)ofthefolderthatcontainstheJNLPfile.ThehrefattributeisthenameofthefileorarelativeURLthatincludesafolderandthename(suchas“pub/PageData.jnlp”).AccessingDatabaseswithJDBCAlmostallJavaprogramsdealwithdatainsomeway.Youhaveusedprimitivetypes,objects,arrays,linkedlists,andotherdatastructuresuptothispoint.TodayyouworkwithdatainamoresophisticatedwaybyexploringJavaDatabaseConnectivity5(JDBC),aclasslibrarythatconnectsJavapro-gramstorelationaldatabases.Java6includesJavaDB,asmallrelationaldatabasethatspartoftheJavaDevelopmentKit,makingiteasierthanevertoincorporateadata-baseintoyourapplications.TodayyouexploreJDBCandExtensibleMarkupLanguage(XML)inthefol-lowingways:1.UsingJDBCdriverstoworkwithdifferentrelationaldatabases2.AccessingadatabasewithStructuredQueryLanguage(SQL)3.ReadingrecordsfromadatabaseusingSQLandJDBC4.AddingrecordstoadatabaseusingSQLandJDBC5.CreatinganewJavaDBdatabaseandreadingitsrecordsJavaDatabaseConnectivityJavaDatabaseConnectivity(JDBC)isasetofclassesthatcanbeusedtodevelopclient/serverapplicationsthatworkwithdatabasesdevelopedbyMicrosoft,Sybase,Oracle,Informix,andothersources.WithJDBC,youcanusethesamemethodsandclassesinJavaprogramstoreadandwriterecordsandperformotherkindsofdatabaseaccess.Aclasscalledadriveractsasabridgetothedatabasesourcetherearedriversforeachofthepopulardatabases.Client/serversoftwareconnectsauserofinformationwithaproviderofthatinformation,anditsoneofthemostcommonplaceformsofprogramming.YouuseiteverytimeyousurftheWeb:Awebbrowserclientrequestspages,imagefiles,andotherdocumentsusingauniformresourcelocator,orURL.Webserversprovidetherequestedinforma-tion,ifitcanbefound,fortheclient.Oneofthebiggestobstaclesfacedbydatabaseprogrammersisthewidevarietyofdata-baseformatsinuse,eachwithitsownproprietarymethodofaccessingdata.Tosimplifyusingrelationaldatabaseprograms,astandardlanguagecalledSQL(StructuredQueryLanguage)hasbeenintroduced.Thislanguagesupplantstheneedtolearndifferentdatabase-queryinglanguagesforeachdatabaseformat.JavaDB,thedata-baseincludedinJava6,supportsSQL.Indatabaseprogramming,arequestforrecordsinadatabaseiscalledaquery.UsingSQL,youcansendcomplexqueriestoadatabaseandgettherecordsyourelookingforinanyorderyouspecify.Considertheexampleofadatabaseprogrammeratastudentloancompanywhohasbeenaskedtoprepareareportonthemostdelinquentloanrecipients.TheprogrammercoulduseSQLtoqueryadatabaseforallrecordsinwhichthelastpaymentwasmorethan180daysagoandtheamountdueismorethan$0.00.SQLalsocanbeusedtocontrolthe6orderinwhichrecordsarereturned,sotheprogrammercangettherecordsintheorderofSocialSecuritynumber,recipientname,amountowed,oranotherfieldintheloandatabase.AllthisispossiblewithSQLtheprogrammerdoesntneedanyoftheproprietarylan-guagesassociatedwithpopulardatabaseformats.SQListheindustry-standardapproachtoaccessingrelationaldatabases.JDBCsupportsSQL,enablingdeveloperstouseawiderangeofdatabaseformatswithoutknowingthespecificsoftheunderlyingdatabase.JDBCalsosupportstheuseofdatabasequeriesspe-cifictoadatabaseformat.TheJDBCclasslibrarysapproachtoaccessingdatabaseswithSQLiscomparabletoexistingdatabase-developmenttechniques,sointeractingwithanSQLdatabasebyusingJDBCisntmuchdifferentthanusingtraditionaldatabasetools.JavaprogrammerswhoalreadyhavesomedatabaseexperiencecanhitthegroundrunningwithJDBC.TheJDBClibraryincludesclassesforeachofthetaskscommonlyassociatedwithdata-baseusage:1.Makingaconnectiontoadatabase2.CreatingastatementusingSQL3.ExecutingthatSQLqueryinthedatabase4.ViewingtheresultingrecordsTheseJDBCclassesareallpartofthejava.sqlpackage.ConnectingtoanODBCDataSourceYourfirstprojecttodayisaJavaapplicationthatusesaJDBC-ODBCbridgetoconnecttoanAccessfile.TheAccessfileforthisprojectisworld20.mdb,adatabaseofworldenergystatisticspublishedbytheU.S.EnergyInformationAdministration.TheCoaltableinthisdata-baseincludesthreefieldsyouwillbeusingintheproject:1.Country2.Year3.AnthraciteProductionThedatabaseusedinthisprojectisincludedonthisbooksofficialwebsiteat.Tousethisdatabase,youmusthaveanODBCdriveronyoursystemthatsupportsAccessfiles.UsingtheODBCDataSourceAdministrator(orasimilarprogramifyoureonanon-Windowssystem),youmustcreateanewODBCdatasource7associatedwithworld20.mdb.OthersetupworkmightbeneededdependingontheODBCdriverspresentonyoursys-tem,ifany.ConsultthedocumentationincludedwiththeODBCdriver.Afteryouhavedownloadedworld20.mdbtoyourcomputerorfoundanotherdatabasethatscompatiblewiththeODBCdriversonyoursystem,thefinalstepingettingthefilereadyforJDBC-ODBCistocreateadatasourceassociatedwithit.Unlikeotherinput-outputclassesinJava,JDBCdoesntuseafilenametoidentifyadatafileanduseitscontents.Instead,atoolsuchastheODBCDataSourceAdministratorisusedtonametheODBCsourceandindicatethefilefolderwhereitcanbefound.IntheODBCDataSourceAdministrator,clicktheUserDSNtabtoseealistofdatasourcesthatareavailable.Toaddanewoneassociatedwithworld20.mdb(oryourowndatabase),clicktheAddbutton,chooseanODBCdriver,andthenclicktheFinishbutton.ASetupwindowopensthatyoucanusetoprovideaname,shortdescription,andotherinformationaboutthedatabase.ClicktheSelectbuttontofindandchoosethedatabasefile.Figure18.3showstheSetupwindowusedtosetupworld20.mdbasadatasourceintheODBCDataSourceAdministrator.AfteradatabasehasbeenassociatedwithanODBCdatasource,workingwithitinaJavaprogramisrelativelyeasyifyouareconversantwithSQL.ThefirsttaskinaJDBCprogramistoloadthedriver(ordrivers)thatwillbeusedtoconnecttoadatasource.AdriverisloadedwiththeClass.forName(String)method.Class,partofthejava.langpackage,canbeusedtoloadclassesintotheJavainter-preter.TheforName(String)methodloadstheclassnamedbythespecifiedstring.AClassNotFoundExceptioncanbethrownbythismethod.AllprogramsthatuseanODBCdatasourceusesun.jdbc.odbc.JdbcOdbcDriver,theJDBC-ODBCbridgedriverincludedwithJava.LoadingthisclassintoaJavainterpreterrequiresthefollowingstatement:Class.forName(“sun.jdbc.odbc.JdbcOdbcDriver”);Afterthedriverhasbeenloaded,youcanestablishaconnectiontothedatasourcebyusingtheDriverManagerclassinthejava.sqlpackage.ThegetConnection(String,String,String)methodofDriverManagercanbeusedtosetuptheconnection.ItreturnsareferencetoaConnectionobjectrepresentinganactivedataconnection.Thethreeargumentsofthismethodareasfollows:81.Anameidentifyingthedatasourceandthetypeofdatabaseconnectivityusedtoreachit2.Ausername3.ApasswordThelasttwoitemsareneededonlyifthedatasourceissecuredwithausernameandapassword.Ifnot,theseargumentscanbenullstrings(“”).Thenameofthedatasourceisprecededbythetextjdbc:odbc:whenusingtheJDBC-ODBCbridge,whichindicatesthetypeofdatabaseconnectivityinuse.ThefollowingstatementcouldbeusedtoconnecttoadatasourcecalledPayrollwithausernameof“Doc”andapasswordof“1rover1”:Connectionpayday=DriverManager.getConnection(“jdbc:odbc:Payroll”,“Doc”,“1rover1”);Afteryouhaveaconnection,youcanreuseiteachtimeyouwanttoretrieveorstoreinformationfromthatconnectionsdatasource.ThegetConnection()methodandallotherscalledonadatasourcethrowSQLExceptionerrorsifsomethinggoeswrongasthedatasourceisbeingused.SQLhasitsownerrormessages,andtheyarepassedalongaspartofSQLExceptionobjects.9中文翻译开发Swing应用很多人第一次接触到Java编程语言是小程序，小而安全的Java程序，作为一部分运行的形式网页。JavaWebStart的，一个协议下载和运行Java程序，使得它可以从web浏览器中运行的应用程序，如果他们小程序。今天，您将学习如何创建这些网站推出的Java程序,探讨以下议题：如何安装和在Web浏览器中运行的Java应用程序如何发布您的应用程序的文件并运行它如何Swing应用程序可以在遇到性能下降耗时的任务如何通过使用SwingWorker类，一类解决这个问题的每形式工作摆在它自己的线程JavaWebStart一个你必须处理作为一个Java程序员的问题是如何让你的软洁具提供给用户。Java应用程序需要一个Java解释器，因此必须要么被包含在APPLI阳离子或以前安装在计算机上。缺少其中任何一门，用户必须安装一个解释自己。最简单的解决方案，是要求用户下载。从Sun的网站安装Java运行时环境。不管你如何处理传译员的要求，你分发像任何其他程序，使其成为一个光盘，网站或其他一些可用的应用程序表示。用户必须运行一个安装程序来进行设置，如果有的话，或复制手动的文件和文件夹。Java小程序更容易使用，因为他们可以通过Web浏览器中运行。但是，如果你的程序是一个Java小程序，用户必须运行浏览器的装备与Java插件。这也可以从Sun下载的Java运行时的一部分环境。有几个缺点，以提供小应用程序，而不是应用程序。跌幅最大的是该默认安全策略为小应用程序，这使得他们无法读取和写入用户的计算机，以及其他限制的数据。简化的Java软件部署的挑战使用JavaWebStart，运行的一种手段宁Java应用程序呈现在网页上，并存储在Web服务器上。下面是它的工作原理：1，程序员打包应用程序和所有文件，它需要成为一个JAR归档随着使用Java网络启10动协议（JNLP）文件的一部分，JavaWebStart的。2，该文件存储在Web服务器上有一个网页链接到该文件。3，用户加载页面浏览器，并点击该链接。4，如果用户没有Java运行时环境，将打开一个对话框，询问是否应被下载和安装。完整的安装超过大小65M，可能需要30-45分钟才能下载一个56K互联网连接化（或3-5分钟上高速连接）。5，Java运行时环境安装并运行程序，打开新的框架和其他界面组件，像任何其他应用程序。该程序将保存在一个高速缓存，因此它可以稍后再无需安装即可运行。要看到它在行动，请访问Sun的JavaWebStart的网站/products/JavaWebStart中，然后单击代码示例和应用程序的链接，然后在“演示”链接。该WebStart的演示页面包含多个Java应用程序，每一个启动画面按钮，您可以用它来运行应用程序，启动应用程序在网页上。点击其中一个应用程序的启动按钮。如果您没有Java运行时环境还，将会打开一个对话框，询问您是否要下载并安装它。运行时环境包括Java插件，Java解释，增加了支持对于语言，以浏览器，如MicrosoftInternetExplorer的最新版本和Mozilla。环境还可以用于是否运行的应用程序，而不管他们使用JavaWebStart的。当一个应用程序使用JavaWebStart，一个在你