外文翻译6在桌面应用程序中Bean和数据的绑定.docx

外文翻译6在桌面应用程序中Bean和数据的绑定.docx

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外文翻译6在桌面应用程序中Bean和数据的绑定

BindingBeansandDatainaDesktopApplication

ThisguideisanintroductiontothesupportinNetBeansIDE6.0forbeansbindinganddatabindinginJavadesktopapplications.

SoftwareandFilesNeededfortheTutorial

Forthistutorialyouneedtohavethefollowingsoftwareinstalledonyourcomputer:

NetBeansIDE6.0（download）.

JavaStandardDevelopmentKit（JDK）version5.0or6.0（download）

Introduction:

BeansBindinginNetBeansIDE6.0

Untilthereleaseofthebeansbindinglibrary,itwassomewhatcumbersometoconnectUIcomponentstodatabasesortokeepvaluesofcomponentpropertiesinsync.Forexample,displayingdatafromastandarddatabaseinaJTablerequiredthemanualcreationofutilityclassestohandletheconnectionbetweenthedatabaseandtheJTable.Andkeepingvaluesofdifferentbeanpropertiesinsync（suchasthevalueofaJTextFieldwiththerenderingofavisualbean）requiredhand-codingoflistenersandeventhandlers.

Thebeansbindinglibrarysimplifiesandstandardizesallofthis.Youcanmerelywriteafewlinesofcodetoestablishwhichpropertiesofwhichcomponentsneedtobekeptinsync,andthebeansbindinglibraryhandlestherest.IntheNetBeansIDE,beansbindingfeaturesareintegratedintheGUIBuilder,soyoucanquicklygetthebehaviorofyourapplicationcodedsoonafteryouhaveestablishedthevisualdesign.

ThisguideisanoverviewofthemainaspectsofbeansbindingintheIDE.Foraconcreteexampleofmanyofthesefeatures,youcantrytheBuildingaJavaDesktopDatabaseApplicationtutorial.

BindingPropertiestoOtherProperties

Atitsmostbasic,beansbindingisawaytoconnectbeanpropertieswithoutusingeventlisteningandhandlingcode.

ToillustratetheconceptofbeansbindingandhowtheIDEsupportsit,wewilldoasimpleexamplewhereausercanadjustaslidertochangeanumericalvalueinatextfield.

Tosetuptheexample:

IntheIDE,choose,File>NewProject.

SelecttheJavacategoryandselecttheJavaApplicationtemplate.ClickNext.

IntheNameandLocationpageofthewizard,performthefollowingoperations:

TypeNumberSliderastheprojectname.

LeavetheSetAsMainProjectcheckboxselected.

CleartheCreateMainClasscheckbox.

ClickFinishtoexitthewizardandsetuptheproject.

IntheProjectswindow,right-clicktheNumberSliderprojectnodeandchooseNew>JFrameForm.

（IfJFrameFormisnotavailableintheNewmenu,chooseOther.ThenintheNewFilewizard,selecttheSwingGUIFormscategoryandselecttheJFrameFormtemplate.）

IntheNameandLocationpageofthewizard,performthefollowingoperations:

TypeNumberSliderFramefortheclassname.

Typenumbersliderforthepackagename.

ClickFinishtoexitthewizardandcreatetheform.

NumberSliderForm.javashouldopenindesignmodeintheeditingarea.

FromtheSwingControlssectionofthePalette,dragaslidercomponentintothedesignarea.（IfthePalettewindowisnotopen,chooseWindow>Palette.）

FromthePalette,dragatextfieldcomponenttothedesignarea.

Theresultingformmightlooksomethinglikethescreenshotbelow.However,positioningisnotimportantforpurposesofthisexample.

SourceandTarget

Nowthatwehavesetuptheexample,wearereadytocreatethebinding.However,firstweneedtodeterminewhichcomponentwillbethesourceofthebindingandwhichwillbethetarget.Thebindingsourcecomponentiswhereavalueforthepropertyfirstoriginates.

WhenbindingintheGUIEditor,youinitiateabindingonthetargetandthenyoudeclarethesourceintheBinddialogbox.

Inthiscase,sincetheJSlidercomeswithadefaultrangeofvalues,wewilluseitasthesource.

Note:

Bindingscanbetwo-way（read/write）,sothatchangesinthetargetareautomaticallyreflectedinthesource.However,thedirectionoftheinitialbindingisalwaysfromthesourcetothetarget.SeetheinformationonUpdateModeintheAdvancedBindingConfigurationsection.

Tobindtheslidertothetextfield:

Right-clickthetextfieldcomponentandchooseBind>texttoopentheBinddialogbox.

FromtheBindingSourcecombobox,selectjSlider1.

FromtheBindingExpressioncombobox,selectvalueintasshownintheimagebelow.

ClickOK.

Youhavejustboundthevaluebeanpropertyoftheslidertothetextvalueofthetextfield.

Inthedesignarea,thetextfieldshouldshowthevalue50.Thisvaluereflectsthefactthatthesliderisinthemiddlepositionandthedefaultrangeofvaluesforthesliderisfrom0to100.

Youcannowruntheapplicationandseethebindinginaction.

Toruntheproject:

ChooseRun>RunMainProject.

IntheRunProjectdialogbox,clickOKtoacceptnumberslider.NumberSliderFormasthemainclass.

Theapplicationsshouldstartinaseparatewindow.Adjustthesliderintherunningapplicationandwatchthevaluechangeinthetextfield.

AdvancedBindingConfiguration

Theexampleaboveshowsastraightforwardbindingwithsomedefaultbehaviors.Butsometimesyoumightwantorneedtoconfigureyourbindingdifferently.Ifthatisthecase,youcanusetheAdvancedtaboftheBindingdialogbox.

TheAdvancedtabofthedialogboxcontainsthefollowingfields:

Name.Enablesyoutocreateanameforthebinding,whichgivesyoumoreflexibilityformanagingyourbindings.Thenameisaddedtotheconstructorofthebindingandcanbereferencedwiththebinding'sgetName（）method.

UpdateMode.Specifiesthewaythatthepropertiesarekeptsynchronized.Thepossiblevaluesare:

Alwayssync（read/write）.Wheneverachangeismadetoeitherthesourceorthetarget,theotherisupdated.

Onlyreadfromsource（readonly）.Thetargetisonlyupdatedthefirsttimethesourcevalueisset.Changesthataremadetothesourceareupdatedinthetarget.Changesmadetothetargetarenotupdatedinthesource.

Readfromsourceonce（readonce）.Thetargetisonlyupdatedwhenthetargetandsourceareinitiallybound.

UpdateSourceWhen（availableonlytothetextpropertyofJTextFieldandJTextAreacomponents）.Enablesyoutoselectthefrequencywithwhichthepropertiesaresynchronized.

IgnoreAdjusting（availabletothevaluepropertyofJSlider;totheselectedElementpropertyofJTableandJList;andtotheselectedElementspropertyofJTableandJList）.Ifthischeckboxisselected,anychangesmadetoonepropertyarenotpropagatedtotheotherpropertyuntiltheuserisfinishedmakingthechange.Forexample,whentheapplication'suserdragsaslider,thevalueofthepropertytowhichtheslider'svaluepropertyisboundisonlyupdatedoncetheuserreleasesthemousebutton.

Converter.Ifyourbindinginvolvespropertieswithdifferentdatatypes,youcanspecifycodethatconvertsvaluesbetweenthetypes.Thebeansbindinglibraryhandlesmanycommonlyneededconversions,butyoumightneedtoprovideyourownconvertersforothercombinationsofpropertytypes.Suchconvertersneedtoextendtheorg.jdesktop.beansbinding.Converterclass.

TheConverterdrop-downlistispopulatedwithanyconvertersthathavebeenaddedasbeanstoyourform.Youcanalsoaddtheconversioncodedirectlybyclickingtheellipsis（...）button,andselectingCustomCodefromtheSelectConverterPropertyUsingdrop-downlist.

Validator.Enablesyoutospecifycodetovalidateachangeinthetargetpropertyvaluebeforepropagatingthatchangebacktothesourceproperty.Forexample,youcanuseavalidatortomakesurethatanintegerpropertyvalueiswithinaspecificrange.

Validatorsneedtoextendtheorg.jdesktop.beansbinding.Validatorclass.

TheValidatordrop-downlistispopulatedwithanyvalidatorsthathavebeenaddedasbeanstoyourform.Youcanalsoaddthevalidationcodedirectlybyclickingtheellipsis（...）button,andselectingCustomCodefromtheSelectValidatorPropertyUsingdrop-downlist.

NullSourceValue.Enablesyoutospecifyadifferentvaluetouseifthesourcepropertyhasanullvaluewhenthebindingisattempted.ThisfieldcorrespondswiththesetSourceNullValue（）methodoftheorg.jdesktop.beansbinding.Bindingclass.

UnreadableSourceValue.Enablesyoutospecifyadifferentvaluetouseifthebindingexpressioncannotberesolvedwhenthebindingisattempted.ThisfieldcorrespondswiththesetSourceUnreadableValue（）methodoftheorg.jdesktop.beansbinding.Bindingclass.

Note:

Tobetterunderstandtheclassesandmethodsmentionedabove,youcanaccessthebeansbindingJavadocdocumentationdirectlyfromtheIDE.ChooseHelp>JavadocReferences>BeansBinding.Inthebrowserwindowthatopens,clicktheorg.jdesktop.beansbindinglinktoaccessdocumentationforthoseclasses.

BindingDatatoComponents

OnceyouhavecreatedanewJavaformandaddedcomponentstotheform,youcangeneratecodetobindthosecomponentstodata.TheIDEmakesiteasytobinddatatoSwingJTable,JList,andJComboBoxcomponents.

Beforebindingacomponenttodatafromadatabase,youneedtohavedonethefollowingthings:

ConnectedtoadatabaseintheIDE.

AddedthecomponenttoaformintheGUIBuilder.

Createdclassesthatrepresentthedatabasetablestowhichyouwanttobind.Stepsoncreatingtheentityclassesforbindingdatatoacomponentaregivenbelow.

CreatingEntityClasses

TocreateentityclassestorepresentthedatabasethatistobeboundtotheJTable:

IntheProjectswindow,right-clickyourprojectandchooseNew>Other,selectthePersistencecategory,andselecttheEntityClassesfromDatabasetemplate.

IntheDatabaseTablespageofthewizard,selectthedatabaseconnection.

OncetheAvailableTablescolumnispopulated,selectthetablesthatyouwanttouseinyourapplication