翻譯文獻-使用 oracle 對象類型

外文原文WORKINGWITHORACLEOBJECTTYPESTHISCHAPTERDESCRIBESJDBCSUPPORTFORUSERDEFINEDOBJECTTYPESITDISCUSSESFUNCTIONALITYOFTHEGENERIC,WEAKLYTYPEDORACLESQLSTRUCTCLASS,ASWELLASHOWTOMAPTOCUSTOMJAVACLASSESTHATIMPLEMENTEITHERTHEJDBCSTANDARDSQLDATAINTERFACEORTHEORACLEORADATAINTERFACETHISCHAPTERALSODESCRIBESHOWJDBCDRIVERSACCESSSQLJOBJECTTYPESINSQLREPRESENTATIONTHEFOLLOWINGTOPICSARECOVERED_MAPPINGORACLEOBJECTS_USINGTHEDEFAULTSTRUCTCLASSFORORACLEOBJECTS_CREATINGANDUSINGCUSTOMOBJECTCLASSESFORORACLEOBJECTS_OBJECTTYPEINHERITANCE_USINGJPUBLISHERTOCREATECUSTOMOBJECTCLASSES_DESCRIBINGANOBJECTTYPE_SQLJOBJECTTYPESNOTEFORGENERALINFORMATIONABOUTORACLEOBJECTFEATURESANDFUNCTIONALITY,SEETHEORACLE9IAPPLICATIONDEVELOPERSGUIDEOBJECTRELATIONALFEATURESMAPPINGORACLEOBJECTSORACLEOBJECTTYPESPROVIDESUPPORTFORCOMPOSITEDATASTRUCTURESINTHEDATABASEFOREXAMPLE,YOUCANDEFINEATYPEPERSONTHATHASATTRIBUTESSUCHASNAMETYPECHAR,PHONENUMBERTYPECHAR,ANDEMPLOYEENUMBERTYPENUMBERORACLEPROVIDESTIGHTINTEGRATIONBETWEENITSORACLEOBJECTFEATURESANDITSJDBCFUNCTIONALITYYOUCANUSEASTANDARD,GENERICJDBCTYPETOMAPTOORACLEOBJECTS,ORYOUCANCUSTOMIZETHEMAPPINGBYCREATINGCUSTOMJAVATYPEDEFINITIONCLASSESINTHISBOOK,JAVACLASSESTHATYOUCREATETOMAPTOORACLEOBJECTSWILLBEREFERREDTOASCUSTOMJAVACLASSESOR,MORESPECIFICALLY,CUSTOMOBJECTCLASSESTHISISASOPPOSEDTOCUSTOMREFERENCESCLASSESTOMAPTOOBJECTREFERENCES,ANDCUSTOMCOLLECTIONCLASSESTOMAPTOORACLECOLLECTIONSCUSTOMOBJECTCLASSESCANIMPLEMENTEITHERASTANDARDJDBCINTERFACEORANORACLEEXTENSIONINTERFACETOREADANDWRITEDATAJDBCMATERIALIZESORACLEOBJECTSASINSTANCESOFPARTICULARJAVACLASSESTWOMAINSTEPSINUSINGJDBCTOACCESSORACLEOBJECTSARE1CREATINGTHEJAVACLASSESFORTHEORACLEOBJECTS,AND2POPULATINGTHESECLASSESYOUHAVETWOOPTIONSLETJDBCMATERIALIZETHEOBJECTASASTRUCTTHISISDESCRIBEDIN“USINGTHEDEFAULTSTRUCTCLASSFORORACLEOBJECTS“ONPAGE93OREXPLICITLYSPECIFYTHEMAPPINGSBETWEENORACLEOBJECTSANDJAVACLASSESTHISINCLUDESCUSTOMIZINGYOURJAVACLASSESFOROBJECTDATATHEDRIVERTHENMUSTBEABLETOPOPULATEINSTANCESOFTHECUSTOMOBJECTCLASSESTHATYOUSPECIFYTHISIMPOSESASETOFCONSTRAINTSONTHEJAVACLASSESTOSATISFYTHESECONSTRAINTS,YOUCANDEFINEYOURCLASSESTOIMPLEMENTEITHERTHEJDBCSTANDARDJAVASQLSQLDATAINTERFACEORTHEORACLEEXTENSIONORACLESQLORADATAINTERFACETHISISDESCRIBEDIN“CREATINGANDUSINGCUSTOMOBJECTCLASSESFORORACLEOBJECTS“ONPAGE910YOUCANUSETHEORACLEJPUBLISHERUTILITYTOGENERATECUSTOMJAVACLASSESUSINGTHEDEFAULTSTRUCTCLASSFORORACLEOBJECTSIFYOUCHOOSENOTTOSUPPLYACUSTOMJAVACLASSFORYOURSQLJAVAMAPPINGFORANORACLEOBJECT,THENORACLEJDBCWILLMATERIALIZETHEOBJECTASANINSTANCEOFTHEORACLESQLSTRUCTCLASSYOUWOULDTYPICALLYWANTTOUSESTRUCTOBJECTS,INSTEADOFCUSTOMJAVAOBJECTS,INSITUATIONSWHEREYOUAREMANIPULATINGSQLDATAFOREXAMPLE,YOURJAVAAPPLICATIONMIGHTBEATOOLTOMANIPULATEARBITRARYOBJECTDATAWITHINTHEDATABASE,ASOPPOSEDTOBEINGANENDUSERAPPLICATIONYOUCANSELECTDATAFROMTHEDATABASEINTOSTRUCTOBJECTSANDCREATESTRUCTOBJECTSFORINSERTINGDATAINTOTHEDATABASESTRUCTOBJECTSCOMPLETELYPRESERVEDATA,BECAUSETHEYMAINTAINTHEDATAINSQLFORMATUSINGSTRUCTOBJECTSISMOREEFFICIENTANDMOREPRECISEINTHESESITUATIONSWHEREYOUDONTNEEDTHEINFORMATIONINACONVENIENTFORMSTRUCTCLASSFUNCTIONALITYTHISSECTIONDISCUSSESSTANDARDVERSUSORACLESPECIFICFEATURESOFTHEORACLESQLSTRUCTCLASS,INTRODUCESSTRUCTDESCRIPTORS,ANDLISTSMETHODSOFTHESTRUCTCLASSTOGIVEANOVERVIEWOFITSFUNCTIONALITYSTANDARDJAVASQLSTRUCTMETHODSIFYOURCODEMUSTCOMPLYWITHSTANDARDJDBC20,THENUSEAJAVASQLSTRUCTINSTANCEORACLEJDBC2STRUCTUNDERJDK11X,ANDUSETHEFOLLOWINGSTANDARDMETHODSGETATTRIBUTESMAPRETRIEVESTHEVALUESOFTHEATTRIBUTES,USINGENTRIESINTHESPECIFIEDTYPEMAPTODETERMINETHEJAVACLASSESTOUSEINMATERIALIZINGANYATTRIBUTETHATISASTRUCTUREDOBJECTTYPETHEJAVATYPESFOROTHERATTRIBUTEVALUESWOULDBETHESAMEASFORAGETOBJECTCALLONDATAOFTHEUNDERLYINGSQLTYPETHEDEFAULTJDBCTYPESGETATTRIBUTESTHISISTHESAMEASTHEPRECEDINGGETATTRIBUTESMAPMETHOD,EXCEPTITUSESTHEDEFAULTTYPEMAPFORTHECONNECTIONGETSQLTYPENAMERETURNSAJAVASTRINGTHATREPRESENTSTHEFULLYQUALIFIEDNAMESCHEMASQL_TYPE_NAMEOFTHEORACLEOBJECTTYPETHATTHISSTRUCTREPRESENTSSUCHASSCOTTEMPLOYEEORACLEORACLESQLSTRUCTCLASSMETHODSIFYOUWANTTOTAKEADVANTAGEOFTHEEXTENDEDFUNCTIONALITYOFFEREDBYORACLEDEFINEDMETHODS,THENUSEANORACLESQLSTRUCTINSTANCETHEORACLESQLSTRUCTCLASSIMPLEMENTSTHEJAVASQLSTRUCTINTERFACEORACLEJDBC2STRUCTINTERFACEUNDERJDK11XANDPROVIDESEXTENDEDFUNCTIONALITYBEYONDTHEJDBC20STANDARDTHESTRUCTCLASSINCLUDESTHEFOLLOWINGMETHODSINADDITIONTOSTANDARDSTRUCTFUNCTIONALITYGETORACLEATTRIBUTESRETRIEVESTHEVALUESOFTHEVALUESARRAYASORACLESQLOBJECTSGETDESCRIPTORRETURNSTHESTRUCTDESCRIPTOROBJECTFORTHESQLTYPETHATCORRESPONDSTOTHISSTRUCTOBJECTGETJAVASQLCONNECTIONRETURNSTHECURRENTCONNECTIONINSTANCEJAVASQLCONNECTIONTOJDBCCONSULTSTHEDEFAULTTYPEMAPOFTHECONNECTION,TODETERMINEWHATCLASSTOMAPTO,ANDTHENUSESTOCLASSTOJDBCMAPCONSULTSTHESPECIFIEDTYPEMAPTODETERMINEWHATCLASSTOMAPTO,ANDTHENUSESTOCLASSSTRUCTDESCRIPTORSCREATINGANDUSINGASTRUCTOBJECTREQUIRESADESCRIPTORANINSTANCEOFTHEORACLESQLSTRUCTDESCRIPTORCLASSTOEXISTFORTHESQLTYPESUCHASEMPLOYEETHATWILLCORRESPONDTOTHESTRUCTOBJECTYOUNEEDONLYONESTRUCTDESCRIPTOROBJECTFORANYNUMBEROFSTRUCTOBJECTSTHATCORRESPONDTOTHESAMESQLTYPESTRUCTDESCRIPTORSAREFURTHERDISCUSSEDIN“CREATINGSTRUCTOBJECTSANDDESCRIPTORS“ONPAGE94CREATINGSTRUCTOBJECTSANDDESCRIPTORSTHISSECTIONDESCRIBESHOWTOCREATESTRUCTOBJECTSANDDESCRIPTORSANDLISTSUSEFULMETHODSOFTHESTRUCTDESCRIPTORCLASSSTEPSINCREATINGSTRUCTDESCRIPTORANDSTRUCTOBJECTSTHISSECTIONDESCRIBESHOWTOCONSTRUCTANORACLESQLSTRUCTOBJECTFORAGIVENORACLEOBJECTTYPETOCREATEASTRUCTOBJECT,YOUMUSTCREATEASTRUCTDESCRIPTOROBJECTIFONEDOESNOTALREADYEXISTFORTHEGIVENORACLEOBJECTTYPEUSETHESTRUCTDESCRIPTORTOCONSTRUCTTHESTRUCTOBJECTASTRUCTDESCRIPTORISANINSTANCEOFTHEORACLESQLSTRUCTDESCRIPTORCLASSANDDESCRIBESATYPEOFORACLEOBJECTSQLSTRUCTUREDOBJECTONLYONESTRUCTDESCRIPTORISNECESSARYFOREACHORACLEOBJECTTYPETHEDRIVERCACHESSTRUCTDESCRIPTOROBJECTSTOAVOIDRECREATINGTHEMIFTHETYPEHASALREADYBEENENCOUNTEREDBEFOREYOUCANCONSTRUCTASTRUCTOBJECT,ASTRUCTDESCRIPTORMUSTFIRSTEXISTFORTHEGIVENORACLEOBJECTTYPEIFASTRUCTDESCRIPTOROBJECTDOESNOTEXIST,YOUCANCREATEONEBYCALLINGTHESTATICSTRUCTDESCRIPTORCREATEDESCRIPTORMETHODTHISMETHODREQUIRESYOUTOPASSINTHESQLTYPENAMEOFTHEORACLEOBJECTTYPEANDACONNECTIONOBJECTSTRUCTDESCRIPTORSTRUCTDESCSTRUCTDESCRIPTORCREATEDESCRIPTORSQL_TYPE_NAME,CONNECTIONWHERESQL_TYPE_NAMEISAJAVASTRINGCONTAININGTHENAMEOFTHEORACLEOBJECTTYPESUCHASEMPLOYEEANDCONNECTIONISYOURCONNECTIONOBJECTONCEYOUHAVEYOURSTRUCTDESCRIPTOROBJECTFORTHEORACLEOBJECTTYPE,YOUCANCONSTRUCTTHESTRUCTOBJECTTODOTHIS,PASSINTHESTRUCTDESCRIPTOR,YOURCONNECTIONOBJECT,ANDANARRAYOFJAVAOBJECTSCONTAININGTHEATTRIBUTESYOUWANTTHESTRUCTTOCONTAINSTRUCTSTRUCTNEWSTRUCTSTRUCTDESC,CONNECTION,ATTRIBUTESWHERESTRUCTDESCISTHESTRUCTDESCRIPTORCREATEDPREVIOUSLY,CONNECTIONISYOURCONNECTIONOBJECT,ANDATTRIBUTESISANARRAYOFTYPEJAVALANGOBJECTUSINGSTRUCTDESCRIPTORMETHODSASTRUCTDESCRIPTORCANBETHOUGHTOFASA“TYPEOBJECT“THISMEANSTHATITCONTAINSINFORMATIONABOUTTHEOBJECTTYPE,INCLUDINGTHETYPECODE,THETYPENAME,ANDHOWTOCONVERTTOANDFROMTHEGIVENTYPEREMEMBER,THERESHOULDBEONLYONESTRUCTDESCRIPTOROBJECTFORANYONEORACLEOBJECTTYPEYOUCANTHENUSETHATDESCRIPTORTOCREATEASMANYSTRUCTOBJECTSASYOUNEEDFORTHATTYPETHESTRUCTDESCRIPTORCLASSINCLUDESTHEFOLLOWINGMETHODSGETNAMERETURNSTHEFULLYQUALIFIEDSQLTYPENAMEOFTHEORACLEOBJECTTHATIS,INSCHEMASQL_TYPE_NAMEFORMAT,SUCHASCORPORATEEMPLOYEEGETLENGTHRETURNSTHENUMBEROFFIELDSINTHEOBJECTTYPEGETMETADATARETURNSTHEMETADATAREGARDINGTHISTYPELIKETHEGETMETADATAMETHODOFARESULTSETOBJECTTHERETURNEDRESULTSETMETADATAOBJECTCONTAINSTHEATTRIBUTENAME,ATTRIBUTETYPECODE,ANDATTRIBUTETYPEPRECISIONINFORMATIONTHE“COLUMN“INDEXINTHERESULTSETMETADATAOBJECTMAPSTOTHEPOSITIONOFTHEATTRIBUTEINTHESTRUCT,WITHTHEFIRSTATTRIBUTEBEINGATINDEX1THEGETMETADATAMETHODISFURTHERDISCUSSEDIN“FUNCTIONALITYFORGETTINGOBJECTMETADATA“ONPAGE949SERIALIZABLESTRUCTDESCRIPTORSAS“STEPSINCREATINGSTRUCTDESCRIPTORANDSTRUCTOBJECTS“ONPAGE94EXPLAINS,WHENYOUCREATEASTRUCTOBJECT,YOUFIRSTMUSTCREATEASTRUCTDESCRIPTOROBJECTDOTHISBYCALLINGTHESTRUCTDESCRIPTORCREATEDESCRIPTORMETHODTHEORACLESQLSTRUCTDESCRIPTORCLASSISSERIALIZABLE,MEANINGTHATYOUCANWRITETHECOMPLETESTATEOFASTRUCTDESCRIPTOROBJECTTOANOUTPUTSTREAMFORLATERUSERECREATETHESTRUCTDESCRIPTOROBJECTBYREADINGITSSERIALIZEDSTATEFROMANINPUTSTREAMTHISISREFERREDTOASDESERIALIZINGWITHTHESTRUCTDESCRIPTOROBJECTSERIALIZED,YOUDONOTNEEDTOCALLTHESTRUCTDESCRIPTORCREATEDESCRIPTORMETHODYOUSIMPLYDESERIALIZETHESTRUCTDESCRIPTOROBJECTITISADVISABLETOSERIALIZEASTRUCTDESCRIPTOROBJECTWHENTHEOBJECTTYPEISCOMPLEXBUTNOTCHANGEDOFTENIFYOUCREATEASTRUCTDESCRIPTOROBJECTTHROUGHDESERIALIZATION,YOUMUSTSUPPLYTHEAPPROPRIATEDATABASECONNECTIONINSTANCEFORTHESTRUCTDESCRIPTOROBJECT,USINGTHESETCONNECTIONMETHODTHEFOLLOWINGCODEPROVIDESTHECONNECTIONINSTANCEFORASTRUCTDESCRIPTOROBJECTPUBLICVOIDSETCONNECTIONCONNECTIONCONNTHROWSSQLEXCEPTIONRETRIEVINGSTRUCTOBJECTSANDATTRIBUTESTHISSECTIONDISCUSSESHOWTORETRIEVEANDMANIPULATEORACLEOBJECTSANDTHEIRATTRIBUTES,USINGEITHERORACLESPECIFICFEATURESORJDBC20STANDARDFEATURESRETRIEVINGANORACLEOBJECTASANORACLESQLSTRUCTOBJECTYOUCANRETRIEVEANORACLEOBJECTDIRECTLYINTOANORACLESQLSTRUCTINSTANCEINTHEFOLLOWINGEXAMPLE,GETOBJECTISUSEDTOGETANUMBEROBJECTFROMCOLUMN1COL1OFTHETABLESTRUCT_TABLEBECAUSEGETOBJECTRETURNSANOBJECTTYPE,THERETURNISCASTTOANORACLESQLSTRUCTTHISEXAMPLEASSUMESTHATTHESTATEMENTOBJECTSTMTHASALREADYBEENCREATEDSTRINGCMDCMD“CREATETYPETYPE_STRUCTASOBJECTFIELD1NUMBER,FIELD2DATE“STMTEXECUTECMDCMD“CREATETABLESTRUCT_TABLECOL1TYPE_STRUCT“STMTEXECUTECMDCMD“INSERTINTOSTRUCT_TABLEVALUESTYPE_STRUCT10,01APR01“STMTEXECUTECMDCMD“INSERTINTOSTRUCT_TABLEVALUESTYPE_STRUCT20,02MAY02“STMTEXECUTECMDRESULTSETRSSTMTEXECUTEQUERY“SELECTFROMSTRUCT_TABLE“ORACLESQLSTRUCTORACLESTRUCTORACLESQLSTRUCTRSGETOBJECT1ANOTHERWAYTORETURNTHEOBJECTASASTRUCTOBJECTISTOCASTTHERESULTSETTOANORACLERESULTSETOBJECTANDUSETHEORACLEEXTENSIONGETSTRUCTMETHODORACLESQLSTRUCTORACLESTRUCTORACLERESULTSETRSGETSTRUCT1RETRIEVINGANORACLEOBJECTASAJAVASQLSTRUCTOBJECTALTERNATIVELY,REFERRINGBACKTOTHEPREVIOUSEXAMPLE,YOUCANUSESTANDARDJDBCFUNCTIONALITYSUCHASGETOBJECTTORETRIEVEANORACLEOBJECTFROMTHEDATABASEASANINSTANCEOFJAVASQLSTRUCTORACLEJDBC2STRUCTUNDERJDK11XBECAUSEGETOBJECTRETURNSAJAVALANGOBJECT,YOUMUSTCASTTHEOUTPUTOFTHEMETHODTOASTRUCTFOREXAMPLERESULTSETRSSTMTEXECUTEQUERY“SELECTFROMSTRUCT_TABLE“JAVASQLSTRUCTJDBCSTRUCTJAVASQLSTRUCTRSGETOBJECT1RETRIEVINGATTRIBUTESASORACLESQLTYPESIFYOUWANTTORETRIEVEORACLEOBJECTATTRIBUTESFROMASTRUCTORSTRUCTINSTANCEASORACLESQLTYPES,USETHEGETORACLEATTRIBUTESMETHODOFTHEORACLESQLSTRUCTCLASSFORASTRUCTINSTANCE,YOUWILLHAVETOCASTTOASTRUCTINSTANCEREFERRINGBACKTOTHEPREVIOUSEXAMPLESORACLESQLDATUMATTRSORACLESTRUCTGETORACLEATTRIBUTESORORACLESQLDATUMATTRSORACLESQLSTRUCTJDBCSTRUCTGETORACLEATTRIBUTESRETRIEVINGATTRIBUTESASSTANDARDJAVATYPESIFYOUWANTTORETRIEVEORACLEOBJECTATTRIBUTESASSTANDARDJAVATYPESFROMASTRUCTORSTRUCTINSTANCE,USETHESTANDARDGETATTRIBUTESMETHODOBJECTATTRSJDBCSTRUCTGETATTRIBUTESBINDINGSTRUCTOBJECTSINTOSTATEMENTSTOBINDANORACLESQLSTRUCTOBJECTTOAPREPAREDSTATEMENTORCALLABLESTATEMENT,YOUCANEITHERUSETHESTANDARDSETOBJECTMETHODSPECIFYINGTHETYPECODE,ORCASTTHESTATEMENTOBJECTTOANORACLESTATEMENTOBJECTANDUSETHEORACLEEXTENSIONSETORACLEOBJECTMETHODFOREXAMPLEPREPAREDSTATEMENTPSCONNPREPARESTATEMENT“TEXT_OF_PREPARED_STATEMENT“STRUCTMYSTRUCTNEWSTRUCTPSSETOBJECT1,MYSTRUCT,TYPESSTRUCT/ORACLETYPESSTRUCTUNDERJDK11XORPREPAREDSTATEMENTPSCONNPREPARESTATEMENT“TEXT_OF_PREPARED_STATEMENT“STRUCTMYSTRUCTNEWSTRUCTORACLEPREPAREDSTATEMENTPSSETORACLEOBJECT1,MYSTRUCTSTRUCTAUTOMATICATTRIBUTEBUFFERINGTHEORACLEJDBCDRIVERFURNISHESPUBLICMETHODSTOENABLEANDDISABLEBUFFERINGOFSTRUCTATTRIBUTESSEE“ARRAYAUTOMATICELEMENTBUFFERING“ONPAGE119FORADISCUSSIONOFHOWTOBUFFERARRAYELEMENTSTHEFOLLOWINGMETHODSAREINCLUDEDWITHTHEORACLESQLSTRUCTCLASSPUBLICVOIDSETAUTOBUFFERINGBOOLEANENABLEPUBLICBOOLEANGETAUTOBUFFERINGTHESETAUTOBUFFERINGBOOLEANMETHODENABLESORDISABLESAUTOBUFFERINGTHEGETAUTOBUFFERINGMETHODRETURNSTHECURRENTAUTOBUFFERINGMODEBYDEFAULT,AUTOBUFFERINGISDISABLEDITISADVISABLETOENABLEAUTOBUFFERINGINAJDBCAPPLICATIONWHENTHESTRUCTATTRIBUTESWILLBEACCESSEDMORETHANONCEBYTHEGETATTRIBUTESANDGETARRAYMETHODSPRESUMINGTHEARRAYDATAISABLETOFITINTOTHEJVMMEMORYWITHOUTOVERFLOWWHENYOUENABLEAUTOBUFFERING,THEORACLESQLSTRUCTOBJECTKEEPSALOCALCOPYOFALLTHECONVERTEDATTRIBUTESTHISDATAISRETAINEDSOTHATASECONDACCESSOFTHISINFORMATIONDOESNOTREQUIREGOINGTHROUGHTHEDATAFORMATCONVERSIONPROCESSCREATINGANDUSINGCUSTOMOBJECTCLASSESFORORACLEOBJECTSIFYOUWANTTOCREATECUSTOMOBJECTCLASSESFORYOURORACLEOBJECTS,THENYOUMUSTDEFINEENTRIESINTHETYPEMAPTHATSPECIFYTHECUSTOMOBJECTCLASSESTHATTHEDRIVERSWILLINSTANTIATEFORTHECORRESPONDINGORACLEOBJECTSYOUMUSTALSOPROVIDEAWAYTOCREATEANDPOPULATEINSTANCESOFTHECUSTOMOBJECTCLASSFROMTHEORACLEOBJECTANDITSATTRIBUTEDATATHEDRIVERMUSTBEABLETOREADFROMACUSTOMOBJECTCLASSANDWRITETOITINADDITION,THECUSTOMOBJECTCLASSCANPROVIDEGETXXXANDSETXXXMETHODSCORRESPONDINGTOTHEORACLEOBJECTSATTRIBUTES,ALTHOUGHTHISISNOTNECESSARYTOCREATEANDPOPULATETHECUSTOMCLASSESANDPROVIDETHESEREAD/WRITECAPABILITIES,YOUCANCHOOSEBETWEENTHESETWOINTERFACESTHEJDBCSTANDARDSQLDATAINTERFACETHEORADATAANDORADATAFACTORYINTERFACESPROVIDEDBYORACLETHECUSTOMOBJECTCLASSYOUCREATEMUSTIMPLEMENTONEOFTHESEINTERFACESTHEORADATAINTERFACECANALSOBEUSEDTOIMPLEMENTTHECUSTOMREFERENCECLASSCORRESPONDINGTOTHECUSTOMOBJECTCLASSIFYOUAREUSINGTHESQLDATAINTERFACE,HOWEVER,YOUCANONLYUSEWEAKREFERENCETYPESINJAVAJAVASQLREFORORACLESQLREFTHESQLDATAINTERFACEISFORMAPPINGSQLOBJECTSONLYASANEXAMPLE,ASSUMEYOUHAVEANORACLEOBJECTTYPE,EMPLOYEE,INTHEDATABASETHATCONSISTSOFTWOATTRIBUTESNAMEWHICHISTYPECHARANDEMPNUMEMPLOYEENUMBER,WHICHISTYPENUMBERYOUUSETHETYPEMAPTOSPECIFYTHATTHEEMPLOYEEOBJECTSHOULDMAPTOACUSTOMOBJECTCLASSTHATYOUCALLJEMPLOYEEYOUCANIMPLEMENTEITHERTHESQLDATAORORADATAINTERFACEINTHEJEMPLOYEECLASSYOUCANCREATECUSTOMOBJECTCLASSESYOURSELF,BUTTHEMOSTCONVENIENTWAYTOCREATETHEMISTOEMPLOYTHEORACLEJPUBLISHERUTILITYTOCREATETHEMFORYOUJPUBLISHERSUPPORTSTHESTANDARDSQLDATAINTERFACEASWELLASTHEORACLESPECIFICORADATAINTERFACE,ANDISABLETOGENERATECLASSESTHATIMPLEMENTEITHERONESEE“USINGJPUBLISHERTOCREATECUSTOMOBJECTCLASSES“ONPAGE945FORMOREINFORMATIONTHEFOLLOWINGSECTIONCOMPARESORADATAANDSQLDATAFUNCTIONALITYRELATIVEADVANTAGESOFORADATAVERSUSSQLDATAINDECIDINGWHICHOFTHESETWOINTERFACEIMPLEMENTATIONSTOUSE,CONSIDERTHEFOLLOWINGADVANTAGESOFORADATAITDOESNOTREQUIREANENTRYINTHETYPEMAPFORTHEORACLEOBJECTITHASAWARENESSOFORACLEEXTENSIONSYOUCANCONSTRUCTAORADATAFROMANORACLESQLSTRUCTTHISISMOREEFFICIENTBECAUSEITAVOIDSUNNECESSARYCONVERSIONSTONATIVEJAVATYPESYOUCANOBTAINTHECORRESPONDINGDATUMOBJECTWHICHISINORACLESQLFORMATFROMTHEORADATAOBJECT,USINGTHETODATUMMETHODITPROVIDESBETTERPERFORMANCEORADATAWORKSDIRECTLYWITHDATUMTYPES,WHICHISTHEINTERNALFORMATUSEDBYTHEDRIVERTOHOLDORACLEOBJECTSADVANTAGESOFSQLDATAITISAJDBCSTANDARD,MAKINGYOURCODEMOREPORTABLETHESQLDATAINTERFACEISFORMAPPINGSQLOBJECTSONLYTHEORADATAINTERFACEISMOREFLEXIBLE,ENABLINGYOUTOMAPSQLOBJECTSASWELLASANYOTHERSQLTYPEFORWHICHYOUWANTTOCUSTOMIZEPROCESSINGYOUCANCREATEAORADATAOBJECTFROMANYDATATYPEFOUNDINANORACLEDATABASETHISCOULDBEUSEFUL,FOREXAMPLE,FORSERIALIZINGRAWDATAINJAVAUNDERSTANDINGTYPEMAPSFORSQLDATAIMPLEMENTATIONSIFYOUUSETHESQLDATAINTERFACEINACUSTOMOBJECTCLASS,THENYOUMUSTCREATETYPEMAPENTRIESTHATSPECIFYTHECUSTOMOBJECTCLASSTOUSEINMAPPINGTHEORACLEOBJECTTYPESQLOBJECTTYPETOJAVAYOUCANEITHERUSETHEDEFAULTTYPEMAPOFTHECONNECTIONOBJECT,ORATYPEMAPTHATYOUSPECIFYWHENYOURETRIEVETHEDATAFROMTHERESULTSETTHERESULTSETINTERFACEGETOBJECTMETHODHASASIGNATURETHATLETSYOUSPECIFYATYPEMAPRSGETOBJECTINTCOLUMNINDEXORRSGETOBJECTINTCOLUMNINDEX,MAPMAPFORADESCRIPTIONOFHOWTOCREATETHESECUSTOMOBJECTCLASSESWITHSQLDATA,SEE“CREATINGANDUSINGCUSTOMOBJECTCLASSESFORORACLEOBJECTS“ONPAGE910WHENUSINGASQLDATAIMPLEMENTATION,IFYOUDONOTINCLUDEATYPEMAPENTRY,THENTHEOBJECTWILLMAPTOTHEORACLESQLSTRUCTCLASSBYDEFAULTORADATAIMPLEMENTATIONS,BYCONTRAST,HAVETHEIROWNMAPPINGFUNCTIONALITYSOTHATATYPEMAPENTRYISNOTREQUIREDWHENUSINGAORADATAIMPLEMENTATION,USETHEORACLEGETORADATAMETHODINSTEADOFTHESTANDARDGETOBJECTMETHODTHETYPEMAPRELATESAJAVACLASSTOTHESQLTYPENAMEOFANORACLEOBJECTTHISONETOONEMAPPINGISSTOREDINAHASHTABLEASAKEYWORDVALUEPAIRWHENYOUREADDATAFROMANORACLEOBJECT,THEJDBCDRIVERCONSIDERSTHETYPEMAPTODETERMINEWHICHJAVACLASSTOUSETOMATERIALIZETHEDATAFROMTHEORACLEOBJECTTYPESQLOBJECTTYPEWHENYOUWRITEDATATOANORACLEOBJECT,THEJDBCDRIVERGETSTHESQLTYPENAMEFROMTHEJAVACLASSBYCALLINGTHEGETSQLTYPENAMEMETHODOFTHESQLDATAINTERFACETHEACTUALCONVERSIONBETWEENSQLANDJAVAISPERFORMEDBYTHEDRIVERTHEATTRIBUTESOFTHEJAVACLASSTHATCORRESPONDSTOANORACLEOBJECTCANUSEEITHERJAVANATIVETYPESORORACLENATIVETYPESINSTANCESOFTHEORACLESQLCLASSESTOSTOREATTRIBUTESCREATINGATYPEMAPOBJECTANDDEFININGMAPPINGSFORASQLDATAIMPLEMENTATIONWHENUSINGASQLDATAIMPLEMENTATION,THEJDBCAPPLICATIONSPROGRAMMERISRESPONSIBLEFORPROVIDINGATYPEMAP,WHICHMUSTBEANINSTANCEOFACLASSASFOLLOWSUNDERJDK12X,ANINSTANCEOFACLASSTHATIMPLEMENTSTHESTANDARDJAVAUTILMAPINTERFACEORUNDERJDK11X,ANINSTANCEOFACLASSTHATEXTENDSTHESTANDARDJAVAUTILDICTIONARYCLASSORANINSTANCEOFTHEDICTIONARYCLASSITSELFYOUHAVETHEOPTIONOFCREATINGYOUROWNCLASSTOACCOMPLISHTHIS,BUTUNDEREITHERJDK12XORJDK11X,THESTANDARDCLASSJAVAUTILHASHTABLEMEETSTHEREQUIREMENT中文翻譯使用ORACLE對象類型這一章說明了JDBC支持用戶定義的對象類型，它討論的是ORACLESQLSTRUCT類的功能，以及如何將它映射到一個實現(xiàn)JDBC標(biāo)準(zhǔn)SQLDATA接口或ORACLEORADATA接口的自定義類。這章還描述了在SQL表示中JDBC驅(qū)動怎樣訪問SQLJ對象類型下面的主題包括映射ORACLE對象對于ORACLE對象使用默認的STRUCT類創(chuàng)建和使用自定義對象類為ORACLE對象對象類型的繼承用JPUBLISHER來創(chuàng)建自定義對象類描述一個對象類型SQLJ對象類型NOTE有關(guān)ORACLE對象功能的一般信息和功能，請參閱ORACLE9I應(yīng)用程序開發(fā)人員指南關(guān)系對象的功能。映射ORACLE對象ORACLE對象類型提供對數(shù)據(jù)庫中的復(fù)合數(shù)據(jù)結(jié)構(gòu)的支持。例如，您可以定義一個類型人員具有屬性，如名稱（類型CHAR，電話號碼（類型CHAR）和雇員編號（類型NUMBER）。同時ORACLE還在ORACLE對象功能和它的JDBC之間間提供緊密地聯(lián)系，可以用一個標(biāo)準(zhǔn)的、泛型JDBC類型來映射到ORACLE對象，或者你可以自定義映射通過創(chuàng)建自定義JAVA類型定義類。在本書中，你創(chuàng)建映射到ORACLE對象的JAVA類會被當(dāng)作自定義JAVA類來訪問或者進一步說是自定義對象類。這就像是自定義引用類映射到對象引用以及自定義集合類映射到ORACLE集合。自定義對象類可以實現(xiàn)標(biāo)準(zhǔn)的JDBC接口或者一個ORACLE擴充接口來讀寫數(shù)據(jù)。JDBC使ORACLE對象作為特定JAVA類的實例化成為了現(xiàn)實。用JDBC訪問ORACLE對象需要2個步驟1）為ORACLE對象創(chuàng)建JAVA類，2）并填充這些類，你有兩個選擇讓JDBC實現(xiàn)結(jié)構(gòu)體類型對象。這在93頁上“使用為ORACLE對象的默認STRUCT類“中說明了。顯式指出ORACLE對象和JAVA類之間的映射。這包括為對象數(shù)據(jù)自定義你的JAVA類。該驅(qū)動程序然后必須能夠填充您指定的自定義對象類的實例。這涉及到一系列JAVA類的約束。為了滿足這些約束，你可以定義你的類去實現(xiàn)JDBC標(biāo)準(zhǔn)JAVASQLSQLDATA接口或ORACLE擴展ORACLESQLORADATA接口。這在910頁上“創(chuàng)建和使用自定義對象類為ORACLE對象“中說明了?？梢允褂肙RACLEJPUBLISHER實用程序以生成自定義JAVA類。NOTE當(dāng)您使用SQLDATA接口時,必須使用一個JAVA類型映射來指定您的SQLJAVA映射，除非弱類型JAVASQLSTRUCT對象滿足。請參閱911頁“了解類型SQLDATA實現(xiàn)映射“。對于ORACLE對象使用默認的STRUCT類如果你不選擇自定義類作為你的SQLJAVA映射ORACLE對象