翻译文献-使用 oracle 对象类型

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中文翻译使用ORACLE对象类型这一章说明了JDBC支持用户定义的对象类型，它讨论的是ORACLESQLSTRUCT类的功能，以及如何将它映射到一个实现JDBC标准SQLDATA接口或ORACLEORADATA接口的自定义类。这章还描述了在SQL表示中JDBC驱动怎样访问SQLJ对象类型下面的主题包括映射ORACLE对象对于ORACLE对象使用默认的STRUCT类创建和使用自定义对象类为ORACLE对象对象类型的继承用JPUBLISHER来创建自定义对象类描述一个对象类型SQLJ对象类型NOTE有关ORACLE对象功能的一般信息和功能，请参阅ORACLE9I应用程序开发人员指南关系对象的功能。映射ORACLE对象ORACLE对象类型提供对数据库中的复合数据结构的支持。例如，您可以定义一个类型人员具有属性，如名称（类型CHAR，电话号码（类型CHAR）和雇员编号（类型NUMBER）。同时ORACLE还在ORACLE对象功能和它的JDBC之间间提供紧密地联系，可以用一个标准的、泛型JDBC类型来映射到ORACLE对象，或者你可以自定义映射通过创建自定义JAVA类型定义类。在本书中，你创建映射到ORACLE对象的JAVA类会被当作自定义JAVA类来访问或者进一步说是自定义对象类。这就像是自定义引用类映射到对象引用以及自定义集合类映射到ORACLE集合。自定义对象类可以实现标准的JDBC接口或者一个ORACLE扩充接口来读写数据。JDBC使ORACLE对象作为特定JAVA类的实例化成为了现实。用JDBC访问ORACLE对象需要2个步骤1）为ORACLE对象创建JAVA类，2）并填充这些类，你有两个选择让JDBC实现结构体类型对象。这在93页上“使用为ORACLE对象的默认STRUCT类“中说明了。显式指出ORACLE对象和JAVA类之间的映射。这包括为对象数据自定义你的JAVA类。该驱动程序然后必须能够填充您指定的自定义对象类的实例。这涉及到一系列JAVA类的约束。为了满足这些约束，你可以定义你的类去实现JDBC标准JAVASQLSQLDATA接口或ORACLE扩展ORACLESQLORADATA接口。这在910页上“创建和使用自定义对象类为ORACLE对象“中说明了。可以使用ORACLEJPUBLISHER实用程序以生成自定义JAVA类。NOTE当您使用SQLDATA接口时,必须使用一个JAVA类型映射来指定您的SQLJAVA映射，除非弱类型JAVASQLSTRUCT对象满足。请参阅911页“了解类型SQLDATA实现映射“。对于ORACLE对象使用默认的STRUCT类如果你不选择自定义类作为你的SQLJAVA映射ORACLE对象