spring中mapper层是什么意思？
mapper层的作用是对数据库进行数据持久化操作，他的方法语句是直接针对数据库操作的现在用mybatis逆向工程生成的。mapper层，其实就是dao层，主要是做数据持久层的工作，负责与数据库进行联络的一些任务都封装在此。...
System.getProperty()
System类来自于这个包：java.lang.SystemSystem.getProperty("XXX")方法用来读取JVM中的系统属性，那么java虚拟机中的系统属性使用在运行java程序的时候java-D配置，有两种方式1-在命令行配置在eclipse中，选中这个项目，然后在工具栏中选择ru...
ORA-32486: unsupported operation in recursive branch of recursive WITH clause
文档解释ORA-32486:unsupportedoperationinrecursivebranchofrecursiveWITHclauseCause:TherecursivecomponentoftheUNIONALLinarecursiveWITHclauseelementusedanoperationthat...
ORA-28385: cannot perform a PKI certificate-based migration
文档解释ORA-28385:cannotperformaPKIcertificate-basedmigrationCause:APKIcertificate-basedmigrationtoHSMwasattempted.Action:PerformasymmetricMasterKeymigration.ORA-28...
ORA-30996: Streams operations over non-existent stream
文档解释ORA-30996:Streamsoperationsovernon-existentstreamCause:ThestreampassedisNULLorinvalid.Action:Checktheinputparameters.OTRA-30996:Streamsoperationsovernon-exi...
ORA-41630: invalid value for “string” attribute in the rule class properties
文档解释ORA-41630:invalidvaluefor“string”attributeintheruleclasspropertiesCause:Aninvalidvaluewasspecifiedforanattributeintheruleclassproperties.Action:...