异常：java.lang.IllegalArgumentException: Result Maps collection already contains ...

贴一个困扰了一下午的异常，异常信息如下：

十一月 24, 2017 9:26:07 上午 org.apache.catalina.core.ApplicationContext log严重: StandardWrapper.Throwableorg.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sqlSessionFactory' defined in file [F:\JavaWeb\.metadata\.plugins\org.eclipse.wst.server.core\tmp1\wtpwebapps\jh_qisf\WEB-INF\classes\spring\spring-dao.xml]: Invocation of init method failed; nested exception is org.springframework.core.NestedIOException: Failed to parse mapping resource: 'file [F:\JavaWeb\.metadata\.plugins\org.eclipse.wst.server.core\tmp1\wtpwebapps\jh_qisf\WEB-INF\classes\mapper\DepartmentMapper.xml]'; nested exception is org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. Cause: java.lang.IllegalArgumentException: Result Maps collection already contains value for cn.jinhai.qisf.dao.DepartmentMapper.BaseResultMapat org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1574)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:539)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476)at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:303)at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299)at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:736)at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:757)at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480)at org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:664)at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:630)at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:678)at org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:549)at org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:490)at org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:136)at javax.servlet.GenericServlet.init(GenericServlet.java:158)at org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1269)at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1182)at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:853)at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:134)at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:110)at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:506)at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:962)at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:445)at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1115)at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)at java.lang.Thread.run(Thread.java:748)Caused by: org.springframework.core.NestedIOException: Failed to parse mapping resource: 'file [F:\JavaWeb\.metadata\.plugins\org.eclipse.wst.server.core\tmp1\wtpwebapps\jh_qisf\WEB-INF\classes\mapper\DepartmentMapper.xml]'; nested exception is org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. Cause: java.lang.IllegalArgumentException: Result Maps collection already contains value for cn.jinhai.qisf.dao.DepartmentMapper.BaseResultMapat org.mybatis.spring.SqlSessionFactoryBean.buildSqlSessionFactory(SqlSessionFactoryBean.java:468)at org.mybatis.spring.SqlSessionFactoryBean.afterPropertiesSet(SqlSessionFactoryBean.java:343)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1633)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1570)... 34 moreCaused by: org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. Cause: java.lang.IllegalArgumentException: Result Maps collection already contains value for cn.jinhai.qisf.dao.DepartmentMapper.BaseResultMapat org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:120)at org.apache.ibatis.builder.xml.XMLMapperBuilder.parse(XMLMapperBuilder.java:92)at org.mybatis.spring.SqlSessionFactoryBean.buildSqlSessionFactory(SqlSessionFactoryBean.java:466)... 37 moreCaused by: java.lang.IllegalArgumentException: Result Maps collection already contains value for cn.jinhai.qisf.dao.DepartmentMapper.BaseResultMapat org.apache.ibatis.session.Configuration$StrictMap.put(Configuration.java:802)at org.apache.ibatis.session.Configuration$StrictMap.put(Configuration.java:774)at org.apache.ibatis.session.Configuration.addResultMap(Configuration.java:556)at org.apache.ibatis.builder.MapperBuilderAssistant.addResultMap(MapperBuilderAssistant.java:217)at org.apache.ibatis.builder.ResultMapResolver.resolve(ResultMapResolver.java:47)at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElement(XMLMapperBuilder.java:285)at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElement(XMLMapperBuilder.java:252)at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElements(XMLMapperBuilder.java:244)at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:116)... 39 more十一月 24, 2017 9:26:07 上午 org.apache.catalina.core.StandardWrapperValve invoke严重: Allocate exception for servlet mvc-dispatcherjava.lang.IllegalArgumentException: Result Maps collection already contains value for cn.jinhai.qisf.dao.DepartmentMapper.BaseResultMapat org.apache.ibatis.session.Configuration$StrictMap.put(Configuration.java:802)at org.apache.ibatis.session.Configuration$StrictMap.put(Configuration.java:774)at org.apache.ibatis.session.Configuration.addResultMap(Configuration.java:556)at org.apache.ibatis.builder.MapperBuilderAssistant.addResultMap(MapperBuilderAssistant.java:217)at org.apache.ibatis.builder.ResultMapResolver.resolve(ResultMapResolver.java:47)at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElement(XMLMapperBuilder.java:285)at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElement(XMLMapperBuilder.java:252)at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElements(XMLMapperBuilder.java:244)at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:116)at org.apache.ibatis.builder.xml.XMLMapperBuilder.parse(XMLMapperBuilder.java:92)at org.mybatis.spring.SqlSessionFactoryBean.buildSqlSessionFactory(SqlSessionFactoryBean.java:466)at org.mybatis.spring.SqlSessionFactoryBean.afterPropertiesSet(SqlSessionFactoryBean.java:343)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1633)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1570)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:539)at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476)at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:303)at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299)at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:736)at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:757)at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480)at org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:664)at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:630)at org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:678)at org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:549)at org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:490)at org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:136)at javax.servlet.GenericServlet.init(GenericServlet.java:158)at org.apache.catalina.core.StandardWrapper.initServlet(StandardWrapper.java:1269)at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1182)at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:853)at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:134)at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:110)at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:506)at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:962)at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:445)at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1115)at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)at java.lang.Thread.run(Thread.java:748)

该异常大概的展现方式如下：

java.lang.IllegalArgumentException: Result Maps collection already contains value for xxx.xxx.xxx.BaseResultMap

意思大概是已经存在这个结果集，花费了好多时间找这个问题的原因，最后用eclipse的全局搜索发现，确实在同一个mapper文件下存在重复的BaseResultMap。
这个问题的产生原因是：使用mybatis逆向工程多次生成mapper时，未将之前生成的mapper.xml删除，导致其在原有的xml里追加内容。最终导致BaseResultMap重复。
解决方法：删除已生成的mapper.xml，重新生成。