用SpringBoot整合Mybatis的时候出了状况。
Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled. 2019-08-15 10:06:57.108 ERROR 12712 --- [ restartedMain] o.s.boot.SpringApplication : Application run failed org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'userMapper' defined in file [D:\EclipseWorkspace\online_video\target\classes\edu\hpu\mapper\UserMapper.class]: Invocation of init method failed; nested exception is java.lang.IllegalArgumentException: org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. Cause: java.lang.IllegalArgumentException: Result Maps collection already contains value for edu.hpu.mapper.UserMapper.BaseResultMap at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1778) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE] at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:593) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE] at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE] at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE] at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE] at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE] at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE] at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:826) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE] at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:877) ~[spring-context-5.1.9.RELEASE.jar:5.1.9.RELEASE] at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:549) ~[spring-context-5.1.9.RELEASE.jar:5.1.9.RELEASE] at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141) ~[spring-boot-2.1.7.RELEASE.jar:2.1.7.RELEASE] at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:743) [spring-boot-2.1.7.RELEASE.jar:2.1.7.RELEASE] at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:390) [spring-boot-2.1.7.RELEASE.jar:2.1.7.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:312) [spring-boot-2.1.7.RELEASE.jar:2.1.7.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1214) [spring-boot-2.1.7.RELEASE.jar:2.1.7.RELEASE] at org.springframework.boot.SpringApplication.run(SpringApplication.java:1203) [spring-boot-2.1.7.RELEASE.jar:2.1.7.RELEASE] at edu.hpu.OnlineVideoApplication.main(OnlineVideoApplication.java:12) [classes/:na] at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_144] at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_144] at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_144] at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_144] at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) [spring-boot-devtools-2.1.7.RELEASE.jar:2.1.7.RELEASE] Caused by: java.lang.IllegalArgumentException: org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. Cause: java.lang.IllegalArgumentException: Result Maps collection already contains value for edu.hpu.mapper.UserMapper.BaseResultMap at org.mybatis.spring.mapper.MapperFactoryBean.checkDaoConfig(MapperFactoryBean.java:84) ~[mybatis-spring-1.3.0.jar:1.3.0] at org.springframework.dao.support.DaoSupport.afterPropertiesSet(DaoSupport.java:44) ~[spring-tx-5.1.9.RELEASE.jar:5.1.9.RELEASE] at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1837) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE] at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1774) ~[spring-beans-5.1.9.RELEASE.jar:5.1.9.RELEASE] ... 21 common frames omitted Caused by: org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. Cause: java.lang.IllegalArgumentException: Result Maps collection already contains value for edu.hpu.mapper.UserMapper.BaseResultMap at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:120) ~[mybatis-3.4.0.jar:3.4.0] at org.apache.ibatis.builder.xml.XMLMapperBuilder.parse(XMLMapperBuilder.java:92) ~[mybatis-3.4.0.jar:3.4.0] at org.apache.ibatis.builder.annotation.MapperAnnotationBuilder.loadXmlResource(MapperAnnotationBuilder.java:169) ~[mybatis-3.4.0.jar:3.4.0] at org.apache.ibatis.builder.annotation.MapperAnnotationBuilder.parse(MapperAnnotationBuilder.java:120) ~[mybatis-3.4.0.jar:3.4.0] at org.apache.ibatis.binding.MapperRegistry.addMapper(MapperRegistry.java:72) ~[mybatis-3.4.0.jar:3.4.0] at org.apache.ibatis.session.Configuration.addMapper(Configuration.java:706) ~[mybatis-3.4.0.jar:3.4.0] at org.mybatis.spring.mapper.MapperFactoryBean.checkDaoConfig(MapperFactoryBean.java:81) ~[mybatis-spring-1.3.0.jar:1.3.0] ... 24 common frames omitted Caused by: java.lang.IllegalArgumentException: Result Maps collection already contains value for edu.hpu.mapper.UserMapper.BaseResultMap at org.apache.ibatis.session.Configuration$StrictMap.put(Configuration.java:837) ~[mybatis-3.4.0.jar:3.4.0] at org.apache.ibatis.session.Configuration$StrictMap.put(Configuration.java:809) ~[mybatis-3.4.0.jar:3.4.0] at org.apache.ibatis.session.Configuration.addResultMap(Configuration.java:591) ~[mybatis-3.4.0.jar:3.4.0] at org.apache.ibatis.builder.MapperBuilderAssistant.addResultMap(MapperBuilderAssistant.java:214) ~[mybatis-3.4.0.jar:3.4.0] at org.apache.ibatis.builder.ResultMapResolver.resolve(ResultMapResolver.java:47) ~[mybatis-3.4.0.jar:3.4.0] at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElement(XMLMapperBuilder.java:285) ~[mybatis-3.4.0.jar:3.4.0] at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElement(XMLMapperBuilder.java:252) ~[mybatis-3.4.0.jar:3.4.0] at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElements(XMLMapperBuilder.java:244) ~[mybatis-3.4.0.jar:3.4.0] at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:116) ~[mybatis-3.4.0.jar:3.4.0] ... 30 common frames omitted
这个问题出在哪儿，我的mappe接口和映射文件都是用Mybatis逆向工具生成的，不止运行了一次，Mybatis Gernerator默认是采用追加的方式，所以UserMapper.xml中有了许多重复的内容，把重复的内容删掉，然后maven clean，重新启动。
怎么设置Mybatis Gernerator非追加的方式呢，查到一篇博客，没有实践，先留个地址。【2】
参考：
【1】、http://ju.outofmemory.cn/entry/145159
【2】、https://www.cnblogs.com/wulm/p/9860726.html
