一、问题描述
IDEA下Mybatis启动莫名其妙的报错：
org.springframework.core.NestedIOException: Failed to parse mapping resource: 'file [D:\idea_work\2021-04-06\xxxx\test-web\target\classes\mapper\demo\ExampleAsyncTreeMapper.xml]'; nested exception is org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'file [D:\idea_work\2021-04-06\xxxx\test-web\target\classes\mapper\demo\ExampleAsyncTreeMapper.xml]'. Cause: java.lang.IllegalArgumentException: Result Maps collection already contains value for com.xxxx.web.test.mapper.ExampleAsyncTreeMapper.ExampleAsyncTreeResult
at com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean.buildSqlSessionFactory(MybatisSqlSessionFactoryBean.java:595)
at com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean.afterPropertiesSet(MybatisSqlSessionFactoryBean.java:431)
at com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean.getObject(MybatisSqlSessionFactoryBean.java:628)
at com.xxxx.common.db.collector.SqlSessionFactoryCreator.createSqlSessionFactory(SqlSessionFactoryCreator.java:274)
at com.xxxx.common.core.config.SqlSessionFactoryConfig.sqlSessionFactoryPrimary(SqlSessionFactoryConfig.java:46)
at com.xxxx.common.core.config.SqlSessionFactoryConfig$$EnhancerBySpringCGLIB$$916ae73.CGLIB$sqlSessionFactoryPrimary$0(<generated>)
at com.xxxx.common.core.config.SqlSessionFactoryConfig$$EnhancerBySpringCGLIB$$916ae73$$testClassBySpringCGLIB$$e60ba3c6.invoke(<generated>)
at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:244)
at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:331)
at com.xxxx.common.core.config.SqlSessionFactoryConfig$$EnhancerBySpringCGLIB$$916ae73.sqlSessionFactoryPrimary(<generated>)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154)
at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:650)
at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:635)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1336)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1176)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:556)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1307)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1227)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireByType(AbstractAutowireCapableBeanFactory.java:1509)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1404)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:593)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1307)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1227)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:640)
at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:130)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:399)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1420)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:593)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:897)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:879)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:551)
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141)
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747)
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:315)
at com.xxxx.testApplication.main(testApplication.java:38)
Caused by: org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. The XML location is 'file [D:\idea_work\2021-04-06\xxxx\test-web\target\classes\mapper\demo\ExampleAsyncTreeMapper.xml]'. Cause: java.lang.IllegalArgumentException: Result Maps collection already contains value for com.xxxx.web.test.mapper.ExampleAsyncTreeMapper.ExampleAsyncTreeResult
at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:123)
at org.apache.ibatis.builder.xml.XMLMapperBuilder.parse(XMLMapperBuilder.java:95)
at com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean.buildSqlSessionFactory(MybatisSqlSessionFactoryBean.java:593)
... 56 common frames omitted
Caused by: java.lang.IllegalArgumentException: Result Maps collection already contains value for com.xxxx.web.test.mapper.ExampleAsyncTreeMapper.ExampleAsyncTreeResult
at com.baomidou.mybatisplus.core.MybatisConfiguration$StrictMap.put(MybatisConfiguration.java:429)
at com.baomidou.mybatisplus.core.MybatisConfiguration$StrictMap.put(MybatisConfiguration.java:399)
at com.baomidou.mybatisplus.core.MybatisConfiguration.addResultMap(MybatisConfiguration.java:253)
at org.apache.ibatis.builder.MapperBuilderAssistant.addResultMap(MapperBuilderAssistant.java:209)
at org.apache.ibatis.builder.ResultMapResolver.resolve(ResultMapResolver.java:47)
at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElement(XMLMapperBuilder.java:289)
at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElement(XMLMapperBuilder.java:254)
at org.apache.ibatis.builder.xml.XMLMapperBuilder.resultMapElements(XMLMapperBuilder.java:246)
at org.apache.ibatis.builder.xml.XMLMapperBuilder.configurationElement(XMLMapperBuilder.java:119)
... 58 common frames omitted其中返回的错误信息：Caused by: java.lang.IllegalArgumentException: Result Maps collection already contains value for 已经说明了，存在重复的！
二、解决方法
全局搜索该类，确实有两个，删除无关的一个就行了！或者清空，重新编译一下
