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

曾经终败给现在 2022-03-17 12:12 175阅读 0赞

今天在测试mybatis接口的时候出现一个异常，花费了不少时间解决了，特此将问题记录下来，希望能帮助更多的同学。

### 异常信息 ###

java.lang.IllegalStateException: Failed to load ApplicationContext
    Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.apache.ibatis.session.SqlSessionFactory]: Factory method 'sqlSessionFactory' threw exception; nested exception is org.springframework.core.NestedIOException: Failed to parse mapping resource: 'file [H:\User\Administrator\IntelliJProjects\SpringBootProject\codegen-java\codegen-dao\target\classes\mappers\TGenResultTemplatePropMapper.xml]'; nested exception is org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. Cause: java.lang.IllegalArgumentException: Result Maps collection already contains value for com.codegen.dao.TGenResultTemplatePropMapper.BaseResultMap
    	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185)
    	at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:582)
    	... 78 more
    Caused by: org.springframework.core.NestedIOException: Failed to parse mapping resource: 'file [H:\User\Administrator\IntelliJProjects\SpringBootProject\codegen-java\codegen-dao\target\classes\mappers\TGenResultTemplatePropMapper.xml]'; nested exception is org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. Cause: java.lang.IllegalArgumentException: Result Maps collection already contains value for com.codegen.dao.TGenResultTemplatePropMapper.BaseResultMap
    	at org.mybatis.spring.SqlSessionFactoryBean.buildSqlSessionFactory(SqlSessionFactoryBean.java:523)
    	at org.mybatis.spring.SqlSessionFactoryBean.afterPropertiesSet(SqlSessionFactoryBean.java:380)
    	at org.mybatis.spring.SqlSessionFactoryBean.getObject(SqlSessionFactoryBean.java:547)
    	at org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration.sqlSessionFactory(MybatisAutoConfiguration.java:153)
    	at org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration$$EnhancerBySpringCGLIB$$67009919.CGLIB$sqlSessionFactory$0(<generated>)
    	at org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration$$EnhancerBySpringCGLIB$$67009919$$FastClassBySpringCGLIB$$6a893377.invoke(<generated>)
    	at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:228)
    	at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:361)
    	at org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration$$EnhancerBySpringCGLIB$$67009919.sqlSessionFactory(<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)
    	... 79 more
    Caused by: org.apache.ibatis.builder.BuilderException: Error parsing Mapper XML. Cause: java.lang.IllegalArgumentException: Result Maps collection already contains value for com.codegen.dao.TGenResultTemplatePropMapper.BaseResultMap
    	at 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:521)
    	... 92 more
    Caused by: java.lang.IllegalArgumentException: Result Maps collection already contains value for com.codegen.dao.TGenResultTemplatePropMapper.BaseResultMap
    	at org.apache.ibatis.session.Configuration$StrictMap.put(Configuration.java:859)
    	at org.apache.ibatis.session.Configuration$StrictMap.put(Configuration.java:831)
    	at org.apache.ibatis.session.Configuration.addResultMap(Configuration.java:613)
    	at org.apache.ibatis.builder.MapperBuilderAssistant.addResultMap(MapperBuilderAssistant.java:214)
    	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)
    	... 94 more

### 原因 ###

找到核心异常

Caused by: java.lang.IllegalArgumentException: Result Maps collection already contains value for com.codegen.dao.TGenResultTemplatePropMapper.BaseResultMap

是`BaseResultMap`出了问题，这个mapper.xml都是自动生成的怎么会有问题，原因是因为 `BaseResultMap`这个结果出现了多次。也就是有两个 id 为 `BaseResultMap`。

### 解决办法 ###

最后找到报错的 mapper.xml 文件 搜索`BaseResultMap` 这个关键字，果然出现了两次 `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里面追加内容。最终导致 `BaseResultMap` 重复。删除已生成的 mapper.xml 文件， 重新生成即可。

#### 总结 ####

**`mapper.xml`里面不能有同样的id名，否则就会报上面类似的异常** 。

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