在springboot项目中配置数据库下划线命名映射为java的驼峰命名时出错

问题

在使用spirngboot集成mybaits的时候，想要开启命名映射，如图配置

# mybatis配置
mybatis:
  type-aliases-package: com.zhong.springcloud.pojo
  config-location: classpath:mybatis/mybatis-config.xml
  mapper-locations: classpath:mybatis/mapper/*.xml
#  命名映射
  configuration:
    map-underscore-to-camel-case: true

项目中配置了mybatis-config.xml

mybatis-config.xml文件中的配置

DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>
    <settings>
        
        <setting name="cacheEnabled" value="true"/>
    settings>
configuration>

错误信息

Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.apache.ibatis.session.SqlSessionFactory]: Factory method ‘sqlSessionFactory’ threw exception; nested exception is java.lang.IllegalStateException: Property ‘configuration’ and ‘configLocation’ can not specified with together
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:185) ~[spring-beans-5.3.24.jar:5.3.24]
at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:653) ~[spring-beans-5.3.24.jar:5.3.24]
… 78 common frames omitted
Caused by: java.lang.IllegalStateException: Property ‘configuration’ and ‘configLocation’ can not specified with together
at org.springframework.util.Assert.state(Assert.java:76) ~[spring-core-5.3.24.jar:5.3.24]
at org.mybatis.spring.SqlSessionFactoryBean.afterPropertiesSet(SqlSessionFactoryBean.java:488) ~[mybatis-spring-2.0.7.jar:2.0.7]
at org.mybatis.spring.SqlSessionFactoryBean.getObject(SqlSessionFactoryBean.java:633) ~[mybatis-spring-2.0.7.jar:2.0.7]
at org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration.sqlSessionFactory(MybatisAutoConfiguration.java:188) ~[mybatis-spring-boot-autoconfigure-2.2.2.jar:2.2.2]
at org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration$$EnhancerBySpringCGLIB$$36ad62da.CGLIB$sqlSessionFactory$1(<generated>)[mybatis-spring-boot-autoconfigure-\mathrm{2.2.2.}jar:\mathrm{2.2.2}]atorg.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration$$EnhancerBySpringCGLIB$$36ad62da$$FastClassBySpringCGLIB$$54783d2d.invoke(<generated>)[mybatis-spring-boot-autoconfigure-\mathrm{2.2.2.}jar:\mathrm{2.2.2}]atorg.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:244)[spring-core-\mathrm{5.3.24.}jar:\mathrm{5.3.24}]atorg.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:331) ~[spring-context-5.3.24.jar:5.3.24]
at org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration$$EnhancerBySpringCGLIB$$36ad62da.sqlSessionFactory() ~[mybatis-spring-boot-autoconfigure-2.2.2.jar:2.2.2]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_271]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_271]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_271]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_271]
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154) ~[spring-beans-5.3.24.jar:5.3.24]
… 79 common frames omitted

关闭命名映射之后或者关闭配置路径之后项目正常。

原因分析

根据错误信息分析，出现该错误的原因是同时使用了configLocation和configuration属性。这两个属性是SqlSessionFactoryBean类的属性，分别用于指定MyBatis配置文件的位置和MyBatis配置对象。

在配置中，你在application.xml中指定了configLocation属性，在mybatis-config.xml中定义了MyBatis的配置对象，在applicaiton中又指定了configuration属性，因此出现了冲突。

解决方法

1. 解决该问题的方法是，需要在应用程序中删除configLocation属性，只使用applicaiton.yml中的configuration属性来指定MyBatis的配置对象。或者不使用applicaiton.yml中的configuration属性，就可以配置config-locations并且在其中配置属性
2. 如果需要同时启用这两个属性，则需要自定义一个MybatisConfig类，该类将扩展org.mybatis.spring.boot.autoconfigure.MybatisProperties类。