新建类

import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.wrapper.MapWrapper;

import java.util.Map;

/**
 * 将Map的key全部转换为小写
 * */
public class MapKeyLowerWrapper extends MapWrapper {

    public MapKeyLowerWrapper(MetaObject metaObject, Map<String, Object> map) {
        super(metaObject, map);
    }
    @Override
    public String findProperty(String name, boolean useCamelCaseMapping) {
        return name==null?"":name.toLowerCase() ;
    }
}

import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.wrapper.ObjectWrapper;
import org.apache.ibatis.reflection.wrapper.ObjectWrapperFactory;

import java.util.Map;


public class MapWrapperFactory implements ObjectWrapperFactory {

    @Override
    public boolean hasWrapperFor(Object object) {
        return object != null && object instanceof Map;
    }

    @Override
    public ObjectWrapper getWrapperFor(MetaObject metaObject, Object object) {
        return new MapKeyLowerWrapper(metaObject, (Map) object);
    }
}

xml 配置

<bean id="wrapperFactory" class="com.demo.config.MapWrapperFactory">
</bean>

<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource" />
        <!-- 自动扫描mapping.xml文件 -->
        <property name="mapperLocations" value="classpath:com/test/mybatis/mapper/*.xml"></property>
        <property name="objectWrapperFactory" ref="wrapperFactory"></property>
</bean>