mybatis想打开驼峰命名映射，但总提示无法识别mapUnderscoreToCamelCase

** 错误提示： **

### Error building SqlSession.

The error may exist in SQL Mapper Configuration

Cause: org.apache.ibatis.builder.BuilderException: Error parsing SQL Mapper Configuration. Cause: org.apache.ibatis.builder.BuilderException: The setting mapUnderscoreToCamelCase is not known. Make sure you spelled it correctly (case sensitive).

at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:8)
at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:32)
at org.apache.ibatis.session.SqlSessionFactoryBuilder.build(SqlSessionFactoryBuilder.java:16)

** mybatis配置文件：**

<?xml version="1.0" encoding="UTF-8"?>

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

   <settings> 
      <setting name="mapUnderscoreToCamelCase" value="true" /> 
 </settings>  
<typeAliases>
    <typeAlias alias="OrdersEntity" type="com.jeecg.order.entity.OrdersEntity" />

</typeAliases>
<environments default="development">
    <environment id="development">
        <transactionManager type="JDBC" />
        <dataSource type="POOLED">
            <property name="driver" value="com.mysql.jdbc.Driver" />
            <property name="url"
                value="jdbc:mysql://127.0.0.1:3306/dbname?serverTimezone=UTC" />
            <property name="username" value="dbuser" />
            <property name="password" value="mima" />
        </dataSource>
    </environment>
</environments>
<mappers>

    <mapper resource="ems/mapper/order.xml"></mapper>
        <mapper resource="ems/mapper/ExpressOrder.xml"></mapper>
            <mapper resource="ems/mapper/OrdersEntityMapper.xml"></mapper>
</mappers>

从别处看到过一个相同的，你看下是否有重复的sql。
https://bbs.csdn.net/topics/392313946

应该是mapper.xml里面有错吧

个人建议：千万别用驼峰自动映射，还是老老实实自己给每个字段as，否则后期有可能出现迷之错误。。。。。