数据库配置文件.db(放在resource下)：

Mb.driver = com.mysql.cj.jdbc.Driver
Mb.url = jdbc:mysql://127.0.0.1:3306/数据库名
Mb.username = root
Mb.password = 密码

mybatis-config的xml文件（放在resource下）：

<?xml version="1.0" encoding="UTF-8" ?>
<!--mybatis约束-->
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!--    连接数据库环境-->
    <properties resource="数据库配置文件路径"></properties>
<!--    驼峰映射开启-->
    <settings>
        <setting name="mapUnderscoureToCamelCase" value="true"/>
    </settings>
    <!--    设置别名，以类名为别-->
    <typeAliases>
        <package name=""/>
    </typeAliases>
    <environments default="mybatis">
        <environment id="mybatis">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${Mb.driver}"/>
                <property name="url" value="${Mb.url}"/>
                <property name="username" value="${Mb.username}"/>
                <property name="password" value="${Mb.password}"/>
            </dataSource>
        </environment>
    </environments>
    <!--    引入映射文件-->
    <mappers>
        <mapper resource="mapper路径"></mapper>
    </mappers>
</configuration>

Mapper：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.dt.dao.UserMapper">

<!--    <insert id="">-->
<!--     -->
<!--    </insert>-->

<!--    <update id="">-->
<!--    -->
<!--    </update>-->

<!--    <delete id="">-->
<!--      -->
<!--    </delete>-->

<!--  resultType 返回值类型-->
    <select id="mapper里的函数名" resultType="实体类（全路径名）">
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    </select>
</mapper>

创建Mapper：

public interface XxxMapper {

    类型 xxx();
}

使用：

String resource = "mybaits-config.xml";//加载配置文件
 InputStream inputStream = Resources.getResourceAsStream(resource);
 SqlSessionFactory sqlSessionFactory  = new SqlSessionFactoryBuilder().build(inputStream);
       SqlSession sqlSession=  sqlSessionFactory.openSession();
       XxxrMapper xxMapper = sqlSession.getMapper(XxxMapper（接口）.class);
       xxMapper.接口里面的方法();