xm/src/main/resources/mapper/MessagesMapper.xml

<?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.zhentao.mapper.MessagesMapper">

    <resultMap id="BaseResultMap" type="com.zhentao.pojo.Messages">
            <id property="messageId" column="message_id" jdbcType="BIGINT"/>
            <result property="userId" column="user_id" jdbcType="BIGINT"/>
            <result property="content" column="content" jdbcType="VARCHAR"/>
            <result property="isRead" column="is_read" jdbcType="TINYINT"/>
            <result property="createdAt" column="created_at" jdbcType="TIMESTAMP"/>
    </resultMap>

    <sql id="Base_Column_List">
        message_id,user_id,content,
        is_read,created_at
    </sql>
</mapper>