ruoyi-system/src/main/resources/mapper/system/SysUserMessageMapper.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.ruoyi.system.mapper.SysUserMessageMapper">
    <resultMap id="SysUserMessageMap" type="com.ruoyi.system.domain.SysUserMessage">
        <id property="messageId" column="message_id"/>
        <result property="senderId" column="sender_id"/>
        <result property="receiverId" column="receiver_id"/>
        <result property="content" column="content"/>
        <result property="createTime" column="create_time"/>
    </resultMap>

    <insert id="insertMessage" parameterType="com.ruoyi.system.domain.SysUserMessage">
        insert into sys_user_message (sender_id, receiver_id, content, create_time)
        values (#{senderId}, #{receiverId}, #{content}, sysdate())
    </insert>

    <select id="selectMessageListByUserIds" resultMap="SysUserMessageMap">
        select message_id, sender_id, receiver_id, content, create_time
        from sys_user_message
        where (sender_id = #{userId1} and receiver_id = #{userId2})
           or (sender_id = #{userId2} and receiver_id = #{userId1})
            and del_flag = '0'
        order by create_time asc
    </select>

    <select id="selectChatUserIds" parameterType="java.lang.Long" resultType="map">
        SELECT DISTINCT
            CASE
                WHEN m.sender_id = #{userId} THEN m.receiver_id
                ELSE m.sender_id
                END AS userId,
            u.nick_name AS nickName
        FROM sys_user_message m
                 INNER JOIN sys_user u
                            ON (m.sender_id = #{userId} AND m.receiver_id = u.user_id)
                                OR (m.receiver_id = #{userId} AND m.sender_id = u.user_id)
        WHERE (m.sender_id = #{userId} OR m.receiver_id = #{userId})
          AND m.del_flag = '0'
          AND u.del_flag = '0'
        ORDER BY u.nick_name
    </select>
</mapper>