mapper文件

<?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.hspedu.springboot.mybatis.mapper.MonsterMapper">

    <resultMap id="ReservationResultMap" type="Reservation">
        <id property="reservationId" column="reservation_Id" />
        <result property="startTime" column="start_time" />
        <result property="endTime" column="end_time" />
        <result property="topic" column="topic" />
        <association property="room" column="room_id" javaType="Room" select="com.hspedu.springboot.mybatis.mapper.RoomMapper.selectByRoomId" />
        <association property="user" column="user_id" javaType="User" select="com.hspedu.springboot.mybatis.mapper.UserMapper.selectByUserId" />
    </resultMap>

    <insert id="insertReservation" parameterType="Reservation">
        INSERT INTO reservations (room_id, user_id, start_time, end_time, topic)
        VALUES (#{roomId}, #{userId}, #{startTime}, #{endTime}, #{topic})
        <selectKey keyProperty="reservationId" resultType="int" order="AFTER">
            SELECT LAST_INSERT_ID()
        </selectKey>
    </insert>

    <delete id="deleteReservation" parameterType="int">
        DELETE FROM reservations WHERE reservation_id = #{reservationId}
    </delete>

    <select id="selectReservation" resultMap="ReservationResultMap" parameterType="int">
        SELECT *
        FROM reservations
        WHERE reservation_id = #{reservationId}
    </select>

    <select id="selectAllReservations" resultMap="ReservationResultMap">
        SELECT *
        FROM reservations
    </select>

    <update id="updateReservation" parameterType="Reservation">
        UPDATE reservations
        SET room_id = #{roomId},
        user_id = #{userId},
        start_time = #{startTime},
        end_time = #{endTime},
        topic = #{topic}
        WHERE reservation_id = #{reservationId}
    </update>

    <select id="selectReservationsByTimeRange" resultType="Reservation">
        SELECT reservation_id, room_id, user_id, start_time, end_time, topic
        FROM reservations
        WHERE start_time &lt;= #{endTime} AND end_time &gt;= #{startTime}
    </select>

    <select id="selectReservationByRoomID" resultType="Reservation" parameterType="int">
        SELECT reservation_id as reservationId, room_id as roomId, user_id as userId, start_time as startTime, end_time as endTime, topic
        FROM reservations
        WHERE room_id = #{roomId}
    </select>

</mapper>

<select id="selectByRoomId" resultType="Room" parameterType="int">
    SELECT * FROM rooms WHERE room_id = #{roomId}
</select>

<select id="selectByUserId" resultType="User" parameterType="int">
    SELECT * FROM users WHERE user_id = #{userId}
</select>