mybatis insert前获取要插入的值

    <insert id="insertRequestItem" parameterType="requestItemModel">

        <selectKey keyProperty="itemId" resultType="String" order="BEFORE">
            select max(0 + item_id) + 1 from DUING.M_REQUEST_ITEM where kind_id = #{kindId}
        </selectKey>

        INSERT INTO M_REQUEST_ITEM (
            item_id,
            create_datetime,
            update_datetime
            )
        VALUES (
            #{itemId},
            now(),
            now()
            )
    </insert>