异常原因: 问题不是mybatis不支持“<”,而是xml不支持这个符号
解决案例: SELECT * FROM tb_km_activity a WHERE a.is_del = #{isDel} AND a.activity_end_time >= #{now} <![CDATA[and a.activity_start_time <= #{now} ]]> AND b.user_status = 1 ORDER BY a.id DESC