mybatis中使用in查询时的注意事项

一、 当查询的参数只有一个时

findByIds(List ids)

a. 如果参数的类型是List, 则在使用时，collection属性要必须指定为 list

<select id="getPostOrderListByParam"
resultType="com.qlyd.common.po.post.PostInfo"
parameterType="com.qlyd.common.inparam.manage.postmanage.PostManageQueryParam">
select inner_id,circle_id, user_id, user_type,
word_content, img_content, status, publish_time, comment_sum,
view_sum, order_num, perfect_num from circle_posts_info
WHERE
<if test="circle_id !=null">
circle_id=#{circle_id} and order_num !=1000
<if test="postids !=null">
or inner_id in
<foreach item="item" index="index" collection="postids"
open="(" separator="," close=")">
#{item}
</foreach>
</if>
order by order_num,publish_time DESC
</if>
<if test="circle_id ==null">
perfect_num !=1000
<if test="postids !=null">
or inner_id in
<foreach item="item" index="index" collection="postids"
open="(" separator="," close=")">
#{item}
</foreach>
</if>
order by perfect_num,publish_time DESC
</if>
</select>

findByIds(Long[] ids)

b. 如果参数的类型是Array,则在使用时，collection属性要必须指定为 array

<select id="findByIdsMap" resultMap="BaseResultMap">
select
<include refid="Base_Column_List" />
from jria where ID in
<foreach item="item" index="index" collection="array"
open="(" separator="," close=")">
#{item}
</foreach>
</select>

二、当查询的参数有多个时,例如 findByIds(String name, Long[] ids)

这种情况需要特别注意，在传参数时，一定要改用Map方式, 这样在collection属性可以指定名称

下面是一个示例

Map<String, Object> params = new HashMap<String, Object>(2);
params.put("name", name);
params.put("ids", ids);
mapper.findByIdsMap(params);

<select id="findByIdsMap" resultMap="BaseResultMap">
select
<include refid="Base_Column_List" />
from jria where ID in
<foreach item="item" index="index" collection="ids"
open="(" separator="," close=")">
#{item}
</foreach>
</select>