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>