mybatis <foreach>标签

在查看好友动态的需求里用到过

<select id="selectConcernDynamicByPage" parameterType="DynamicListOption"        resultMap="BaseResultMap">    select    <include refid="Base_Column_List"/>    <if test="userIds !=null">        AND  user_id in        <foreach collection="userIds" index="index" item="item" open="(" separator="," close=")">            #{item}        </foreach>    </if></select>

DynamicListoption里写了

private List<Long> userIds;