JAVA保存类似微信样式的群组头像（群组拉人，踢人的时候用）

/**
 * 保存群组头像
 *
 * @param groupId 群组ID
 */

//Hibernate 操作数据库，List<ImUsr> getAvatar(@Param("groupId") String groupId);数据库SQ：

<!-- 获取群组9个成员的头像 -->
<select id="getAvatar" resultMap="com.weelang.zxsw.im.mapper.ImUserMapper.imUsrResultMap">
    SELECT u.id, u.avatar
    FROM im_user u, im_group_member gm
    WHERE u.id = gm.member_id
        AND gm.group_id = #{groupId}
        AND gm.deletion = '0'
        AND u.deletion = '0'
        AND u.avatar is not null
    ORDER BY gm.created
    LIMIT 9
</select>

//传入群组ID
public void saveAvatar(String groupId) {
//json对象
  List<ImUsr> usrs = imGroupMapper.getAvatar(groupId);
//类型不匹配，需要转换字符串类型
  List<String> uids = Lists.newArrayList();
  List<String> paths = Lists.newArrayList();

    for (ImUsr usr : usrs) {
        uids.add(usr.getId());
        paths.add(usr.getAvatar());
    }
    try {
        ImGroup imGroup = this.findOne(groupId);
        //把uids转化，用逗号分隔的字符串
        String aids = Strings.join(uids, ",");
        if (imGroup != null && Strings.isNotBlank(aids) && !aids.equals(imGroup.getAvatarIds())) {
            //存放路径
            String avatar = avatarPath + Identities.uuid2() + ".jpg";
            String filename = uploadPath + avatar;
            //调用工具类函数（1，用户头像路径列表【类型】List<String>，2，生成后的头像保存路径【类型】String）
           Images.avatar(paths, filename);
　　　　　　imGroup.setAvatar(avatar);
　　　　　　imGroup.setAvatarIds(aids);
　　　　　　this.save(imGroup);

        }
    } catch (IOException e) {
        logger.error("生成群组头像失败：{" + groupId + "}：" + e.getMessage());
    }
}