private String extractFileNameFromContentString(String content) throws WxErrorException {
    if (content == null || content.length() == 0) {
      throw new WxErrorException("无法获取到文件名，content为空");
    }

    Matcher m = PATTERN.matcher(content);
    if (m.matches()) {
      return m.group(1);
    }

    throw new WxErrorException("无法获取到文件名，header信息有问题");
  }