docs: @Override
      public String recv(InputStream ins) throws IOException {
          FileOutputStream out = null;
          InputStream in = null;
          try {
              out = new FileOutputStream(fileName);
              in = new BufferedInputStream(ins);
              // 通过ioutil 对接输入输出流，实现文件下载
              IOUtils.copy(in, out);
              out.flush();
          } catch (IOException e) {
              e.printStackTrace();
          } finally {
              // 关闭流
              IOUtils.closeQuietly(in);
              IOUtils.closeQuietly(out);
          }
          return fileName;
      }