MultipartFile获取Base64编码

File file = new File(mFile.getOriginalFilename());
FileUtils.copyInputStreamToFile(mFile.getInputStream(), file);
try (FileInputStream fis = new FileInputStream(file)) {
  byte[] buf = new byte[(int) file.length()];
  fis.read(buf);
  return new String(Base64.encodeBase64(buf), StandardCharsets.ISO_8859_1);
} catch (IOException e) {
  log.error(e.getMessage(), e);
} finally {
  if (file.exists()) {
    file.delete();
  }
}