用于将文件上载到任何服务或终结点
私有字符串testExchange（文件文件）{

//add file
LinkedMultiValueMap<String, Object> params = new LinkedMultiValueMap<>();
params.add("file", new FileSystemResource(file));

HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.MULTIPART_FORM_DATA);

HttpEntity<LinkedMultiValueMap<String, Object>> requestEntity =
        new HttpEntity<>(params, headers);

ResponseEntity<String> responseEntity = restTemplate.exchange(
        "/upload-file",
        HttpMethod.POST,
        requestEntity,
        String.class);

HttpStatus statusCode = responseEntity.getStatusCode();
if (statusCode == HttpStatus.ACCEPTED) {
    result = responseEntity.getBody();
}
return result;

}