用RestTemplate发送MultipartFile为参数的请求

```
@Autowired
RestTemplate restTemplate;
@PostMapping("/send")
public TopicFileResponse send(String url,String path) {

    HttpHeaders headers = new HttpHeaders();
    MediaType type = MediaType.parseMediaType("multipart/form-data");
    // 设置请求的格式类型
    headers.setContentType(type);
    FileSystemResource fileSystemResource = new FileSystemResource(path);
    MultiValueMap form = new LinkedMultiValueMap<>();
    form.add("name", fileSystemResource);
    HttpEntity> files = new HttpEntity<>(form, headers);
    ResponseEntity responseResponseEntity = restTemplate.postForEntity(url, files, TopicFileResponse.class);
    TopicFileResponse body = responseResponseEntity.getBody();
    return body;
}
```
> 其中TopicFileResponse是对方请求该返回的结果