使用客户端 Java 代码进行 Spring boot 分段文件上传

我在 Spring Boot 中编写了一个安静的 Web 服务来接收该文件。

@RequestMapping(value = "/upload", method = RequestMethod.POST)
@ResponseBody
public void uploadFile(@RequestParam("file") MultipartFile uploadfile) {
    System.out.println("filename: " + uploadfile.getName());
}

我们怎样才能将文件从客户端 java 代码上传到 Web 服务。而不是 AJAX 调用或 HTML 页面表单多部分请求？

下面的代码使用 JSON 对象调用 Web 服务。像这样我想接收上面写的网络服务中的文件。

void clientRequest(String server_url, JSONObject fileObj){

  try {

    URL url = new URL(server_url);
    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    conn.setDoOutput(true);
    conn.setRequestMethod("POST");
    conn.setRequestProperty("Content-Type", "application/json");

    OutputStream os = conn.getOutputStream();
    os.write(fileObj.toString().getBytes());
    os.flush();

    BufferedReader br = new BufferedReader(new InputStreamReader(
            (conn.getInputStream())));

    String output;
    System.out.println("Output from Server .... \n");
    while ((output = br.readLine()) != null) {
        logger.info("output :: " + output);
    }

    conn.disconnect();

  } catch (Exception e) {
    e.printStackTrace();
  }
}

你可以使用 Spring 的HttpEntity随着ByteArrayResource要上传文件，这里是一个示例：

MultiValueMap<String, Object> data = new LinkedMultiValueMap<String, Object>();
ByteArrayResource resource = new ByteArrayResource(file.getBytes()) {
    @Override
    public String getFilename() {
        return file.getName();
    }
};
data.add("file", resource);

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

HttpEntity<MultiValueMap<String, Object>> requestEntity = new HttpEntity<MultiValueMap<String, Object>>(data, requestHeaders);

final ResponseEntity<<SomeClass>> responseEntity = restTemplate.exchange(<url>, 
        HttpMethod.POST, requestEntity, new ParameterizedTypeReference<SomeClass>(){});

SomeClass result = responseEntity.getBody();