如何使用 restTemplate Spring-mvc 发送多部分表单数据

读取 中的整个文件可能是大文件的内存消耗问题。ByteArrayResource

您可以使用以下命令在弹簧 mvc 控制器中代理文件上传：InputStreamResource

@RequestMapping(value = "/upload", method = RequestMethod.POST)
public ResponseEntity<?> uploadImages(@RequestPart("images") final MultipartFile[] files) throws IOException {
    LinkedMultiValueMap<String, Object> map = new LinkedMultiValueMap<>();
    String response;
    HttpStatus httpStatus = HttpStatus.CREATED;

    try {
        for (MultipartFile file : files) {
            if (!file.isEmpty()) {
                map.add("images", new MultipartInputStreamFileResource(file.getInputStream(), file.getOriginalFilename()));
            }
        }

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

        String url = "http://example.com/upload";

        HttpEntity<LinkedMultiValueMap<String, Object>> requestEntity = new HttpEntity<>(map, headers);
        response = restTemplate.postForObject(url, requestEntity, String.class);

    } catch (HttpStatusCodeException e) {
        httpStatus = HttpStatus.valueOf(e.getStatusCode().value());
        response = e.getResponseBodyAsString();
    } catch (Exception e) {
        httpStatus = HttpStatus.INTERNAL_SERVER_ERROR;
        response = e.getMessage();
    }

    return new ResponseEntity<>(response, httpStatus);
}

class MultipartInputStreamFileResource extends InputStreamResource {

    private final String filename;

    MultipartInputStreamFileResource(InputStream inputStream, String filename) {
        super(inputStream);
        this.filename = filename;
    }

    @Override
    public String getFilename() {
        return this.filename;
    }

    @Override
    public long contentLength() throws IOException {
        return -1; // we do not want to generally read the whole stream into memory ...
    }
}

您会收到异常，因为 RestTemplate 的默认 MessageConverters 都不知道如何序列化 MultipartFile 文件中包含的 InputStream。通过 RestTemplate 发送对象时，在大多数情况下，您希望发送 POJO。您可以通过将多部分文件的字节添加到多值映射而不是多部分文件本身来解决此问题。

我认为你的servlet部分也有问题。例如

File file1 = (File) req.getAttribute("userfile1");

应始终返回 null，因为 ServletRequest 的 getAttribute 方法不返回 request/form 参数，而是返回由 servlet 上下文设置的属性。你确定它实际上正在与你的卷曲示例一起使用吗？

下面是一个 Spring MVC 方法将文件转发到 servlet 的示例：

Servlet（尽管我测试了它在Spring MVC容器中运行），从这里改编：

@RequestMapping("/pi")
private void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {

  final String path = request.getParameter("destination");
  final Part filePart = request.getPart("file");
  final String fileName = request.getParameter("filename");

  OutputStream out = null;
  InputStream fileContent = null;
  final PrintWriter writer = response.getWriter();

  try {
    out = new FileOutputStream(new File(path + File.separator
            + fileName));
    fileContent = filePart.getInputStream();

    int read = 0;
    final byte[] bytes = new byte[1024];

    while ((read = fileContent.read(bytes)) != -1) {
      out.write(bytes, 0, read);
    }
    writer.println("New file " + fileName + " created at " + path);

  } catch (FileNotFoundException fne) {
    writer.println("You either did not specify a file to upload or are "
            + "trying to upload a file to a protected or nonexistent "
            + "location.");
    writer.println("<br/> ERROR: " + fne.getMessage());

  } finally {
    if (out != null) {
      out.close();
    }
    if (fileContent != null) {
      fileContent.close();
    }
    if (writer != null) {
      writer.close();
    }
  }
}

弹簧MVC方法：

@ResponseBody
@RequestMapping(value="/upload/", method=RequestMethod.POST, 
        produces = "text/plain")
public String uploadFile(MultipartHttpServletRequest request) 
        throws IOException {

  Iterator<String> itr = request.getFileNames();

  MultipartFile file = request.getFile(itr.next());
  MultiValueMap<String, Object> parts = 
          new LinkedMultiValueMap<String, Object>();
  parts.add("file", new ByteArrayResource(file.getBytes()));
  parts.add("filename", file.getOriginalFilename());

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

  HttpEntity<MultiValueMap<String, Object>> requestEntity =
          new HttpEntity<MultiValueMap<String, Object>>(parts, headers);

  // file upload path on destination server
  parts.add("destination", "./");

  ResponseEntity<String> response =
          restTemplate.exchange("http://localhost:8080/pi", 
                  HttpMethod.POST, requestEntity, String.class);

  if (response != null && !response.getBody().trim().equals("")) {
    return response.getBody();
  }

  return "error";
}

使用这些，我可以通过以下curl成功地通过MVC方法将文件上传到servlet：

curl --form file=@test.dat localhost:8080/upload/