Spring RestTemplate：同时发布图像和对象

Question

我的用户可以在我的服务器上发布一张食物的照片和一个关于食物的帖子。

例如，假设某人看到了好吃的东西，拍了一张照片，然后写上“Tasty！”在照片下面。照片被发送到服务器，消息“Tasty！”包括用户名、日期、位置等,通过一个api调用在一个名为“POST”的对象中发送到我的服务器。

我在我的android端写了以下代码：

    final String url = Constants.POST_PICS;
    RestTemplate restTemplate = RestClientConfig.getRestTemplate(context, true);
    //adding StringHttpMessageConverter, formHttpMessageConverter and MappingJackson2HttpMessageConverter to restTemplate
    restTemplate.getMessageConverters().add(new StringHttpMessageConverter());
    FormHttpMessageConverter formHttpMessageConverter = new FormHttpMessageConverter();
    restTemplate.getMessageConverters().add(formHttpMessageConverter);
    restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter());
    //putting both objects into a map
    MultiValueMap<String, Object> map = new LinkedMultiValueMap<String, Object>();
    map.add("image", new FileSystemResource(file));
    map.add("post", post);
    HttpHeaders imageHeaders = new HttpHeaders();
    //setting content type to multipart as the image is a multipart file
    imageHeaders.setContentType(MediaType.MULTIPART_FORM_DATA);
    HttpEntity<MultiValueMap<String, Object>> imageEntity = new HttpEntity<MultiValueMap<String, Object>>(map, imageHeaders);
    ResponseEntity<Post> response = restTemplate.exchange(url, HttpMethod.POST, imageEntity, Post.class);
    return response.getBody();

        @RequestMapping(value = "/uploadpostpic", method = RequestMethod.POST)
public Post uploadPostWithPic(@RequestParam("image") MultipartFile srcFile,
                                  @RequestParam("post") Post post) {
    return serviceGateway.uploadPostWithPic(srcFile, post);
}

请求网络执行过程中发生异常：无法写入请求：找不到请求类型[model.post]的合适的HttpMessageConverter

org.springframework.http.converter.httpmessageNotWritableException：无法写入请求：找不到适合请求类型[model.post]的HttpMessageConverter

我怀疑这与内容类型设置为MULTIPART_FORM_DATA有关，但我需要设置为这个，因为我需要将图片传送到服务器。

编辑：

我看过这些帖子：

Resttemplate表单/Multipart:image+POST中的

    final String url = Constants.POST_PIC;
    RestTemplate restTemplate = new RestTemplate();
    restTemplate.getMessageConverters().add(new StringHttpMessageConverter());
    restTemplate.getMessageConverters().add(new ByteArrayHttpMessageConverter());
    restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter());
    restTemplate.getMessageConverters().add(new ResourceHttpMessageConverter());

    FormHttpMessageConverter formHttpMessageConverter = new FormHttpMessageConverter();
    formHttpMessageConverter.addPartConverter(new MappingJackson2HttpMessageConverter());
    formHttpMessageConverter.addPartConverter(new ResourceHttpMessageConverter()); // This is hope driven programming
    formHttpMessageConverter.addPartConverter(new ByteArrayHttpMessageConverter());

    restTemplate.getMessageConverters().add(formHttpMessageConverter);

    MultiValueMap<String, Object> multipartRequest = new LinkedMultiValueMap<>();

    byte[] bFile = new byte[(int) imageFile.length()];
    FileInputStream fileInputStream;

    //convert file into array of bytes
    fileInputStream = new FileInputStream(imageFile);
    fileInputStream.read(bFile);
    fileInputStream.close();

    ByteArrayResource bytes = new ByteArrayResource(bFile) {
        @Override
        public String getFilename() {
            return "file.jpg";
        }
    };

    //post portion of the multipartRequest
    HttpHeaders xHeader = new HttpHeaders();
    xHeader.setContentType(MediaType.APPLICATION_JSON);
    HttpEntity<Post> xPart = new HttpEntity<>(post, xHeader);
    multipartRequest.add("post", xPart);

    //picture portion of the multipartRequest
    HttpHeaders pictureHeader = new HttpHeaders();
    pictureHeader.setContentType(MediaType.IMAGE_JPEG);
    HttpEntity<ByteArrayResource> picturePart = new HttpEntity<>(bytes, pictureHeader);
    multipartRequest.add("srcFile", picturePart);

    //adding both the post and picture portion to one httpentity for transmitting to server
    HttpHeaders header = new HttpHeaders();
    header.setContentType(MediaType.MULTIPART_FORM_DATA); 
    HttpEntity<MultiValueMap<String, Object>> requestEntity = new HttpEntity(multipartRequest, header);
    return restTemplate.postForObject(url, requestEntity, Post.class);

public Post uploadPostPic(MultipartFile srcFile, Post post) {
    Post savedPost = repo.save(post);
 }

我正在将其保存到我的存储库中，但错误是：

java.lang.IllegalArgumentException: Entity must not be null!

Answer 1

尝试这样做：在这里发送jsonString，稍后使用ObjectWriter将其转换为object。

@RequestMapping(value = "/uploadMultipleFile", method = RequestMethod.POST)
    public @ResponseBody
    String uploadMultipleFileHandler(@RequestParam("name") String[] names,
            @RequestParam("file") MultipartFile[] files) {

        if (files.length != names.length)
            return "Mandatory information missing";

        String message = "";
        for (int i = 0; i < files.length; i++) {
            MultipartFile file = files[i];
            String name = names[i];
            try {
                byte[] bytes = file.getBytes();

                // Creating the directory to store file
                String rootPath = System.getProperty("catalina.home");
                File dir = new File(rootPath + File.separator + "tmpFiles");
                if (!dir.exists())
                    dir.mkdirs();

                // Create the file on server
                File serverFile = new File(dir.getAbsolutePath()
                        + File.separator + name);
                BufferedOutputStream stream = new BufferedOutputStream(
                        new FileOutputStream(serverFile));
                stream.write(bytes);
                stream.close();

                logger.info("Server File Location="
                        + serverFile.getAbsolutePath());

                message = message + "You successfully uploaded file=" + name
                        + "<br />";
            } catch (Exception e) {
                return "You failed to upload " + name + " => " + e.getMessage();
            }
        }
        return message;
    }
}

编辑：

最终，我不得不使用jsonString来解决我的问题。这并不理想,因为url最终会变得很长,但这是解决我问题的最快方法：

ObjectMapper mapper = new ObjectMapper();
Staff obj = new Staff();

//Object to JSON in String
String jsonInString = mapper.writeValueAsString(obj);

//JSON from String to Object
Staff obj = mapper.readValue(jsonInString, Staff.class);