android - Spring RestTemplate : post both an image and an object at the same time

Question

我的用户可以在我的服务器上张贴食物的照片和食物的内容。

例如，假设有人看到好吃的东西，拍下它的照片，然后写下“好吃!”在图片下方。照片被发送到服务器，消息“好吃!”包括用户名、日期、位置等在内的一个名为“Post”的对象使用一个 API 调用发送到我的服务器。

我在我的android端写了下面的代码:

    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();

这是Spring端的代码:

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

我收到一个错误:

An exception occurred during request network execution :Could not write request: no suitable HttpMessageConverter found for request type [Model.Post]

org.springframework.http.converter.HttpMessageNotWritableException: Could not write request: no suitable HttpMessageConverter found for request type [Model.Post]

我怀疑这与设置为 MULTIPART_FORM_DATA 的内容类型有关，但我需要将其设置为此，因为我需要将图片传输到服务器。

是否可以同时使用 restTemplate 向上游传输一个多部分文件和另一个对象？

编辑:

我看过这些帖子:

Resttemplate form/multipart: image + JSON in POST

Sending Multipart File as POST parameters with RestTemplate requests

并根据他们的指导尝试了这段代码:

    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);

另一方面，post = null，我不确定它为什么为 null。

这就是我想在服务器端做的所有事情:

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

我正在将它保存到我的存储库中，错误是:

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

Answer 1

尝试这样的事情: 在此处发送 jsonString，稍后使用 objectwriter 将其转换为对象。如果您需要更多解释，请告诉我。

@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;
    }
}

已编辑:

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，但这是解决我的问题的最快方法:

请查看 mykong 关于如何将对象转换为 jsonString 并将它们重新转换回对象的建议:

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);

http://www.mkyong.com/java/jackson-2-convert-java-object-to-from-json/