Returning JSON response for Spring MVC Post request

Question

I have the below controller method which is uploading files to my server. I would like to return JSON for Plupload's status. However the response seems to be sent back as a dispatch rather than a json @ResponseBody. Any Ideas?

    private static final String RESP_SUCCESS = "{\"jsonrpc\" : \"2.0\", \"result\" : \"success\", \"id\" : \"id\"}";
    private static final String RESP_ERROR = "{\"jsonrpc\" : \"2.0\", \"error\" : {\"code\": 101, \"message\": \"Failed to upload file.\"}, \"id\" : \"id\"}";

    @RequestMapping(method = RequestMethod.POST)
    public String uploadItem(@RequestBody MultipartFile file,
                             @RequestParam String name,
                             @RequestParam(required = false, defaultValue = "-1") int chunks,
                             @RequestParam(required = false, defaultValue = "-1") int chunk) {
        Media media = new Media();
        try {
            Path path = Paths.get("/Users/username/Desktop/Test", file.getOriginalFilename());
            media.setContentType(file.getContentType());
            media.setFileName(file.getOriginalFilename());
            media.setFileSize(file.getSize());
            media.setFilePath(path.toString());
            if (media.getContentType().contains("image")) {
                Image image = new Image();
                image.setImagePath(path.toString());
                imageDao.save(image);
            }
            byte[] bytes = file.getBytes();
            Files.write(path, bytes, StandardOpenOption.CREATE);
            mediaDao.save(media);
            return RESP_SUCCESS;
        } catch (IOException e) {
            e.printStackTrace();

        }
        return RESP_ERROR;
    }
}

Throws the following error:

WARN - No mapping found for HTTP request with URI [/{"jsonrpc" : "2.0", "result" : "success", "id" : "id"}] in DispatcherServlet with name 'cr'

Answer 1

I think your method should be annotated with @ResponseBody.

@RequestMapping(method = RequestMethod.POST)
@ResponseBody
public  String uploadItem(@RequestBody MultipartFile file,
                             @RequestParam String name,
                             @RequestParam(required = false, defaultValue = "-1") int chunks,
                             @RequestParam(required = false, defaultValue = "-1")

This is how Spring checks for Json conversion:

• Jackson library is existed in the project classpath
• The mvc:annotation-driven is enabled
• Return method annotated with @ResponseBody

Spring will handle the JSON conversion automatically.