Transfer .xls files through POST request in Java REST Api

Question

I'm new to Spring and I have some troubles in receiving a .xls file from the front-end through a POST request. Bassicaly when I accesss the link "Project/File" I receive error code 400(bad request) but the parameters names are the same both in front-end and back-end.

Here is my code so far:

@Controller
public class RestController {

    @Autowired
    private FileService fileService;

    @Consumes("application/vnd.ms-excel")
    @RequestMapping(value = "Project/File",
            method = {RequestMethod.POST, RequestMethod.GET},
            params = {"inputXLS"})
    public @ResponseBody void getCitiriContoriMecanici(
            @RequestParam(value = "inputXLS" , required = true) InputStream inputStream) throws IOException{

        //transform the InputStream to an array of bytes;
        byte[] bytes = IOUtils.toByteArray(inputStream);

        //create a new .xls file
        File file = new File("TEST.xls");  
        FileOutputStream fileOutputStream = new FileOutputStream(file);
        //write a the bytes to a new .xls file
        fileOutputStream.write(bytes);
        fileOutputStream.flush();
        fileOutputStream.close();

        fileService.getFileFromFrontEnd();//this method is used to parse the .xls file
    }

}

Can anyone give me an idea how to solve this problem?

Answer 1

It looks like you're trying to implement a file upload control with a Jax-RS @Consumes annotation. The first problem I see is that you're trying to directly consume application/vnd.ms-excel, but that's not what your file upload will present coming from your front end. It expects multipart/form-data as the mime type. Doing that, you can then have a @RequestParam("file") MultipartFile file parameter on your request mapping to get a hold of the file.

I've never used Jax-RS annotations in my application, but you wouldn't even need it. Your request mapping can be as simple as this:

@RequestMapping(value ="Project/File", method = RequestMethod.POST)
public void handleFileUpload(@RequestParam("file") MultipartFile file)

Spring has a nice guide showing what you need to do for file upload if you want to see further details https://spring.io/guides/gs/uploading-files/

I should also note, you've annotated the return type of your mapping with @RequestBody, but your return type is void, so there's no need for @RequestBody in this case. I'd suggest at least having a return type of HttpStatus and then returning HttpStatus.OK if the upload succeeded.