Error handling by redirection in spring download file controller

Question

This question nicely explains on how to write download file controllers in spring. This question nicely explains that Post request cannot be sent using response.sendRedirect()

I would like the user to be redirected to the same page with an error about what caused file download error. Here is the workflow

1. User hits www.abc.com/index [controller has mapping /index.jsp and return ModelAndView]
2. At this page, we have a file download which has URL www.abc.com/download?resource_id=123. [controller has mapping /download and returns void]
3. When there is error in file download, user should be redirected to www.abc.com/index with some error display.
4. When there is no error in file download, user stays at the same page and file download dialog appears.

Following is a snippet for forwarding:

@RequestMapping(/download)
public void execute(@RequestParam(value = "resource_id" required = true) final String resource, final HttpServletRequest request, final HttpServletResponse response) {
    try {
        //some processing
    } catch {
        RequestDispatcher dispatcher = request.getRequestDispatcher("/index" + "?is_downloaded=false");
        dispatcher.forward(request, response)
    }
}

@RequestMapping(/index)
public void execute(@RequestParam(value = "is_downloaded" required = false) final String isDownloaded, final HttpServletRequest request) {
    //do stuff here
}

Step 3 is the problem.

• Using forwarding changes the URL to the download URL of the report on error.
• Using redirect as response.sendRedirect() with hidden parameters is impossible would not modify the URL at all.
• Using redirect as response.sendRedirect() with hidden parameters and would introduce "?is_downloaded=false" at the end of URL

Can anyone tell a workaround for this.

Answer 1

I've been having a similar issue and solved it with the below code.

I have the following exception handler in my controller. If there is an error this takes care of the re-direct and error messaging.

@ExceptionHandler(FileNotFoundException.class)
public ModelAndView exceptionHandler(Exception ex) {
    ModelAndView modelAndView = new ModelAndView();
    modelAndView.setViewName("rescues/general");
    modelAndView.addObject("message", ex.getMessage());
    return modelAndView;
}

Here is the RequestMapping

@RequestMapping(value = "s3Download.request", method = RequestMethod.GET)
@ResponseBody
public ResponseEntity<InputStreamResource> download(@RequestParam(value = "s3key") String s3Key)
        throws IOException {
    HttpHeaders responseHeaders = new HttpHeaders();
    InputStreamResource inputStreamResource = s3DownloadService.getS3File(s3Key, responseHeaders);
    return new ResponseEntity<>(inputStreamResource, responseHeaders, HttpStatus.OK);
}

If the files are locally on your server you can use a FileSystemResource in place of the InputStreamResource.

The service layer takes care of setting the response header values on the HttpHeaders object

responseHeaders.setContentType(MediaType.parseMediaType(objectMetaData.getContentType()));
responseHeaders.setContentLength(objectMetaData.getContentLength());
responseHeaders.setContentDispositionFormData("attachment", fileName);