Downloading a file from spring controllers

Question

I have a requirement where I need to download a PDF from the website. The PDF needs to be generated within the code, which I thought would be a combination of freemarker and a PDF generation framework like iText. Any better way?

However, my main problem is how do I allow the user to download a file through a Spring Controller?

Answer 1

@RequestMapping(value = "/files/{file_name}", method = RequestMethod.GET)
public void getFile(
    @PathVariable("file_name") String fileName, 
    HttpServletResponse response) {
    try {
      // get your file as InputStream
      InputStream is = ...;
      // copy it to response's OutputStream
      org.apache.commons.io.IOUtils.copy(is, response.getOutputStream());
      response.flushBuffer();
    } catch (IOException ex) {
      log.info("Error writing file to output stream. Filename was '{}'", fileName, ex);
      throw new RuntimeException("IOError writing file to output stream");
    }

}

Generally speaking, when you have response.getOutputStream(), you can write anything there. You can pass this output stream as a place to put generated PDF to your generator. Also, if you know what file type you are sending, you can set

response.setContentType("application/pdf");