File Download In Spring

In order to implement a file download in Spring, the key is returning null instead of a ModelAndView object. This controller that I created below is specifically for text/ascii data. You'd need to change the content type appropriately in order to download other file types.

public class DownloadController implements Controller {
 /*
  * Spring dependency injection
  */
 private XService xService;

 public void setxService(
   XService xService) {
  this.xService = xService;
 }

 public ModelAndView handleRequest(HttpServletRequest request,
   HttpServletResponse response) throws Exception {
  String idStr = request.getParameter("id");
  if (idStr != null) {
   long id = Long.parseLong(idStr);
   String data = xService.getData(id);
   doDownload(request, response, data, "file" + idStr + ".xml");
  }
  return null;
 }

 private void doDownload(HttpServletRequest request,
   HttpServletResponse response, String data, String filename)
   throws IOException {
  int length = data.length();
  ServletOutputStream op = response.getOutputStream();
 
  response.setContentType("text/plain");
  response.setContentLength(data.length());
  response.setHeader("Content-Disposition",
    "attachment; filename=\"" + filename + "\"");

  byte[] bbuf = data.getBytes();
  op.write(bbuf, 0, length);
  op.flush();
  op.close();
 }
}