下载文件

public ActionForward fileDownload(ActionMapping mapping, ActionForm form,
   HttpServletRequest request, HttpServletResponse response){
  String inUrl = request.getParameter("url");
  
  String uploadRootUrl = getUploadRootUrl();
  
  String url = uploadRootUrl + inUrl;
  
  String flName = inUrl.substring(inUrl.indexOf(".")+1);
  
  BufferedInputStream fin = null;
  ServletOutputStream fout = null;
  try {
   File f = new File(url);
   fin = new BufferedInputStream(new FileInputStream(f));
   fout = response.getOutputStream();
   
   response.setContentType("application/" + flName);
   response.setHeader("content-disposition", "attachment; filename=down." + flName);
   response.setContentLength((int) f.length());

   log.error("user download from Datums,the file name is [" +
   inUrl.substring(inUrl.lastIndexOf(File.separator) + 1) + "]");

   int length = (int) f.length();

   if (length != 0) {
    byte[] b = new byte[2048];
    while (fin != null && (length = fin.read(b)) != -1) {
     fout.write(b, 0, length);
    }
   }
   
  } catch (FileNotFoundException e) {
       log.info("no found file");
   return mapping.findForward("noFile");
  } catch (IOException e) {
   e.printStackTrace();
  } finally {
   try {
    if (fin != null) {
     fin.close();
    }
    if (fout != null) {
     fout.close();
    }
   } catch (IOException e) {
    e.printStackTrace();
   } catch (Exception e) {
    e.printStackTrace();
   }
  }
  
  return null;
 }