Sending a file as a http response

Question

I am accessing a file on the file system and sending it back to the HttpResponse with the below code. My only problem is that every now and then the file transfer gets cut and the file is now downloaded completely. This does not happen after a certain size and a transfer that didn't work the first time might work the second.
The problem also occurs more often from remote sites than from my machine which resides on the same local network as the machine.
Is there anything in the code or the surrounding environment which I need to be aware of in order to fix this problem?
  public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
    String filename = request.getParameter("fileName");
    FileDataSource fds = new FileDataSource(filename);
    DataHandler dh = new DataHandler(fds);
    response.setContentType(fds.getContentType());
    response.setHeader(
      "Content-Disposition",
      "attachment; filename=" + filename);
    dh.writeTo(response.getOutputStream());
  }

Answer 1

I've recently written a "file download servlet", too and found it to work quite well. There are some issues when using IExplore for Mac I'm aware of but usually transfers complete successfully.
It could be that the network reliability in your region is pretty poor and a lot of packets get dropped on the way - that would also cause a transfer to fail.
FileDataSource fds = new new FileDataSource(filename);
DataHandler dh = new DataHandler(fds);What are these two classes FileDataSource and DataHandler? Maybe they are causing the problems.
If you just want to download files and display a "Save file as..." dialog to the user, you don't have to use any third party classes/libs. Just do
File file = ...
String filename = ...
response.setContentType("application/octect-stream");
response.setHeader(
     "Content-Disposition",
     "attachment; filename=" + filename);
// Setting the content length ist not mandatory but provides the
// client with enough information to display a progress bar
response.setContentLength((int)file.length());
// The rest is just plain "read it in, write it out" stuff
BufferedInputStream in = new BufferedInputStream(
     new FileInputStream(file));
BufferedOutputStream out = new BufferedOutputStream(
     response.getOutputStream());
int len;
byte[] buf = new byte[1024]; // or whatever buffer size you like best
while((len = in.read(buf)) != -1)
     out.write(buf, 0, len);
in.close();
out.flush();
out.close();Hope I could help,
phil