Problem when writing big files to ServletOutputStream

I am using the following code to write files to servlet output stream. The problem is the browser is not downloading the entire file when the file size grows above 10 MB. Any help would be greatly helpful.

FileInputStream fis = new FileInputStream(new File(fileName));
response.setHeader("Content-Disposition:", "attachment;filename=" + fileName );
BufferedInputStream bis= new BufferedInputStream(fis);
ServletOutputStream sos = response.getOutputStream();
byte[] buffer = new byte[5000];
response.setHeader("Content-Length:", String.valueOf (bis.available()));
while (true) {
   int bytesRead = bis.read(buffer, 0, buffer.length);
   if (bytesRead < 0)
   break;
   sos.write(buffer, 0, bytesRead);
}
fis.close();
sos.flush();
sos.close();

Problem when writing big files to ServletOutputStream

response.setHeader("Content-Length:", String.valueOf (bis.available()));