Performance issues in file download servlet

Question

        FileInputStream in = null;
        ServletOutputStream sos = res.getOutputStream();
          File f = new File(path);
          if(f.exists())  {
            in = new FileInputStream(f);
            int length = (int)f.length();
            byte[] input = new byte[length];
            res.setContentType ("application/octet-stream");
            res.setHeader("Content-Disposition", "attachment; filename=\""+fileName+"\"");
            res.setContentLength(length);
            if(length != 0) {
              while ((in != null) && ((length = in.read(input)) != -1))  {   // read
                sos.write(input,0, input.length);   // write
          }Hi experts, the above is a block of code that sends a file to a client machine through servlet. One problem I am having now is that it frequently cause the server to run out of memory. Is it because of the way I read the FileInputStream is not efficient?
            byte[] input = new byte[length];
            if(length != 0) {
              while ((in != null) && ((length = in.read(input)) != -1))  {   // read
                sos.write(input,0, input.length);   // write
              }It seems that my code reads an entire file into memory before it writes anything to the client, so when there are many people downloading files, the server will run out of memory. Is it true?
I am not very familiar with the read() and write() methods in the inputstream and output stream classes. So I hope someone here can tell me whether the above code is indeed the cause of the problem. If not, then I can troubleshoot my other servlets and JSPs.
Thanks!

Answer 1

try not to create a byte[] with the file size
try to make it a fix one
e.g.new byte[1024]
treat it as a package to sendThanks. But is 1024 too small a size for sending files throught the internet? What is the best size to used?