Re: StringIndexOutOfBoundsException in File Downloads

On Tuesday 08 June 2004 15:53, Srikanth Addala wrote:
> I think we are using cms version 5.1.2. I have attached the file to
> this mail. I think you have sent this file to one of my colleague
> (Steve) in Sept'03 to handle the file names properly.

I assume by "you" you mean the collective "you" as in "you Red Hat".
If you really do mean me personally, I can't recall what I was smoking
at the time.

The code in question falls short of perfection on a number of counts.
To my taste, some of the things that are wrong with it include the
following:

 * The instance fields m_queryPart, m_fileNamePart, endingPart are
   only used by the offending method stripFileName.  As such, these
   variables should be local to the method rather than being fields.
 * Rather than traversing the URL backwards looking for '/' and '?',
   it would be much clearer if you used String#lastIndexOf(char) to
   find and extract the substring you are looking for.
 * The use of StringBuffer#insert(0, ch) is terrible performance-wise.


> Can you please let me know if you see any thing that could be wrong.

I suggest you test this method in isolation like so:

$ cd /tmp
$ cat Main.java 
public class Main {
    private StringBuffer m_queryPart = new StringBuffer();
    private StringBuffer m_fileNamePart = new StringBuffer();
    private String endingPart;

    public static void main(String[] args) {
        new Main().run();
    }

    private void run() {
        log("http://example.com/foo/bar/baz?foo=quuz&a=1");
        log("http://example.com/foo/bar/?foo=quuz&a=1");
        log("http://example.com/foo/bar/?foo=quuz&f=/tmp/bar");
    }

    private void log(String url) {
        System.out.println(url);
        System.out.print("  ");
        System.out.println(stripFileName(url));
    }

    private String stripFileName(String url) {
        endingPart = null;
        m_queryPart.delete(0, m_queryPart.length());
        m_fileNamePart.delete(0, m_queryPart.length());
        for (int i = 1; i < url.length(); i++) {
            char ch = url.charAt(url.length() - i);
            // s_log.debug("ch: " + ch);
            if (ch == '/') {
                break;
            }
            m_queryPart.insert(0, ch);
            if (ch =='?') {
                for (int j = i; j < url.length(); j++) {
                    ch = url.charAt(url.length() - j);
                    if (ch == '/') {
                        break;
                    }
                    m_fileNamePart.insert(0, ch);
                }
            }
        }
        endingPart = m_fileNamePart.toString() + m_queryPart.toString();
        url = url.substring(0, url.length() - endingPart.length());
        return url;
    }
}

$ javac Main.java 

$ java -cp . Main
http://example.com/foo/bar/baz?foo=quuz&a=1
  http://example.com/foo/
http://example.com/foo/bar/?foo=quuz&a=1
  http://example.com/foo
http://example.com/foo/bar/?foo=quuz&f=/tmp/bar
  http://example.com/foo/bar/?foo=quuz&f=


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