Java code/library for generating slugs (for use in pretty URLs)

Normalize your string using canonical decomposition:

  private static final Pattern NONLATIN = Pattern.compile("[^\\w-]");
  private static final Pattern WHITESPACE = Pattern.compile("[\\s]");

  public static String toSlug(String input) {
    String nowhitespace = WHITESPACE.matcher(input).replaceAll("-");
    String normalized = Normalizer.normalize(nowhitespace, Form.NFD);
    String slug = NONLATIN.matcher(normalized).replaceAll("");
    return slug.toLowerCase(Locale.ENGLISH);
  }

This is still a fairly naive process, though. It isn’t going to do anything for s-sharp (ß – used in German), or any non-Latin-based alphabet (Greek, Cyrillic, CJK, etc).

Be careful when changing the case of a string. Upper and lower case forms are dependent on alphabets. In Turkish, the capitalization of U+0069 (i) is U+0130 (İ), not U+0049 (I) so you risk introducing a non-latin1 character back into your string if you use String.toLowerCase() under a Turkish locale.