/** Converting < , > , " and & to their XML entities.
 *  <P>
 *  Taken from Core Servlets and JavaServer Pages
 *  from Prentice Hall and Sun Microsystems Press,
 *  http://www.coreservlets.com/.
 *  &copy; 2000 Marty Hall; may be freely used or adapted.
 */

public class ServletUtilities {
  
  }


  /** Given a string, this method replaces all occurrences of
   *  '<' with '&lt;', all occurrences of '>' with
   *  '&gt;', and (to handle cases that occur inside attribute
   *  values), all occurrences of double quotes with
   *  '&quot;' and all occurrences of '&' with '&amp;'.
   *  Without such filtering, an arbitrary string
   *  could not safely be inserted in a Web page (or XML file).
   */

  public static String filter(String input) {
    StringBuffer filtered = new StringBuffer(input.length());
    char c;
    for(int i=0; i<input.length(); i++) {
      c = input.charAt(i);
      if (c == '<') {
        filtered.append("&lt;");
      } else if (c == '>') {
        filtered.append("&gt;");
      } else if (c == '"') {
        filtered.append("&quot;");
      } else if (c == '&') {
        filtered.append("&amp;");
      } else {
        filtered.append(c);
      }
    }
    return(filtered.toString());
  }
}