Fetching DNS MX and A records

The following code works fine, but it requires hard coding in a DNS
server IP or name. I vaguely recall there is a new way to do this
where it finds a DNS server on its own, or there is a new method to
dynamically find a DNS server.

  /**
     * Gets all matching dns records as an array of strings.
     *
     * @param domain domain, e.g. oberon.ark.com or oberon.com which
you want
     * the DNS records.
     * @param types e.g."MX","A" to describe which types of
     * record you want.
     *
     * @return ArrayList of Strings
     *
     * @throws NamingException if DNS lookup fails.
     */
    private static ArrayList<String> getDNSRecs( String domain,
                                                 String... types )
throws NamingException
        {
        ArrayList<String> results = new ArrayList<String>( 15 );
        DirContext ictx = new InitialDirContext();
        Attributes attrs =
                ictx.getAttributes( "dns://" + DNS_SERVER + "/" +
domain,
                                    types );
        for ( Enumeration e = attrs.getAll(); e.hasMoreElements(); )
            {
            Attribute a = (Attribute) e.nextElement();
            int size = a.size();
            for ( int i = 0; i < size; i++ )
                {
                // MX string has priority (lower better) followed by
associated mailserver
                // A string is just IP
                results.add( (String) a.get( i ) );
                }// end inner for
            }// end outer for
        if ( DEBUGGING && results.size() == 0 )
            {
            System.err.println( "Failed to find any DNS records for
domain " + domain );
            }
        return results;
        }
--

Roedy Green Canadian Mind Products
The Java Glossary
http://mindprod.com