private void validateAuthenticationInfo(Hashtable<String, Object> environment)
        throws AuthenticationException
    {
        // validate when using Simple auth both principal and credentials are set
        if(SIMPLE_AUTHENTICATION_MECHANISM_NAME.equals(environment.get(Context.SECURITY_AUTHENTICATION))) {

            // only validate credentials if we have a non-empty principal
            if( environment.get(Context.SECURITY_PRINCIPAL) != null &&
                StringUtils.hasText( String.valueOf( environment.get(Context.SECURITY_PRINCIPAL) ))) {

                Object credentials = environment.get(Context.SECURITY_CREDENTIALS);

                // from the FAQ, we need to check for empty credentials:
                // http://docs.oracle.com/javase/tutorial/jndi/ldap/faq.html
                if( credentials == null ||
                    (credentials instanceof byte[] && ((byte[])credentials).length <= 0) || // empty byte[]
                    (credentials instanceof char[] && ((char[])credentials).length <= 0) || // empty char[]
                    (String.class.isInstance(credentials) && !StringUtils.hasText(String.valueOf(credentials)))) {

                    throw new javax.naming.AuthenticationException("LDAP Simple authentication requires both a "
                                                                       + "principal and credentials.");
                }
            }
        }
    }

}