code: public void handle(Callback[] callbacks) throws IOException, UnsupportedCallbackException {
          for (Callback c : callbacks) {
              if (c instanceof NameCallback) {
                  LOG.debug("name callback");
              } else if (c instanceof PasswordCallback) {
                  LOG.debug("password callback");
                  LOG.warn("Could not login: the client is being asked for a password, but the "
                          + " client code does not currently support obtaining a password from the user."
                          + " Make sure that the client is configured to use a ticket cache (using"
                          + " the JAAS configuration setting 'useTicketCache=true)' and restart the client. If"
                          + " you still get this message after that, the TGT in the ticket cache has expired and must"
                          + " be manually refreshed. To do so, first determine if you are using a password or a"
                          + " keytab. If the former, run kinit in a Unix shell in the environment of the user who" + " is running this client using the command"
                          + " 'kinit <princ>' (where <princ> is the name of the client's Kerberos principal)." + " If the latter, do"
                          + " 'kinit -k -t <keytab> <princ>' (where <princ> is the name of the Kerberos principal, and"
                          + " <keytab> is the location of the keytab file). After manually refreshing your cache,"
                          + " restart this client. If you continue to see this message after manually refreshing"
                          + " your cache, ensure that your KDC host's clock is in sync with this host's clock.");
              } else if (c instanceof AuthorizeCallback) {
                  LOG.debug("authorization callback");
                  AuthorizeCallback ac = (AuthorizeCallback) c;
                  String authid = ac.getAuthenticationID();
                  String authzid = ac.getAuthorizationID();
                  if (authid.equals(authzid)) {
                      ac.setAuthorized(true);
                  } else {
                      ac.setAuthorized(false);
                  }
                  if (ac.isAuthorized()) {
                      ac.setAuthorizedID(authzid);
                  }
              } else {
                  throw new UnsupportedCallbackException(c);
              }
          }
      }
docs: This method is invoked by SASL for authentication challenges
  
  @param callbacks a collection of challenge callbacks