private Object[] getUserPass() throws LoginException {
      NameCallback nameCB = new NameCallback("username");
      PasswordCallback passwordCB = new PasswordCallback("password", false);

      try {
        callbackHandler.handle(new Callback[] {nameCB, passwordCB});
      } catch (IOException | UnsupportedCallbackException e) {
        throw new LoginException(e.toString());
      }

      String username = nameCB.getName();
      char[] password = passwordCB.getPassword();
      passwordCB.clearPassword();
      return new Object[] {username, password};
    }