docs: @Override
      public void handle ( Callback[] callbacks ) throws IOException, UnsupportedCallbackException {
          for ( Callback cb : callbacks ) {
              if ( log.isDebugEnabled() ) {
                  log.debug("Got callback " + cb.getClass().getName());
              }
  
              if ( cb instanceof NameCallback ) {
                  NameCallback nc = (NameCallback) cb;
                  String userDomain = this.getSpecifiedUserDomain();
                  if ( this.getUsername() != null && userDomain != null ) {
                      nc.setName(this.getUsername() + "@" + userDomain);
                  }
              }
              else if ( cb instanceof PasswordCallback ) {
                  PasswordCallback pc = (PasswordCallback) cb;
                  if ( this.getPassword() != null ) {
                      pc.setPassword(this.getPassword().toCharArray());
                  }
              }
          }
      }