How to get the username for a custom link

$current_user = get_userdata( get_current_user_id() );
echo 'http://www.mywebsite.myweb/storefront/' . $current_user->user_login;

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)