}
@Override
public void writeAppUser(AppUser appUserIn) throws IllegalArgumentException
{
AppUser appUser = ObjectifyService.ofy().load().type(AppUser.class).id(appUserIn.id).now();
if (appUser != null)
{
if (!Utils.isEmpty(appUserIn.AndroidKey))
{
AppUser other = ObjectifyService.ofy().load().type(AppUser.class).filter("AndroidKey", appUserIn.AndroidKey).first().now();
if (other != null)
{
if (other.id != appUser.id)
{
throw new IllegalArgumentException("Android API Key is already used by another user!");