private void setLanguage(String lan, HttpServletResponse response, HttpServletRequest request) {
		LocaleResolver localeResolver = checkNotNull(RequestContextUtils.getLocaleResolver(request),
				"No LocaleResolver found!");
		LocaleEditor localeEditor = new LocaleEditor();
		String language = StringUtils.defaultIfBlank(lan,
				config.getControllerProperties().getProperty(PROP_CONTROLLER_DEFAULT_LANG));
		localeEditor.setAsText(language);
		localeResolver.setLocale(request, response, (Locale) localeEditor.getValue());
	}
Return nGrinder index page.

@param user      user
@param exception exception if it's redirected from exception handler
@param region    region. where this access comes from. it's optional
@param model     model
@param response  response
@param request   request
@return "index" if already logged in. Otherwise "login".
ngrinder-controller/src/main/java/org/ngrinder/home/controller/HomeController.java