How to access ThemeDisplay from a bean in liferay?

public ThemeDisplay getThemeDisplay(){
       FacesContext context = FacesContext.getCurrentInstance();
   PortletRequest portletRequest =       (PortletRequest)context.getExternalContext().getRequest();       
   ThemeDisplay themeDisplay = (ThemeDisplay)portletRequest.getAttribute(WebKeys.THEME_DISPLAY);
return themeDisplay;
}