code: public String getMessage(String key, Locale locale)
  	{
  		if (null == locale)
  		{
  			return getMessage(key);
  		}
  		return CollectionTools.getString(getResourceBundle(locale), key, getBehaviourOnMissingMessage().getValueOnMissingMessage(key));
  	}
docs: /*
  (non-Javadoc)
  
  @see com.sporniket.libre.lang.MessageProviderTrait#getMessage(java.lang.String, java.util.Locale)