code: public static FacesMessage getMessage(FacesMessage.Severity severity,
                                            String messageId,
                                            Object arg)
      {
          return getMessage(severity,
                            messageId,
                            new Object[]{arg},
                            FacesContext.getCurrentInstance());
      }
docs: @param severity serverity of message
  @param messageId id of message
  @param arg arument of message
  
  @return generated FacesMessage