public String execute() throws Exception {

         //request域对象==》map (struts2并不推荐使用原生request域对象)

         //不推荐

         Map<String, Object> requestScope = (Map<String, Object>) ActionContext.getContext().get("request");

         //推荐

         ActionContext.getContext().put("name", "requestTom");

         //session域对象==》map

         Map<String, Object> sessionScope = ActionContext.getContext().getSession();

         sessionScope.put("name", "sessionTom");

         //application域对象==》map

         Map<String, Object> applicationScope = ActionContext.getContext().getApplication();

         applicationScope.put("name", "applicationTom");

         return SUCCESS;

     }