Struts2访问或添加元素

1、完全脱离ServletAPI
    ActionContext acx = ActionContext.getContext();
acx.put("request1", "request");
acx.getApplication().put("application1","application");
acx.getSession().put("session1", "session");
  依靠拦截器的核心功能实现Map与request,session,application之间的转化

2、得到HttpRequest,ServletContex,HttpResponse对象
    a.借助ServletActionContext
   HttpServletRequest request = ServletActionContext.getRequest();
HttpSession session = request.getSession();
        ServletContext application =      ServletActionContext.getServletContext();
    HttpServletResponse response = ServletActionContext.getResponse();
   b.DI(IOC)
   Action实现ServletRequestAware,ServletResponseAware,ServletContextAware接口
提供HttpServletRequest,HttpServletResponse,ServletContext属性