域对象的引用，ActionContext 和ServletActionContext类的使用

ActionContext 获取 域引用的map

ServletActionContext获取具体域对象

//域范围

        ActionContext ac = ActionContext.getContext();
        Map<String,Object> applicationMap = ac.getApplication();//这个就是ServletContext对象中维护的那个Map
        applicationMap.put("p", "application_p");// ServletContext.setAttribute(key,object);

        Map<String,Object> sessionMap = ac.getSession();//这个就是HttpSession对象中维护的那个Map
        sessionMap.put("p", "session_p");// HttpSession.setAttribute(key,object);

        ac.put("p", "request_p");//相当于ServletRequest.setAttribute(key,obj);

 //获取Servlet中的常用对象的引用

 //ServletContextAware接口

 public class WebObjectAction extends ActionSupport implements Serializable,ServletContextAware,ServletRequestAware,ServletResponseAware {
     private ServletContext context;
     private HttpServletRequest request;
     private HttpServletResponse response;
     //方式一
     public String execute1(){
         ServletContext sc = ServletActionContext.getServletContext();
         System.out.println(sc);
         ServletRequest request = ServletActionContext.getRequest();
         System.out.println(request);
         return SUCCESS;
     }
     //方式二
     public String execute2(){
         System.out.println(context);
         System.out.println(request);
         System.out.println(response);
         return SUCCESS;
     }
     public void setServletContext(ServletContext context) {//如果动作类实现了ServletContextAware接口，就会自动调用该方法
         this.context = context;
     }
     public void setServletRequest(HttpServletRequest request) {
         this.request = request;
     }
     public void setServletResponse(HttpServletResponse response) {
         this.response = response;
     }

 }