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;

     }

 }