9.Action类接收参数(原生的ServletAPI )

 ActionContext(用new ThreadLocal()邦定了线程)
   　　　　|
 　　　　  |--ServletActionContext

        public class ContextAction extends ActionSupport {
            
            public String test(){
                
                //获取request对象
                HttpServletRequest request=ServletActionContext.getRequest();
                request.setAttribute("username", "username_request");
                
                //获取response对象
                HttpServletResponse response=ServletActionContext.getResponse();
                
                //获取session对象
                Map<String,Object> session=ServletActionContext.getContext().getSession();
                session.put("username", "username_session");
                
                //获取ServletContext对象
                ServletContext sc=ServletActionContext.getServletContext();
                sc.setAttribute("username", "username_application");
                
                return "text";
            }
            
        }