信息放进session中以及从session中取出

放进：

ActionContext context = ActionContext.getContext();
HttpServletRequest request = (HttpServletRequest) context.get(ServletActionContext.HTTP_REQUEST);
HttpSession session = request.getSession();
session.setAttribute("user", user);

取出：

ActionContext context = ActionContext.getContext();
HttpServletRequest request = (HttpServletRequest) context.get(ServletActionContext.HTTP_REQUEST);
HttpSession session=request.getSession();
User user=(User) session.getAttribute("user");