session.put("user", user);//user为一个bean对象
JSP界面判断session是否为空:
<s:if test="#session.user==null "><a href="adminLogin.jsp" >登录</a> </s:if> <s:if test="#session.user!=null"> welcome[<a href="javascript:void(0);" onclick="displayUserInfo()"> <span id="userAccount"><s:property value="#session.user.userAccount" /></span></a>] <a href="javascript:void(0)" onclick="logout()"><img src="../img/logout.png" width="16px" height="16px" alt="退出" /></a> </s:if>