在应用程序正常登录以后，把一些用户相关的身份信息写在Session中，但为了防止恶意用户越权访问，我们还需要在每个页面加载的时候根据用户的当前身份判断他是否有权限打开当前页面。(In the application log, some related to the user identity information written in Session, but in order to prevent malicious users from unauthorized access, we also need when loaded on each page according to the user's current status to determine whether he has permission to open the current page.)