管理员和工作人员无法同时登录同一个域但网址不同

如何解决管理员和工作人员无法同时登录同一个域但网址不同

Java 小程序

总共有两个独立的模块，即 Staff 和 Admin
这是他们如何拥有网址

1. http://127.0.0.1:8080/adminLogin
2. http://127.0.0.1:8080/staffLogin

当我以员工身份登录并尝试使用同一浏览器以管理员身份登录时，会抛出以下错误：

HTTP Status 500 – Internal Server Error
Type Exception Report

Description The server encountered an unexpected condition that prevented it from fulfilling the request.

Exception

java.lang.NullPointerException
    package.staff.credentials.session.StaffSession.isstaff(StaffSession.java:57)
    package.staff.credentials.session.StaffSession.isstaffSession(StaffSession.java:36)
    package.staff.site.Template.navbar(Template.java:55)
    package.staff.site.Template.body(Template.java:37)
    package.staff.site.Template.webPage(Template.java:14)
    package.staff.credentials.login.Login.doGet(Login.java:50)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:626)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)

更新
这是代码：

    private static boolean isstaff(HttpServletRequest request) {
        boolean staffSession = false;
        HttpSession session = request.getSession(false);
        int userType = (Integer) session.getAttribute(SessionProperty.userType());
        int valueAsstaff = Integer.parseInt(SessionProperty.userValueAsstaff());
        
        if (userType == valueAsstaff) {
            staffSession = true;
        } else {
            staffSession = false;
        }
    return staffSession;
    }

    private static boolean isSessionValid(HttpServletRequest request) {
        boolean isSessionValid = false;
        HttpSession session = request.getSession(false);
        if (session == null) {
            isSessionValid = false;
        } else {
            isSessionValid = true;
        }
        return isSessionValid;
    }

    public static boolean isstaffSession(HttpServletRequest request) {
        boolean session = false; 
        if(isSessionValid(request)) {
            if(isstaff(request)) {
                session = true;
            }
        }
    return session;
    }