请求调用session.invalidate()后,request.getSession(false)不返回null

Question

不应该使会话无效导致request.getSession(false)返回null吗？在我的注销servlet中,我打电话

session.invalidate();

在我的登录状态过滤器中,我打电话

request.getSession(false);

对getSession(false)的调用永远不会返回null,但与返回的会话对象关联的所有属性都为null.我目前通过搜索空属性来检测用户是否已注销,但这似乎不正确.

Answer 1

我目前通过搜索空属性来检测用户是否已注销

这也是正常的做法.要检查用户是否已登录,您肯定不会检查servletcontainer是否已创建会话.这根本不代表登录用户.

登录时,只需将用户模型对象放在会话范围中,而不检查容器是否为您创建了会话.换句话说,只使用getSession()不带布尔参数,以便容器在必要时自动创建,无论如何您都需要会话:

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    User user = userService.find(username, password);

    if (user != null) {
        request.getSession().setAttribute("user", user);
        response.sendRedirect(request.getContextPath() + "/home");
    } else {
        request.setAttribute("message", "Unknown login. Please retry.");
        request.getRequestDispatcher("/WEB-INF/login.jsp").forward(request, response);
    }
}

在访问过滤,只检查是否代表已登录用户的会话属性存在,你只用getSession(false)在这里,以避免不必要的会话创建,否则例如searchbots会触发会话创建这是完全没有必要的:

@Override
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
    HttpServletRequest request = (HttpServletRequest) req;
    HttpServletResponse response = (HttpServletResponse) res;
    HttpSession session = request.getSession(false);
    User user = (session != null) ? (User) session.getAttribute("user") : null;
    String loginURL = request.getContextPath() + "/login"; 

    if (user == null && !request.getRequestURI().equals(loginURL)) {       
        response.sendRedirect(loginURL);
    } else {
        chain.doFilter(request, response);
    }
}

注销时,请确保在invalidate之后发送重定向,因为当前会话仍然可以在转发的响应中使用.

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    request.getSession().invalidate();
    response.sendRedirect(request.getContextPath() + "/login");
}