当用户未登录时，Servlet 过滤器在无限重定向循环中运行

Question

我有两个 HTML 个文件

login.html
Test.html

我的要求是，用户不应该能够访问 test.html，除非他通过 login.html

成功登录

这是我的 login.html 文件

<html>
<head>
<title>Login Page 122</title>
</head>
<body>
<form action="LoginServlet" method="post">
Username: <input type="text" name="user">
<br>
Password: <input type="password" name="pwd">
<br>
<input type="submit" value="Login User">
</form>
</body>
</html>

这是我的 LoginServlet，它在单击提交按钮时接收请求

package com;
public class LoginServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private final String userID = "admin";
    private final String password = "password";

    protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {

        String user = request.getParameter("user");
        String pwd = request.getParameter("pwd");

        if(userID.equals(user) && password.equals(pwd)){
            HttpSession session = request.getSession();
            session.setAttribute("user", "LoggedIN");
            response.sendRedirect("LoginSuccess.jsp");
        }else{
            RequestDispatcher rd = getServletContext().getRequestDispatcher("/login.html");
            PrintWriter out= response.getWriter();
            out.println("<font color=red>Either user name or password is wrong.</font>");
            rd.include(request, response);
        }

    }

}

这是我的过滤器 class，它保护 *.html 资源

package com;
 public class AuthenticationFilter implements Filter {
    private ServletContext context;
    public void init(FilterConfig fConfig) throws ServletException {
        this.context = fConfig.getServletContext();
        this.context.log("AuthenticationFilter initialized");
    }
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest) request;
        HttpServletResponse res = (HttpServletResponse) response;
        String uri = req.getRequestURI();
        this.context.log("Requested Resource::"+uri);
        HttpSession session = req.getSession(false);
        if(session == null || !session.getAttribute("user").toString().equals("LoggedIN")){
            this.context.log("Unauthorized access request");
            System.out.println("Into session is null condition");
            res.sendRedirect("login.html");
        }else{
           System.out.println("Into chain do filter");
            chain.doFilter(request, response);
        }
    }
    public void destroy() {
    }
}

这是我的 web.xml 文件

<?xml version="1.0" encoding="UTF-8"?>

<web-app>
  <display-name>LoginFilter</display-name>
   <servlet>
    <description></description>
    <display-name>LoginServlet</display-name>
    <servlet-name>LoginServlet</servlet-name>
    <servlet-class>com.LoginServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>LoginServlet</servlet-name>
    <url-pattern>/LoginServlet</url-pattern>
  </servlet-mapping>
  <servlet>
    <description></description>
    <display-name>LogoutServlet</display-name>
    <servlet-name>LogoutServlet</servlet-name>
    <servlet-class>com.LogoutServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>LogoutServlet</servlet-name>
    <url-pattern>/LogoutServlet</url-pattern>
  </servlet-mapping>
  <filter>
    <display-name>AuthenticationFilter</display-name>
    <filter-name>AuthenticationFilter</filter-name>
    <filter-class>com.AuthenticationFilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>AuthenticationFilter</filter-name>
    <url-pattern>*.html</url-pattern>
  </filter-mapping>
</web-app>

我看到的问题是

我在我的服务器控制台中多次看到此语句。

Into session is null condition
Into session is null condition
Into session is null condition
Into session is null condition
Into session is null condition
Into session is null condition
Into session is null condition
Into session is null condition
Into session is null condition
Into session is null condition
Into session is null condition
Into session is null condition
Into session is null condition

Answer 1

此 AuthenticationFilter 也会在请求 login.html 时运行。但是，代码再次重定向到 login.html 而不是继续过滤器链。这解释了无限重定向循环。

如果当前请求的页面已经是登录页面本身，您需要让过滤器继续请求。

例如

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
    HttpServletRequest req = (HttpServletRequest) request;
    HttpServletResponse res = (HttpServletResponse) response;
    HttpSession session = req.getSession(false);
    String loginURL = req.getContextPath() + "/login.html";

    boolean loggedIn = session != null && session.getAttribute("user") != null;
    boolean loginRequest = loginURL.equals(req.getRequestURI());

    if (loggedIn || loginRequest) {
        chain.doFilter(request, response);
    } else {
        res.sendRedirect(loginURL);
    }
}

另请参阅：

Authentication filter and servlet for login

当用户未登录时，Servlet 过滤器在无限重定向循环中运行

Servlet filter runs in infinite redirect loop when user is not logged in

servlets

login

servlet-filters

redirect-loop

另请参阅：