使用Servlet自动登录和注销

Question

I want a login application in a Java Servlet. Where I want to automatically login system if the user is previously logged in the site automatically redirect to welcome page instead of login page. All is working fine but when I am clicking on the logout button and set cookies to "" still it doesn't delete the cookie and after logging out it still every time forward me to profile page instead of login page. I am adding here 2 servlets where one contained about redirection mechanism and another is logout servlet. Can anyone please help me to solve my problem?

HomeServlet.java

package com.demo.controller;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;



public class HomeServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public HomeServlet() {
        super();

    }


    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doProcess(request, response);
    }


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


    public void doProcess(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException{
        res.setContentType("text/html");
        PrintWriter out=res.getWriter();  
        System.out.println(req.getCookies());
        Cookie ck[]=req.getCookies();  
        if(ck!=null){  
         String name=ck[0].getValue();  
        if(!name.equals("")||name!=null){  
            res.sendRedirect("ProfileServlet");

        }  
        }else{  
           res.sendRedirect("login");

        }  
    }

}

LogoutServlet.java

package com.demo.controller;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


public class LogoutServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public LogoutServlet() {
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doProcess(request, response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doProcess(request, response);
    }
    protected void doProcess(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();

        Cookie ck=new Cookie("name","");  
        ck.setMaxAge(0);  
        response.addCookie(ck);  

         request.getRequestDispatcher("/login").include(request, response);
         out.println("<script type=\"text/javascript\">");  
         out.println("alert('Logged Out');");  
         out.println("</script>");

         System.out.println("Logout "+ck.getValue() );


    }
}

Answer 1

There may be issue with your if condition...try to debug .

if(!name.equals("")||name!=null){  
            res.sendRedirect("ProfileServlet");

        }  

you can write it eg:

if(name!=null && !name.trim().isEmpty()){  
                res.sendRedirect("ProfileServlet");

 }