cookie技术自动登录

user

public class User implements Serializable{
    private String username;
    private String nick;
    private String password;
    public User(){}
    
    public User(String username, String nick, String password) {
        super();
        this.username = username;
        this.nick = nick;
        this.password = password;
    }

    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getNick() {
        return nick;
    }
    public void setNick(String nick) {
        this.nick = nick;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    
}

util

md5

import java.security.MessageDigest;

import sun.misc.BASE64Encoder;

public class MD5Util {
    public static String md5(String message){
        try{
            MessageDigest md = MessageDigest.getInstance("md5");
            byte b[] = md.digest(message.getBytes());
            return new BASE64Encoder().encode(b);
        }catch(Exception e){
            throw new RuntimeException(e);
        }
    }
}

 WebUtils

 　　　　//添加Cookie
 1     public static void addAutoLoginFunction(HttpServletRequest request,
            HttpServletResponse response, String username, String password) {
        //把帐号BASE64加密 _ 密码双次md5加密， 所以比较的时候 数据库中密码取出md5加密再和这个比较
        String encodeUsername=new BASE64Encoder().encode(username.getBytes());
        String encodePassword=Md5Util.md5(password);
        System.out.println("存入数据库 帐号:"+username);
        System.out.println("存入数据库 密码:"+password);
        System.out.println("存入Cookie 帐号:"+encodeUsername);
        System.out.println("存入Cookie密码:"+encodePassword);
        Cookie c=new Cookie("loginInfo",encodeUsername+"_"+encodePassword);
        c.setMaxAge(10000);
        c.setPath(request.getContextPath());
        response.addCookie(c);
    }
    //删除Cookie
    public static void removeAutoLoginCookie(HttpServletRequest request,
            HttpServletResponse response) {
        Cookie cs[]=request.getCookies();
        if(cs!=null)
        {
            for(Cookie c:cs)
            {
                if(c.getName().equals("loginInfo"))
                {
                    Cookie cookie=new Cookie("loginInfo",null);
                    cookie.setMaxAge(0);
                    cookie.setPath(request.getContextPath());
                    response.addCookie(cookie);
//                    c.setMaxAge(0);
//                    c.setPath(request.getContextPath());
                    System.out.println("删除Cookie");
                    return;
                }
            }
        }
    }
    

servlet

import sun.misc.BASE64Encoder;
//完成用户登录
public class LoginServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
//        1、取到用户名和密码
        String username = request.getParameter("username");
        String password = request.getParameter("password");
//        2、验证是否正确
        User user = UserDB.findUser(username, password);
        if(user!=null){
    //        3、正确，把用户放到HttpSession中
            request.getSession().setAttribute("user", user);
    //        4、判断用户是否需要自动登录
            String autologin = request.getParameter("autologin");
            if(autologin!=null){

　　　　　　　　　　

    //        5、是：把用户名和密码保存到一个指定的cookie中
                Cookie c = new Cookie("loginInfo",new BASE64Encoder().encode(username.getBytes())+"_"+MD5Util.md5(password));//存在客户端的cookie中，如果密码是名为，很危险
                c.setMaxAge(Integer.MAX_VALUE);
                c.setPath(request.getContextPath());
                response.addCookie(c);
            }
        }
//        6、重定向到主页
        response.sendRedirect(request.getContextPath()+"/autologin/index.jsp");
    }

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

        doGet(request, response);
    }

}

 注销

    private void logout(HttpServletRequest request, HttpServletResponse response) throws IOException {
        WebUtils.removeAutoLoginCookie(request,response);
        request.getSession().invalidate();
        response.sendRedirect(request.getContextPath());
    }

过滤器

public void doFilter(ServletRequest req, ServletResponse resp,
            FilterChain chain) throws IOException, ServletException {
        
        HttpServletRequest request = (HttpServletRequest)req;
        HttpServletResponse response = (HttpServletResponse)resp;
        
        HttpSession session = request.getSession();
        User u = (User)session.getAttribute("user");
        if(u==null){//只有没有登录时才自动登录，已经登录了就不需要了
//            System.out.println("自动登录执行了");
    //        1、获取名称为loginInfo的cookie
            Cookie loginInfoCookie = null;
            Cookie cs[] = request.getCookies();
            for(int i=0;cs!=null&&i<cs.length;i++){
                if("loginInfo".equals(cs[i].getName())){
                    loginInfoCookie = cs[i];
                    break;
                }
            }
            if(loginInfoCookie!=null){
    //        2、有：取出cookie的值：用户名_加密的密码
                String usernamePassword = loginInfoCookie.getValue();// zql_slkdjflksjkfslkfls
    //        3、拆出用户名和密码
                String username = usernamePassword.split("\_")[0];//用户名
                username = new String(new BASE64Decoder().decodeBuffer(username));
                String cookiePassword = usernamePassword.split("\_")[1];//密码
    //        4、再次验证用户名和密码是否正确（根据用户名查出密码，加密后再与cookie中的那个密码进行比对）
                User user = UserDB.findUser(username);
                if(user!=null){
                    //根据用户名查出密码，加密后再与cookie中的那个密码进行比对
                    if(cookiePassword.equals(MD5Util.md5(user.getPassword()))){
        //        5、正确：得到用户对象，放到HttpSession中（自动登录）
                        session.setAttribute("user", user);
                    }
                }
            }
        }
        //放行
        chain.doFilter(request, response);
    }