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);
     }