5 Cookie和Session案例开发

案例:通过HttpSession判断用户是否登录

需求:实现登录一次即可,在一次会话内,可以反复多次访问WEB-INF/ welcome.html,如果没有登录过,跳转到登录页,登录成功后,可以访问

项目结构:

组件介绍:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<form method="get" action="loginServlet.do">
    用户名:<input type="text" name="username" ><br/>
    密码:<input type="password" name="password" ><br/>
    <input type="submit" >
</form>
</body>
</html>

登录成功之后可以访问的资源

main.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
   this is main page
</body>
</html>

LoginServlet

用来校验登录的,登录成功将用户信息存户HttpSession,否则回到登录页

package com.msb.servlet;
import com.msb.pojo.User;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
/**
 * @Author: Ma HaiYang
 * @Description: MircoMessage:Mark_7001
 */
@WebServlet(urlPatterns = "/loginServlet.do")
public class LoginServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 获取用户名和密码
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        // 如果用户名和密码为 msb 1234
        if("msb".equals(username)  && "1234".equals(password)){
            // 将用户信息放在HTTPSession中
            User user =new User(null, null, "msb", "1234");
            HttpSession session = req.getSession();
            session.setAttribute("user", user);
            // 登录成功 跳转至 main.html
            resp.sendRedirect(req.getContextPath()+"/mainServlet.do");
        }else{
            // 登录失败 回到login.html
            resp.sendRedirect(req.getContextPath()+"/login.html");
        }
    }
}

MainServlet

用来向main.html中跳转的,同时验证登录,登录过,可以直接跳转,否则回到登录页

package com.msb.servlet;
import com.msb.pojo.User;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.util.logging.Handler;
/**
 * @Author: Ma HaiYang
 * @Description: MircoMessage:Mark_7001
 */
@WebServlet(urlPatterns = "/mainServlet.do")
public class MainServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //跳转至main.html
        HttpSession session = req.getSession();
        User user = (User)session.getAttribute("user");
        if(null != user){
            // 判断如果登录过 允许跳转  HTTPSession中如果有登陆过的信息
            req.getRequestDispatcher("/WEB-INF/main.html").forward(req,resp);
        }else{
            // 如果没有登录过 回到登录去登录  HTTPSession中如果有登陆过的信息
            resp.sendRedirect("login.html");
        }
    }
}

User

用来存储一个用户的信息的实体类对象

public class User implements Serializable {
    private Integer uid;
    private String realname;
    private String username;
    private String pasword;