Session & Cookie登录案例 January 27，2020

 ## 案例：验证码

1. 案例需求：
　　1. 访问带有验证码的登录页面login.jsp
2. 用户输入用户名，密码以及验证码。
　　* 如果用户名和密码输入有误，跳转登录页面，提示:用户名或密码错误
　　* 如果验证码输入有误，跳转登录页面，提示：验证码错误
　　* 如果全部输入正确，则跳转到主页success.jsp，显示：用户名,欢迎您

2. 分析：

　　

package domain;
/**
 * 用户 实体类
 */
public class User {
        private int id;
        private String username;
        private String password;

        public User() {
        }

        public User(int id, String username, String password) {
            this.id = id;
            this.username = username;
            this.password = password;
        }

        public int getId() {
            return id;
        }

        public void setId(int id) {
            this.id = id;
        }

        public String getUsername() {
            return username;
        }

        public void setUsername(String username) {
            this.username = username;
        }

        public String getPassword() {
            return password;
        }

        public void setPassword(String password) {
            this.password = password;
        }

        @Override
        public String toString() {
            return "User{" +
                    "id=" + id +
                    ", username='" + username + '\'' +
                    ", password='" + password + '\'' +
                    '}';
        }

}

package util;

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;

/**
 * JDBC工具类 druid
 */
public class JDBCUtils {
    private static DataSource ds;
    static {
        try {
            //1.加载配置文件
            Properties properties = new Properties();
            //使用ClassLoader加载配置文件，获取字节输入流
            InputStream resourceAsStream = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");
            properties.load(resourceAsStream);
            //2.初始化连接池对象
            ds = DruidDataSourceFactory.createDataSource(properties);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
    /**
     * 获取Connection对象
     */
    public static Connection getConnection() throws SQLException {
        return ds.getConnection();
    }

    /**
     * 获取连接池对象
     */
    public static DataSource getDataSource(){
        return ds;
    }
}

package dao;

import domain.User;
import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import util.JDBCUtils;

/**
 * 操作数据库User表的类
 * */
public class UserDao {
    //声明JDBCTemplate对象共用
    private JdbcTemplate jdbcTemplate = new JdbcTemplate(JDBCUtils.getDataSource());
    /**
     * 登录方法
     * @param loginUser 只有用户和密码
     * @return user返回用户的所有信息
     */
    public User login(User loginUser){
        try {
            String sql = "select * from user where username=? and password = ?";
            //将查询的结果封装为USER
            User user = jdbcTemplate.queryForObject(sql,
                    new BeanPropertyRowMapper<User>(User.class),
                    loginUser.getUsername(), loginUser.getPassword());
            return user;
        } catch (DataAccessException e) {
            e.printStackTrace();
            return null;
        }
    }
}

package web.servlet;

import javax.imageio.ImageIO;
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.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

/**
    验证码 案例
 */
@WebServlet( "/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.创建一个对象，在内存中 存放图片
        int width = 100;
        int heigth = 50;
        BufferedImage image = new BufferedImage(width,heigth,BufferedImage.TYPE_INT_RGB);
        //2.美化图片
            //2.1填充背景色
        Graphics graphics = image.getGraphics();//画笔对象
        graphics.setColor(Color.PINK);//设置画笔颜色
        graphics.fillRect(0,0,width,heigth);//填充矩形
            //2.2画边框
        graphics.setColor(Color.BLUE);
        graphics.drawRect(0,0,width-1,heigth-1);//因为画笔有1px  所以要减一
            //2.3填写验证码
        String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

        StringBuilder img_str = new StringBuilder();//用来存储验证码信息
        Random random = new Random();
        for (int i = 1; i <=4 ; i++) {
            int index = random.nextInt(str.length());
            graphics.drawString(str.charAt(index)+"",width/5*i,heigth/2);
            img_str.append(str.charAt(index));
        }
        HttpSession session = request.getSession();
        session.setAttribute("checkCode_session",img_str.toString());
        //2.4画干扰线
        graphics.setColor(Color.green);
        for (int i = 0; i <10 ; i++) {
            int x1 = random.nextInt(width);
            int x2 = random.nextInt(width);
            int y1 = random.nextInt(heigth);
            int y2 = random.nextInt(heigth);
            graphics.drawLine(x1,y1,x2,y2);
        }
        //3.将图片输出至页面展示
        ImageIO.write(image,"jpg",response.getOutputStream());

    }

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

package web.servlet;

import dao.UserDao;
import domain.User;
import org.apache.commons.beanutils.BeanUtils;

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.lang.reflect.InvocationTargetException;
import java.util.Map;

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.设置编码
        request.setCharacterEncoding("utf-8");
        //2.获取请求参数
        String login_username = request.getParameter("username");
        String login_password = request.getParameter("password");
        String login_checkCode = request.getParameter("checkCode");
        //3.获取验证码
        HttpSession session = request.getSession();
        String  checkCode_session = (String) session.getAttribute("checkCode_session");
        //删除session中存储的验证码
        session.removeAttribute("checkCode_session");

        //4.判断验证码是否正确 忽略大小写比较
        if(login_checkCode!=null && checkCode_session.equalsIgnoreCase(login_checkCode)){
            //5.验证码正确 判断账号与密码是否正确
            User loginUser = new User();
            loginUser.setUsername(login_username);
            loginUser.setPassword(login_password);
            UserDao userDao = new UserDao();
            User user = userDao.login(loginUser);
            if(user==null){
                //登录失败
                //存储提示信息到request
                request.setAttribute("login_error","用户名或密码错误");
                //转发到登录页面
                request.getRequestDispatcher("/login.jsp").forward(request,response);
            }else{
                //登录成功
                // 存储信息，用户信息  因为User信息可能跨越很多页面，所以使用session而不使用request
                session.setAttribute("user",user.getUsername());
                //重定向到success.jsp
                response.sendRedirect(request.getContextPath()+"/success.jsp");
            }
        }else{
            request.setAttribute("cc_error","验证码错误");
            //验证码错误
            request.getRequestDispatcher("login.jsp").forward(request,response);
        }

    }

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

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>登录案例</title>
    <!--
    分析：
        点击图片，需要换一张
            1.给超链接和图片绑定单击事件
            2.重新设置图片的src属性值
    -->
    <script>
        window.onload = function () {
            document.getElementById("img").onclick= function () {
                this.src = "${pageContext.request.contextPath}/checkCodeServlet?"+new Date().getTime();
            }
        }
    </script>
</head>
<body>
        <form action="${pageContext.request.contextPath}/loginServlet" method="post">
            <table>
                <tr>
                    <td>用户名</td>
                    <td><input type="text" placeholder="请输入用户名" name="username"></tr></td>
                <tr>
                    <td>密码</td>
                    <td><input type="text" placeholder="请输入用户密码" name="password"></td>
                </tr>
                <tr >
                    <td>验证码</td>
                    <td><input type="text" placeholder="请输入验证码" name="checkCode"></td>
                </tr>
                <tr>
                    <td colspan="2"><img id="img" src="${pageContext.request.contextPath}/checkCodeServlet"></td>
                </tr>
                <tr>
                    <td colspan="2"><input type="submit" value="登录"></td>
                </tr>
            </table>
        </form>
        ${requestScope.cc_error}
        ${requestScope.login_error}

</body>
</html>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>登录成功页面</title>
</head>
<body>
    <%
        HttpSession session1 = request.getSession();
        String user = (String) session1.getAttribute("user");
        out.print(user+"欢迎登录");
    %>
</body>
</html>