登录功能的简单实现

我会带着你远行 2023-07-08 05:55 34阅读 0赞

**1. 功能描述**

*  输入用户名、密码、验证码进行登录（[关于验证码的实现点这里][Link 1]）
 *  如果用户名和密码输入有误，跳转到登录页面，并提示:用户名或密码错误
 *  如果验证码输入有误，跳转到登录页面，并提示：验证码错误
 *  全部输入正确，显示：用户名，欢迎您

**2. 简单分析**

*  编写登录页面
 *  使用 Druid 数据库连接池技术，操作数据库中存用户信息的表user
 *  先判断验证码输入是否正确
 *  验证码输入正确，再判断用户名和密码输入是否正确
 *  需要的jar包自取：  
    [链接][Link 2]：https://pan.baidu.com/s/1OjGY4FxoZQ08ogDbCW4GHQ  
    提取码：piyf  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0F1Z2Vuc3Rlcm5f_size_16_color_FFFFFF_t_70]

**3. 代码及步骤**

*  创建数据库login并创建user表

CREATE DATABASE login;
    USE login;
    CREATE TABLE user(
    	id INT PRIMARY KEY AUTO_INCREMENT,
    	username VARCHAR(32) UNIQUE NOT NULL,
    	password VARCHAR(32) NOT NULL
    	);

*  创建用户的实体类

package domain;
    
    /**
     * 用户的JavaBean
     */
    public class User {
        
        private int id;
        private String username;
        private String 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;
        }
    
    }

*  编写配置文件，并使用Druid数据库连接池技术，编写JDBC工具类

**配置文件druid.properties**

driverClassName=com.mysql.jdbc.Driver
    url=jdbc:mysql://localhost:3306/login
    username=XXX
    password=XXX
    initialSize=5
    maxActive=10
    maxWait=3000

**JDBC工具类**

package util;
    
    import com.alibaba.druid.pool.DruidDataSourceFactory;
    
    import javax.sql.DataSource;
    import java.io.InputStream;
    import java.sql.Connection;
    import java.sql.SQLException;
    import java.util.Properties;
    
    /**
     * JDBC工具类
     */
    public class JDBCUtils {
        
         private static DataSource ds;
    
        static {
        
            try {
        
                //1.加载配置文件
                Properties pro = new Properties();
                InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");
                pro.load(is);
                //2.初始化连接池对象
                ds = DruidDataSourceFactory.createDataSource(pro);
            } catch (IOException e) {
        
                e.printStackTrace();
            } catch (Exception e) {
        
                e.printStackTrace();
            }
        }
    
        /**
         * 获取连接池对象
         */
        public static DataSource getDataSource(){
        
            return ds;
        }
    
        /**
         * 获取连接Connection对象
         */
        public static Connection getConnection() throws SQLException {
        
            return ds.getConnection();
        }
    }

*  创建类UserDao,提供login方法

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;
    
    /**
     * 操作数据库中User表的类
     */
    public class UserDao {
        
        private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());
    
        public User login(User loginUser){
        
            try {
        
                String sql = "select * from user where username=? and password=?";
                User user = template.queryForObject(sql,
                        new BeanPropertyRowMapper<User>(User.class),
                        loginUser.getUsername(),loginUser.getPassword());
                return user;
            } catch (DataAccessException e) {
        
                e.printStackTrace();
                return null;
            }
        }
    }

*  动态生成验证码

package 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 java.awt.*;
    import java.awt.image.BufferedImage;
    import java.io.IOException;
    import java.util.Random;
    
    /**
     * 验证码
     */
    @WebServlet("/CheckCodeServlet")
    public class CheckCodeServlet extends HttpServlet {
        
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
            int width = 100;
            int height = 50;
    
            //1."创建"验证码图片
            BufferedImage image = new BufferedImage(width,height, BufferedImage.TYPE_INT_RGB);
    
            //2."画"验证码
            Graphics g = image.getGraphics();//画笔对象
            g.setColor(Color.orange);//设置画笔颜色
            g.fillRect(0,0,width,height);//填充背景色
            g.setColor(Color.red);
            g.drawRect(0,0,width-1,height-1);//画边框
    
            //"写验证码"
            String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
            Random ran = new Random();
            StringBuilder s = new StringBuilder();
            for(int i = 1; i <= 4; i++){
        
                int index = ran.nextInt(str.length());//获取随机角标
                char ch = str.charAt(index);
                s.append(ch);
                g.drawString(ch+"",width/5*i,height/2);//"写验证码"
            }
            String checkCode_session = s.toString();
            request.getSession().setAttribute("checkCode_session",checkCode_session);//将生产的验证码存入session
    
            //"画"干扰线
            g.setColor(Color.gray);
            for(int i = 0; i < 10; i++){
        
                int x1 = ran.nextInt(width);
                int x2 = ran.nextInt(width);
                int y1 = ran.nextInt(height);
                int y2 = ran.nextInt(height);
                g.drawLine(x1,y1,x2,y2);
            }
    
            //3.将验证码输出到页面展示
            ImageIO.write(image,"jpg",response.getOutputStream());
        }
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
            this.doPost(request, response);
        }
    }

*  登录的Servlet

package 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.HashMap;
    import java.util.Map;
    
    @WebServlet("/LoginServlet")
    public class LoginServlet extends HttpServlet {
        
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
            request.setCharacterEncoding("utf-8");//设置编码
            //获取参数
            String checkCode = request.getParameter("checkCode");//用户输入的验证码
            Map map = new HashMap<>(request.getParameterMap());
            map.remove("checkCode");
            User loginUser = new User();
            try {
        
                BeanUtils.populate(loginUser,map);
            } catch (IllegalAccessException e) {
        
                e.printStackTrace();
            } catch (InvocationTargetException e) {
        
                e.printStackTrace();
            }
    
            //先判断验证码是否正确
            HttpSession session = request.getSession();
            String checkCode_session = (String)session.getAttribute("checkCode_session");//自动生成的验证码
            session.removeAttribute("checkCode_session");//删除session中存储的验证码，保证只能用一次
            //忽略大小写判断
            if(checkCode_session!=null && checkCode_session.equalsIgnoreCase(checkCode)){
        //验证码一致
                //判断用户名、密码是否正确
                UserDao dao = new UserDao();
                User user = dao.login(loginUser);
                if(user==null){
        //登录失败
                    request.setAttribute("login_error","用户名或密码错误");
                    request.getRequestDispatcher("/login.jsp").forward(request,response);//转发到登录页面
                }else {
        //登录成功
                    session.setAttribute("user",user);//存储用户信息
                    response.sendRedirect(request.getContextPath()+"/SuccessServlet");//重定向到SuccessServlet
                }
            }else {
        //验证码不一致
                request.setAttribute("checkCode_error","验证码错误");//存储提示信息到request
                request.getRequestDispatcher("/login.jsp").forward(request,response);//转发到登录页面
            }
        }
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
            this.doPost(request, response);
        }
    }

*  登录成功的Servlet

package servlet;
    
    import domain.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;
    
    @WebServlet("/SuccessServlet")
    public class SuccessServlet extends HttpServlet {
        
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
            HttpSession session = request.getSession();
            User user = (User)session.getAttribute("user");
            if(user != null){
        
                response.setContentType("text/html;charset=utf-8");
                response.getWriter().write("<h2>登录成功！"+user.getUsername()+"欢迎您</h1>");
            }
        }
    
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
            this.doPost(request, response);
        }
    }

*  登录页面（html、jsp都可以）

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
      <head>
        <title>首页</title>
        <script>
          window.onload = function () {
        
            var img = document.getElementById("img");
            img.onclick = function () {
        
              this.src = "${pageContext.request.contextPath}/CheckCodeServlet?time="+new Date().getTime();
            }
            document.getElementById("change").onclick = img.onclick;
          }
        </script>
        <style>
          div{
        
            color: red;
          }
        </style>
      </head>
      <body>
        <form action="${pageContext.request.contextPath}/LoginServlet" method="post">
          <table>
            <tr>
              <td>用户名：</td>
              <td><input type="text" name="username" placeholder="请输入用户名"></td>
            </tr>
            <tr>
              <td>密码：</td>
              <td><input type="password" name="password" placeholder="请输入密码"></td>
            </tr>
            <tr>
              <td>验证码：</td>
              <td><input type="text" name="checkCode"></td>
            </tr>
            <tr>
              <td colspan="2">
                <img id="img" src="${pageContext.request.contextPath}/CheckCodeServlet">
                <a id="change" href="">看不清？换一张</a>
              </td>
            </tr>
            <tr align="center">
              <td colspan="2"><input type="submit" value="登录"></td>
            </tr>
          </table>
        </form>
        <%--如果用户名、密码或验证码输入错误，显示提示信息--%>
        ${
        requestScope.checkCode_error}
        ${
        requestScope.login_error}
      </body>
    </html>

[Link 1]: https://blog.csdn.net/Augenstern_/article/details/104494368
[Link 2]: https://pan.baidu.com/s/1OjGY4FxoZQ08ogDbCW4GHQ
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0F1Z2Vuc3Rlcm5f_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20200225120719714.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0F1Z2Vuc3Rlcm5f,size_16,color_FFFFFF,t_70