登录页面JDBC案例

以你之姓@ 2024-03-31 12:16 68阅读 0赞

## 登录页面底层逻辑原理 ##

简介：本文讲解，登录页面网页之下，如何使用java来设计账号的登录，与账号的注册的底层实现。

### 文件结构 ###

![在这里插入图片描述][96649fc5b6574d8e8525533f34e6fe66.png]

### User类 ###

package com.study;
    
    public class User {
        
        private String username;
        private String password;
    
        public User(String username, String password) {
        
            this.username = username;
            this.password = password;
        }
    
        public User() {
        
        }
    
        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;
        }
    }

## druid.properties配置文件 ##

driverClassName=com.mysql.cj.jdbc.Driver
    url=jdbc:mysql://localhost:3306/db?serverTimezone=GMT%2B8&useOldAliasMetadataBehavior=true
    username=root
    password=12345
    # ???????
    initialSize=5
    # ?????
    maxActive=10
    # ??????
    maxWait=3000

### Login ###

package com.study;
    
    import com.alibaba.druid.pool.DruidDataSourceFactory;
    
    import javax.sql.DataSource;
    import java.io.FileInputStream;
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Properties;
    import java.util.Scanner;
    
    public class Login {
        
    
        // 查询所有用户
        public static ArrayList<User> SelectAll(Connection conn) throws Exception {
        
            //2. 定义SQL
            String sql = "select * from users;";
            //3. 获取pstmt对象
            PreparedStatement pstmt = conn.prepareStatement(sql);
            //4. 设置参数
            //5. 执行SQL
            ResultSet rs = pstmt.executeQuery();
            //6. 处理结果 List<User> 封装User对象，装载List集合
            User user = null;
            ArrayList<User> users = new ArrayList<>();
    
            while (rs.next()){
        
                // 获取数据
                String username = rs.getString("username");
                String userpwd = rs.getString("userpwd");
    //            System.out.println(username + " " + userpwd);
    
                users.add(new User(username, userpwd)); // 每次都需要创建一个新对象
                // 不然就是浅拷贝了 会导致每次的数据一样的
            }
    //         System.out.println(users);
    //        System.out.println(users.size());
            //7. 释放资源
            rs.close();
            pstmt.close();
            return users;
        }
    
        public static void Add(Connection conn, User user) throws Exception {
        
            // 接收页面提交的参数
            String username = user.getUsername();
            String password = user.getPassword();
    
            //2. 定义SQL
            String sql = "insert into users(username, userpwd) values(?,?);";
            //3. 获取pstmt对象
            PreparedStatement pstmt = conn.prepareStatement(sql);
            //4. 设置参数
            pstmt.setString(1,username);
            pstmt.setString(2,password);
    
    
            //5. 执行SQL
            int count = pstmt.executeUpdate(); // 影响的行数
            //6. 处理结果
            System.out.println(count > 0);
    
            //7. 释放资源
            pstmt.close();
        }
    
        public static void main(String[] args) throws Exception{
        
            Properties prop = new Properties();
            prop.load(new FileInputStream("src/druid.properties"));
            //4. 获取连接池对象
            DataSource dataSource = DruidDataSourceFactory.createDataSource(prop);
    
            //5. 获取数据库连接 Connection
            Connection conn = dataSource.getConnection();
            ArrayList<User> users = SelectAll(conn);
    
            boolean flag = false; // 判断是否登录成功
            System.out.println("首先演示登录");
            Scanner in = new Scanner(System.in);
            System.out.print("请输入你的账号：");
            String username = in.nextLine();
    //        System.out.println(username);
            System.out.print("请输入你的密码：");
            String password = in.nextLine();
    //        System.out.println(password);
            for (int i = 0; i < users.size(); i++) {
        
                User user = users.get(i);
    //            System.out.println(user.getUsername() + " " + user.getPassword());
                if (username.equals(user.getUsername()) && password.equals(user.getPassword())){
        
                    System.out.println("登录成功");
                    flag = true;
                    break;
                }
            }
            if (flag == false){
        
                System.out.println("登录失败");
            }
            System.out.println("现在演示注册");
            System.out.print("请输入你的新账号：");
            username = in.nextLine();
            System.out.print("请输入你的新密码：");
            password = in.nextLine();
            User user = new User(username, password);
            Add(conn, user);
    
        }
    }

[96649fc5b6574d8e8525533f34e6fe66.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/31/02f6b1f643bb4e7193d7983d151dce27.png