JDBC 制作简单的登录验证

    public static void main(String[] args) throws Exception{
        //输入账号密码
        Scanner sc = new Scanner(System.in);
        System.out.println("账号：");
        String zh = sc.next();
        System.out.println("密码：");
        String mm = sc.next();
        //连接到数据库
        zh = zh.replace(‘\‘‘, ‘\"‘);//防止有注入错误
        Class.forName("com.mysql.jdbc.Driver");
        Connection conn=DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/mydb","root","");
        Statement sta = conn.createStatement();
        String sql = "select * from xs where zhanghao=‘"+zh+"‘ and mima=‘"+mm+"‘";//拼接进去但是会有注入错误
        ResultSet rs = sta.executeQuery(sql);  //查询语句
        //输出
        
        if(rs.next()){ //sr.next==true 账号密码输入的符合时
            System.out.println(rs.getString(3)+"登入成功");
        }
        else{  //输入的不符合时
            System.out.println("账号或者密码输入不正确");
        }
        conn.close();        
    }

public static void main(String[] args) throws Exception {
        //输入账号密码
        Scanner sc = new Scanner(System.in);
        System.out.println("账号：");
        String zh = sc.next();
        System.out.println("密码:");
        String mm = sc.next();
        //数据库查询账号密码是否正确
        Class.forName("com.mysql.jdbc.Driver");
        Connection conn = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/mydb", "root", "");

        String sql = "select * from xs where zhanghao=? and mima=?;";
        PreparedStatement sta = conn.prepareStatement(sql);//直接用prepareStatement语句，sql语句可以写在里面；
        sta.setString(1, zh);//第一个?的内容
        sta.setString(2, mm);//第二个?的内容
        ResultSet rs =  sta.executeQuery();//查询语句上面写过sql语句，这里不能写。
        
        //输出
        if(rs.next()){ //sr.next==true 账号密码输入的符合时
            System.out.println(rs.getString(3)+"登入成功");
        }
        else{  //输入的不符合时
            System.out.println("账号或者密码输入不正确");
        }
        conn.close(); 
    }

public static void main2(String[] args) throws Exception{
        Scanner sc = new Scanner(System.in);
        System.out.println("账号：");
        String zh = sc.nextLine();
        System.out.println("密码：");
        String mm = sc.nextLine();
        System.out.println("名称：");
        String xm = sc.nextLine();
        
        Class.forName("com.mysql.jdbc.Driver");
        Connection conn = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/mydb?characterEncoding=GBK","root","");

        String sql = "insert into xs values(?,?,?)";
        PreparedStatement pre = conn.prepareStatement(sql);
        pre.setString(1, zh);
        pre.setString(2, mm);
        pre.setString(3, xm);
        pre.executeUpdate();
        conn.close();
        
    }