黑马jdbc

Posted 2022-05-17 嫚嫚_

JDBC快速入门

import javax.swing.plaf.nimbus.State;
import java.sql.Connection;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.Statement;

public class jdbcemo 
    public static void main(String[] args) throws Exception 
        //1.注册驱动
        Class.forName("com.mysql.jdbc.Driver");
        //2>获取连接
        String url="jdbc:mysql://127.0.0.1::3306/db1";
        String username ="root";
        String password="1234";
       Connection conn= DriverManager.getConnection(url,username,password);

       //3>定义sql
        String sql="update account set money =2000 where id=1";

        //4获取执行sql的对象statement
       Statement stmt= conn.createStatement();
       //5:执行sql
       int count= stmt.executeUpdate(sql);//受影响的行数//
        //6：处理结果
        System.out.println(count);

        //7:s释放资源
        stmt.close();
        conn.close();


    

sql注入

package com;

import java.sql.*;

public class JDBCuse 
    public static void main(String[] args) throws Exception
        String url="jdbc:mysql://127.0.0.1::3306/db1";
        String username="root";
        String password="1234";


            Connection conn= DriverManager.getConnection(url,username,password);
//接收用户输入  用户名和密码
            String name="张三";
String pws="123";
String sql="selcet *from th_user='"+name+"and password'"+pws+"'";
//执行stmt对象
        Statement stmt=conn.createStatement();
//执行sql
        ResultSet rs=stmt.executeQuery(sql);

        //判断成功与否
        if(rs.next()) 
            System.out.println("登录过程");
        
        else 
            System.out.println("登陆失败");
        
    

package com;

import java.sql.*;

public class JDBCParper 
    public static void main(String[] args) throws Exception
        String url="jdbc:mysql://127.0.0.1::3306/db1";
        String username="root";
        String password="1234";


            Connection conn= DriverManager.getConnection(url,username,password);
//接收用户输入  用户名和密码
            String name="张三";
String pws="123";
//定义sql
        String sql="select * from tb_user where username= ? and password = ?";
        //获取pastmt对象
        PreparedStatement pstmt=conn.prepareCall(sql);
        //设置？的值
        pstmt.setString(1,name);
        pstmt.setString(2,pws);

//执行sql
        ResultSet rs=pstmt.executeQuery();

        //判断成功与否
        if(rs.next()) 
            System.out.println("登录过程");
        
        else 
            System.out.println("登陆失败");
        
    
    //释放资源