JavaWeb-JDBC-API详解

一、JDBC介绍

二、JDBC 快速入门

package com.itheima.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;

public class JDCBDemo {
    public static void main(String[] args) throws Exception {
        //1、注册驱动
        Class.forName("com.msql.jdbc.Driver");

        //2、获取链接
        String url = "jdbc:mysql://127.0.0.1:3306/db1";
        String username = "root";
        String password = "123456";
        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、释放资源
        stmt.close();
        conn.close();
    }
}

三、JDBC API详解

1、DriverManager

2、Connection

//3、定义sql
        String sql1 = "update account set money = 3000 where id = 1";
        String sql2 = "update account set money = 3000 where id = 2";
        Statement stmt = conn.createStatement();

        try {
            //开启事物
            conn.setAutoCommit(false);

            int count1 = stmt.executeUpdate(sql1);
            System.out.println(count1);
            int count2 = stmt.executeUpdate(sql2);
            System.out.println(count2);

            //提交事物
            conn.commit();
        } catch (Exception throwables) {
            //回滚事物
            conn.rollback();
            throwables.printStackTrace();
        }

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

3、Statement

package com.itheima.jdbc;

import java.sql.*;

public class JDCBDemo {
    public static void main(String[] args) throws Exception {
        //1、注册驱动
        Class.forName("com.msql.jdbc.Driver");

        //2、获取链接
        String url = "jdbc:mysql://127.0.0.1:3306/db1";
        String username = "root";
        String password = "123456";
        Connection conn = DriverManager.getConnection(url, username, password);

        //3、定义sql
        String sql = "select * from account";

        //4、获取statememt对象
        Statement stmt = conn.createStatement();

        //5、执行sql
        ResultSet rs = stmt.executeQuery(sql);

        //6、处理结果，遍历rs中的所有数据
        //6.1 光标向下移动一行，并且判断当前是否有数据
        while (rs.next()){
            //6.2 获取数据 getXxx
            int id = rs.getInt(1);
            String name = rs.getString(2);
            double money = rs.getDouble(3);

            System.out.println(id);
            System.out.println(name);
            System.out.println(money);

            System.out.println("----------------------");
        }

        //7、释放资源
        rs.close();
        stmt.close();
        conn.close();
    }
}

4、PrepareStatement

package com.itheima.jdbc;

import java.sql.*;

public class JDCBDemo {
    public static void main(String[] args) throws Exception {
        //1、注册驱动
        Class.forName("com.msql.jdbc.Driver");

        //2、获取链接
        String url = "jdbc:mysql://127.0.0.1:3306/db1";
        String username = "root";
        String password = "123456";
        Connection conn = DriverManager.getConnection(url, username, password);

        //接受用户输入 用户名和密码
        String name = "zhangsan";
        String pwd = "123";
        String sql = "select * from tb_user where username = '" + name + "' and password = '" + pwd + "'";

        //获取stmt对象
        Statement stmt = conn.createStatement();

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

        //判断是否登录成功
        if (rs.next()){
            System.out.println("登录成功");
        }else {
            System.out.println("登录失败");
        }

        //释放资源
        rs.close();
        stmt.close();
        conn.close();
    }
}

package com.itheima.jdbc;

import java.sql.*;

public class JDCBDemo {
    public static void main(String[] args) throws Exception {
        //1、注册驱动
        Class.forName("com.msql.jdbc.Driver");

        //2、获取链接
        String url = "jdbc:mysql://127.0.0.1:3306/db1";
        String username = "root";
        String password = "123456";
        Connection conn = DriverManager.getConnection(url, username, password);

        //接受用户输入 用户名和密码
        String name = "zhangsan";
        String pwd = "123";

        //定义sql
        String sql = "select * from tb_user where username = ? and password = ?";

        //获取pstmt对象
        PreparedStatement pstmt = conn.prepareStatement(sql);

        //设置 ？ 的值
        pstmt.setString(1,name);
        pstmt.setString(2,pwd);

        //执行sql
        ResultSet rs = pstmt.executeQuery();
        
        //判断是否登录成功
        if (rs.next()){
            System.out.println("登录成功");
        }else {
            System.out.println("登录失败");
        }

       //释放资源
        rs.close();
        pstmt.close();
        conn.close();
    }
}