JDBC

https://www.bilibili.com/video/BV1NJ411J79W?p=40&spm_id_from=333.880.my_history.page.click
口诀:贾琏欲执事(加连预执释) 引入依赖,加载驱动 连接数据库 创建预编译语句 设置参数,执行sql 关闭连接,释放资源

package com.kuang.lesson01;

import java.sql.*;

public class JdbcFirstDemo {
    public static void main(String[] args) throws ClassNotFoundException, SQLException {
        // 加载驱动
        Class.forName("com.mysql.jdbc.Driver");

        // 用户信息和URL
        String url= "jdbc:mysql://localhost:3306/jdbcstudy?useUnicode=true&characterEncoding=utf8&useSSL=false";
        String username="root";
        String password = "123456";

        // 连接成功，数据库对象 connection 代表数据库
        Connection connection = DriverManager.getConnection(url, username, password);
        // 执行SQL对象 statement 执行sql 语句
        Statement statement = connection.createStatement();
        //执行sql的对象去执行 sql , 可能存在结果，查看返回结果
        String sql= "select * from users";
        ResultSet resultSet = statement.executeQuery(sql);
        while (resultSet.next()){
            System.out.println("id="+resultSet.getObject("id"));
            System.out.println("username="+resultSet.getObject("NAME"));
            System.out.println("password="+resultSet.getObject("PASSWORD"));
            System.out.println("email="+resultSet.getObject("email"));
            System.out.println("birth="+resultSet.getObject("birthday"));
            System.out.println("=====================================================");
        }

        // 释放连接
        resultSet.close();
        statement.close();
        connection.close();


    }
    
}

增

package com.kuang.lesson02;

import com.kuang.lesson02.utils.JdbcUtils;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class TestInsert {
    public static void main(String[] args) throws SQLException {
        Connection conn =null;
        Statement st=null;
        ResultSet rs=null;
        try {
            conn = JdbcUtils.getConnection(); // 获取数据库连接
            st=conn.createStatement();       // 获得sql的执行对象
            String sql="INSERT INTO users(`id`, `NAME`,`PASSWORD`,`email`,`birthday`)" +
                    "VALUES(4,'kuangshen','123456','1234@qq.com','2020-01-01')";
            int i = st.executeUpdate(sql);
            if(i>0){
                System.out.println("插入成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.release(conn,st,rs);
        }
    }
}

删

package com.kuang.lesson02;

import com.kuang.lesson02.utils.JdbcUtils;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class TestDelete {
    public static void main(String[] args) {
        Connection conn =null;
        Statement st=null;
        ResultSet rs=null;
        try {
            conn = JdbcUtils.getConnection(); // 获取数据库连接
            st=conn.createStatement();       // 获得sql的执行对象
            String sql="DELETE from users WHERE id=4;";
            int i = st.executeUpdate(sql);
            if(i>0){
                System.out.println("删除成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.release(conn,st,rs);
        }
    }

}

改

package com.kuang.lesson02;

import com.kuang.lesson02.utils.JdbcUtils;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class TestUpdate {
    public static void main(String[] args) {
        Connection conn =null;
        Statement st=null;
        ResultSet rs=null;
        try {
            conn = JdbcUtils.getConnection(); // 获取数据库连接
            st=conn.createStatement();       // 获得sql的执行对象
            String sql="UPDATE  users set NAME='kuangsheng', email='1234567@qq.com' where id=1;";
            int i = st.executeUpdate(sql);
            if(i>0){
                System.out.println("更新成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.release(conn,st,rs);
        }
    }
}

查询（代码比较特殊）

package com.kuang.lesson02;

import com.kuang.lesson02.utils.JdbcUtils;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class TestSelect {
    public static void main(String[] args) {
        Connection conn=null;
        Statement st=null;
        ResultSet rs=null;

        try {
            conn = JdbcUtils.getConnection();
            st= conn.createStatement();

            // SQL
            String sql="select * from users where id=1";
             rs= st.executeQuery(sql);
             if(rs.next()){
                 System.out.println(rs.getObject("NAME"));
             }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        finally {
            JdbcUtils.release(conn,st,rs);
        }
    }
}