Getting started with JDBC

jdbc introduction

package com.itheima.jdbc;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;

public class JDBC {
    
    public static void main(String[] args) throws Exception {
    
        Class.forName("com.mysql.jdbc.Driver");
        String username="root";
        String url="jdbc:mysql://localhost:3306/db1";
        String password="1234q";
        Connection connection = DriverManager.getConnection(url, username, password);
        String sql="update account set money =2000 where id=1;";
        Statement statement = connection.createStatement();
        int count=statement.executeUpdate(sql);
        System.out.println(count);
        statement.close();
        connection.close();
    }
}

api Detailed explanation

DriverManager

connection Detailed explanation

statement

ResultSet

package com.itheima.jdbc;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class JDBC_ResultSet {
    
    public static void main(String[] args) throws Exception {
    
        Class.forName("com.mysql.jdbc.Driver");
        String username="root";
        //String url="jdbc:mysql://localhost:3306/db1";
        String url="jdbc:mysql:///db1?useSSL=false";
        String password="1234";
        Connection connection = DriverManager.getConnection(url, username, password);
        /*String sql="update account set money =2000 where id=1;"; Statement statement = connection.createStatement(); int count=statement.executeUpdate(sql);*/
       // System.out.println(count);
        String sql="select *from account";
        Statement statement=connection.createStatement();
        ResultSet resultSet = statement.executeQuery(sql);
        while(resultSet.next())
        {
    
            int id=resultSet.getInt("id");
            String name=resultSet.getString("name");
            double money=resultSet.getDouble("money");
            System.out.println(id);
            System.out.println(name);
            System.out.println(money);
            System.out.println("---------------------");
        }

        statement.close();
        connection.close();
        resultSet.close();
    }
}

PreparedStatement

package com.itheima.jdbc;
import jdk.jfr.StackTrace;
import org.testng.annotations.Test;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class userlogin {
    
    @Test
    public void testResultSet() throws Exception
    {
    
      // Class.forName("com.mysql.jdbc.Driver");
        String username="root";
        //String url="jdbc:mysql://localhost:3306/db1";
        String url="jdbc:mysql:///db1?useSSL=false";
        String password="1234";
        Connection connection = DriverManager.getConnection(url, username, password);
        String name="zhangsan";
        String pwd="' or '1'='1";
        String sql="select * from login where username='"+name+"' and userpassword='"+pwd+"'";
        System.out.println(sql);
        Statement statement = connection.createStatement();
        ResultSet rs=statement.executeQuery(sql);
       // System.out.println(count);
        if(rs.next())
        {
    
            System.out.println(" Registered successfully ");
        }else
        {
    
            System.out.println(" Registration failed ");
        }
        statement.close();
        connection.close();
    }
}

package com.itheima.jdbc;

import org.testng.annotations.Test;

import java.sql.*;

public class JDBC_Parparedstatment {
    
    @Test
    public void testResultSet() throws Exception
    {
    
      // Class.forName("com.mysql.jdbc.Driver");
        String username="root";
        //String url="jdbc:mysql://localhost:3306/db1";
        String url="jdbc:mysql:///db1?useSSL=false";
        String password="1234";
        Connection connection = DriverManager.getConnection(url, username, password);
        String name="zhangsan";
        String pwd="123";
        String sql="select * from login where username= ? and userpassword = ?";
        System.out.println(sql);
        //Statement statement = connection.createStatement();
        PreparedStatement preparedStatement = connection.prepareStatement(sql);
        preparedStatement.setString(1,name);
        preparedStatement.setString(2,pwd);
        ResultSet rs=preparedStatement.executeQuery();
       // System.out.println(count);
        if(rs.next())
        {
    
            System.out.println(" Registered successfully ");
        }else
        {
    
            System.out.println(" Registration failed ");
        }
        preparedStatement.close();
        connection.close();
    }
}

preparedStatement principle

Database connection pool

package Druid;

import com.alibaba.druid.pool.DruidDataSource;
import com.alibaba.druid.pool.DruidDataSourceFactory;
import javax.sql.DataSource;
import java.io.FileInputStream;
import java.sql.Connection;
import java.util.Map;
import java.util.Properties;

public class Druiddemo {
    

    public static void main(String[] args) throws Exception {
    
        System.out.println(System.getProperty("user.dir"));
        Properties prop=new Properties();
        prop.load(new FileInputStream("D:/javacode/jdbcMaven/src/druid.properties"));
        DataSource dataSource = DruidDataSourceFactory.createDataSource(prop);
        Connection connection= dataSource.getConnection();
        System.out.println(connection);
    }
}

Case study

package Druid;
import com.alibaba.druid.pool.DruidDataSourceFactory;
import org.junit.Test;

import javax.sql.DataSource;
import java.io.FileInputStream;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

public class BrandTest {
    
    @Test
    public void testSelectAll() throws Exception {
    
        System.out.println(System.getProperty("user.dir"));
        Properties prop=new Properties();
        prop.load(new FileInputStream("D:/javacode/jdbcMaven/src/druid.properties"));
        DataSource dataSource = DruidDataSourceFactory.createDataSource(prop);
        Connection connection= dataSource.getConnection();
        String sql="select * from tb_brand";
        PreparedStatement preparedStatement = connection.prepareStatement(sql);
        ResultSet resultSet = preparedStatement.executeQuery();
        List<Brand>list=new ArrayList<>();
        while(resultSet.next())
        {
    
            Integer id=resultSet.getInt(1);
            String brand_name=resultSet.getString(2);
            String company_name=resultSet.getString(3);
            Integer ordered=resultSet.getInt(4);
            String description=resultSet.getString(5);
            Integer status=resultSet.getInt(6);
            Brand brand=new Brand(id,brand_name,company_name,ordered,description,status);
            list.add(brand);
        }
        for (Brand brand : list) {
    
            System.out.println(brand);
        }
    }
}

-- auto-generated definition
create table tb_brand
(
    id           int auto_increment
        primary key,
    brand_name   varchar(20) charset utf8  null,
    company_name varchar(20) charset utf8  null,
    ordered      int                       null,
    description  varchar(100) charset utf8 null,
    status       int                       null
);