连接数据库的方式

1. 下载 mysql 驱动 jar 包
2. 添加入JAVA程序文件中
3. 添加到 library 库中

package com.ftn.jdbc.myjdbc;

//数据库的不同连接方式
import com.mysql.cj.jdbc.Driver;
import org.junit.jupiter.api.Test;

import java.io.FileInputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

public class JdbcConn {
    public static void main(String[] args) {
    }

    //方式一
    //直接加载Driver对象，获取连接
    @Test
    public void connect01() throws SQLException {
        Driver driver = new Driver();
        Properties properties = new Properties();
        properties.setProperty("user","root");
        properties.setProperty("password","122800");
        Connection connect = driver.connect("jdbc:mysql://localhost:3306/db_03", properties);
        System.out.println("第三种连接方式：" + connect);
        connect.close();
    }

    //方式二
    //使用反射加载 Driver 类，动态加载，更加灵活，减少依赖性
    @Test
    public void connect02() throws Exception {
        Class aClass = Class.forName("com.mysql.cj.jdbc.Driver");
        Driver driver =(Driver) aClass.newInstance();

        //创建 url，user和 password
        Properties properties = new Properties();
        properties.setProperty("user","root");
        properties.setProperty("password","122800");
        Connection connect = driver.connect("jdbc:mysql://localhost:3306/db_03", properties);
        System.out.println("第三种连接方式：" + connect);
        connect.close();
    }

    //方式三
    //使用DriverManager代替Driver进行统一管理
    @Test
    public void connect03() throws Exception {
        //使用反射加载 Driver
        Class aClass = Class.forName("com.mysql.cj.jdbc.Driver");
        Driver driver = (Driver) aClass.newInstance();

        //创建 url，user和 password
        String url = "jdbc:mysql://localhost:3306/db_03";
        String user = "root";
        String password = "122800";

        DriverManager.registerDriver(driver);   //注册 Driver 驱动
        Connection connection = DriverManager.getConnection(url, user, password);
        System.out.println("第三种连接方式：" + connection);
        connection.close();
    }

    //方式四
    //使用 Class.forName 自动完成注册驱动，简化代码
    
    @Test
    public void connect04() throws Exception {
        //使用反射加载 Driver
        

        Class aClass = Class.forName("com.mysql.cj.jdbc.Driver");
        //创建 url，user和 password
        String url = "jdbc:mysql://localhost:3306/db_03";
        String user = "root";
        String password = "122800";

        Connection connection = DriverManager.getConnection(url, user, password);
        System.out.println("第四种方式：" + connection);
        connection.close();
    }

    //方式五
    //在方式四基础上改进，增加配置文件，让连接 mysql 更加灵活
    @Test
    public void connect05() throws Exception {
        //通过 Properties 对象获取配置文件的信息
        Properties properties = new Properties();
        properties.load(new FileInputStream("src\mysql.properties"));

        //获取相关的值
        String url = properties.getProperty("url");
        String user = properties.getProperty("user");
        String password = properties.getProperty("password");
        String driver = properties.getProperty("driver");

        Class aClass = Class.forName(driver);

        Connection connection = DriverManager.getConnection(url, user, password);
        System.out.println("第五种方式：" + connection);
        connection.close();
    }
}