获取数据库连接的方式三

https://www.bilibili.com/video/BV1eJ411c7rf?p=9

使用 DriverManager 替换 Driver

import org.junit.Test;

import java.sql.Connection;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.SQLException;

public class ConnectionTest3 {

    @Test
    public void testConnection() throws SQLException, ClassNotFoundException, InstantiationException,
            IllegalAccessException {

        //1.获取 Driver 实现类的对象
        Class<?> clazz = Class.forName("com.mysql.cj.jdbc.Driver");
        Driver driver = (Driver) clazz.newInstance();

        //2.提供另外三个连接的基本信息
        String url = "jdbc:mysql://localhost:3306/guns";
        String user = "root";
        String password = "123456";

        //注册驱动
        DriverManager.registerDriver(driver);

        Connection conn = DriverManager.getConnection(url, user, password);

        System.out.println(conn);

    }

}

com.mysql.cj.jdbc.ConnectionImpl@4278a03f

还有没说的：

DriverManager.registerDriver(driver);

这行代码对于 mysql-connector-java-8.0.30.jar 来说不需要，因为 作为新版本的连接驱动，它的实现在通过反射实例化 Class 对象的时候，已经注册过驱动了，见源码：

package com.mysql.cj.jdbc;

public class Driver extends NonRegisteringDriver implements java.sql.Driver {
    //
    // Register ourselves with the DriverManager
    //
    static {
        try {
            java.sql.DriverManager.registerDriver(new Driver());
        } catch (SQLException E) {
            throw new RuntimeException("Can't register driver!");
        }
    }

    /**
     * Construct a new driver and register it with DriverManager
     * 
     * @throws SQLException
     *             if a database error occurs.
     */
    public Driver() throws SQLException {
        // Required for Class.forName().newInstance()
    }
}