Java连接MySQL数据库的五种方式，jdbc

package day38;
 
import com.mysql.jdbc.Driver;
import org.junit.jupiter.api.Test;
 
import java.io.FileInputStream;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;
 
/**
 * @Author:monian
 * @Wo yi wu ta,wei shou shu er!
 * @Date:2023/11/14 12:09
 */
public class JdbcConn {
    @SuppressWarnings({"all"})
    @Test
    public void connect01() throws SQLException {
        // 方式1
        Driver driver = new Driver();
        String url = "jdbc:mysql://localhost:3306/mn_db02";
        // 将用户名和密码放入到Properties对象
        Properties properties = new Properties();
        properties.setProperty("user", "root");
        properties.setProperty("password", "chen");
        Connection connect = driver.connect(url, properties);
        System.out.println("方式1" + connect);
    }
 
    @Test
    //方式2
    public void connect02() throws InstantiationException, IllegalAccessException, ClassNotFoundException, SQLException {
        //使用反射加载Driver类
        Class<?> aClass = Class.forName("com.mysql.jdbc.Driver");
        Driver driver = (Driver) aClass.newInstance();
 
        String url = "jdbc:mysql://localhost:3306/mn_db02";
        // 将用户名和密码放入到Properties对象
        Properties properties = new Properties();
        properties.setProperty("user", "root");
        properties.setProperty("password", "chen");
 
        Connection connect = driver.connect(url, properties);
        System.out.println("方式2=" + connect);
    }
 
    @Test
    //方式3 使用DriverManager 替代 Driver 进行统一管理
    public void connect03() throws ClassNotFoundException, InstantiationException, IllegalAccessException, SQLException {
        Class<?> aClass = Class.forName("com.mysql.jdbc.Driver");
        Driver driver = (Driver) aClass.newInstance();
 
        //创建url 和 user 和 password
        String url = "jdbc:mysql://localhost:3306/mn_db02";
        String user = "root";
        String password = "chen";
 
        DriverManager.registerDriver(driver);
 
        Connection connection = DriverManager.getConnection(url, user, password);
        System.out.println("方式3=" + connection);
    }
 
    @Test
    /**方式4： 使用Class.forName 自动完成注册驱动，简化代码
     * 推荐指数：*****
     */
    public void connect04() throws ClassNotFoundException, SQLException {
        //使用反射加载了Driver
        //再加载Driver类时，完成注册
/*
        源码：1.静态代码块，在类加载一次，会执行一次
             2.DriverManager.registerDriver(new Driver());
             3.因此注册driver的工作已经完成
         static {
            try {
                DriverManager.registerDriver(new Driver());
            } catch (SQLException var1) {
                throw new RuntimeException("Can't register driver!");
            }
       }
  */
 
        Class.forName("com.mysql.jdbc.Driver"); // 删除也可以。建议写上
        //创建url 和 user 和 password
        String url = "jdbc:mysql://localhost:3306/mn_db02";
        String user = "root";
        String password = "chen";
        Connection connection = DriverManager.getConnection(url, user, password);
 
        System.out.println("方式4~" + connection);
    }
 
    @Test
    //推荐指数：****** 代码简洁+反射机制
    //方式5 ,在方式4的基础上改进，增加配置文件，让连接mysql更加灵活
    public void connect05() throws IOException, ClassNotFoundException, SQLException {
 
        //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"));
        String user = properties.getProperty("user");
        String password = properties.getProperty("password");
        String url = properties.getProperty("url");
        String driver = properties.getProperty("driver");
 
        Class.forName(driver);//建议写上
 
        Connection connection = DriverManager.getConnection(url, user, password);
 
        System.out.println("方式5=" + connection);
    }
}