JDBC

package com.hspedu.jdbc;
import com.mysql.jdbc.Driver;
import org.junit.jupiter.api.Test;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;
/**
 * @author 韩顺平
 * @version 1.0
 * 分析java 连接mysql的5中方式
 */
public class JdbcConn {
    //方式1
    @Test
    public void connect01() throws SQLException {
        Driver driver = new Driver(); //创建driver对象
        String url = "jdbc:mysql://localhost:3306/hsp_db02";
        //将 用户名和密码放入到Properties 对象
        Properties properties = new Properties();
        //说明 user 和 password 是规定好，后面的值根据实际情况写
        properties.setProperty("user", "root");// 用户
        properties.setProperty("password", "hsp"); //密码
        Connection connect = driver.connect(url, properties);
        System.out.println(connect);
    }
    //方式2
    @Test
    public void connect02() throws ClassNotFoundException,
    IllegalAccessException, InstantiationException, SQLException {
        //使用反射加载Driver类 , 动态加载，更加的灵活，减少依赖性
        Class<?> aClass = Class.forName("com.mysql.jdbc.Driver");
        Driver driver = (Driver)aClass.newInstance();
        String url = "jdbc:mysql://localhost:3306/hsp_db02";
        //将 用户名和密码放入到Properties 对象
        Properties properties = new Properties();
        //说明 user 和 password 是规定好，后面的值根据实际情况写
        properties.setProperty("user", "root");// 用户
        properties.setProperty("password", "hsp"); //密码
        Connection connect = driver.connect(url, properties);
        System.out.println("方式2=" + connect);
    }
    //方式3 使用DriverManager 替代 driver 进行统一管理
    @Test
    public void connect03() throws IllegalAccessException,
    InstantiationException, ClassNotFoundException, SQLException {
        //使用反射加载Driver
        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/hsp_db02";
        String user = "root";
        String password = "hsp";
        DriverManager.registerDriver(driver);//注册Driver驱动
        Connection connection = DriverManager.getConnection(url, user, password);
        System.out.println("第三种方式=" + connection);
    }
    //方式4: 使用Class.forName 自动完成注册驱动，简化代码
    //这种方式获取连接是使用的最多，推荐使用
    @Test
    public void connect04() throws ClassNotFoundException, SQLException {
        //使用反射加载了 Driver类
        //在加载 Driver类时，完成注册
        /*
            源码: 1. 静态代码块，在类加载时，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");
        //创建url 和 user 和 password
        String url = "jdbc:mysql://localhost:3306/hsp_db02";
        String user = "root";
        String password = "hsp";
        Connection connection = DriverManager.getConnection(url, user, password);
        System.out.println("第4种方式~ " + connection);
    }
    //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
    @Test
    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"));
        //获取相关的值
        String user = properties.getProperty("user");
        String password = properties.getProperty("password");
        String driver = properties.getProperty("driver");
        String url = properties.getProperty("url");
        Class.forName(driver);//建议写上
        Connection connection = DriverManager.getConnection(url, user, password);
        System.out.println("方式5 " + connection);
    }
}