jdbc的几种连接方式

1、获取Driver实现类对象

public void conn1() throws SQLException {
        //注册驱动
        Driver driver = new Driver();

        //获取连接
        String url = "jdbc:mysql://127.0.0.1:3306/jdbc?useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC";
        Properties properties = new Properties();
        properties.setProperty("user", "root");
        properties.setProperty("password", "1234");

        Connection connection = driver.connect(url, properties);
        System.out.println(connection);
    }

2、利用反射机制

public void conn2() throws ClassNotFoundException, IllegalAccessException, InstantiationException, SQLException {
        Class<?> aClass = Class.forName("com.mysql.jdbc.Driver");
        Driver driver = (Driver)aClass.newInstance();

        String url = "jdbc:mysql://127.0.0.1:3306/jdbc?useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC";
        Properties properties = new Properties();
        properties.setProperty("user", "root");
        properties.setProperty("password", "1234");

        Connection connection = driver.connect(url, properties);
        System.out.println(connection);
    }

3、使用DriverManager替换Driver

public void conn3() throws ClassNotFoundException, IllegalAccessException, InstantiationException, SQLException {
        Class<?> aClass = Class.forName("com.mysql.jdbc.Driver");
        Driver driver = (Driver)aClass.newInstance();

        String url = "jdbc:mysql://127.0.0.1:3306/jdbc?useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC";
        String user = "root";
        String password = "1234";

        DriverManager.registerDriver(driver);
        Connection connection = DriverManager.getConnection(url, user, password);
        System.out.println(connection);
    }

4、使用Class.forName()自动完成注册驱动

public void conn4() throws ClassNotFoundException, SQLException {
        //Class.forName()自动完成注册驱动
        Class.forName("com.mysql.jdbc.Driver");

        String url = "jdbc:mysql://127.0.0.1:3306/jdbc?useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC";
        String user = "root";
        String password = "1234";

        Connection connection = DriverManager.getConnection(url, user, password);
        System.out.println(connection);
    }

Driver源码

public class Driver extends NonRegisteringDriver implements java.sql.Driver {
    public Driver() throws SQLException {
    }

    static {
        try {
            DriverManager.registerDriver(new Driver());
        } catch (SQLException var1) {
            throw new RuntimeException("Can't register driver!");
        }
    }
}

5、使用配置文件，连接数据库更加灵活

jdbc.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/jdbc?useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=GMT
jdbc.username=root
jdbc.password=1234

public void conn5() throws ClassNotFoundException, IOException, SQLException {
        Properties properties = new Properties();
        properties.load(new FileInputStream(new File("src\\jdbc.properties")));

        String user = properties.getProperty("jdbc.username");
        String password = properties.getProperty("jdbc.password");
        String driver = properties.getProperty("jdbc.driver");
        String url = properties.getProperty("jdbc.url");

        Class.forName(driver);

        Connection connection = DriverManager.getConnection(url, user, password);
        System.out.println(connection);
    }