数据库连接方式

方式一

直接使用com.mysql.jdbc.Driver(),属于静态加载，灵活性差，依赖性强 推出方式2

public void connect01() throws SQLException {
          
   
      //创建dirver对象
       Driver driver =new Driver();

       String  url = "jdbc:mysql://localhost:3306/studb";
       //用户名与密码放入properties对象
       Properties properties = new Properties();
       properties.setProperty("user","root");
       properties.setProperty("password","123456");
       //建立连接
       Connection connection = driver.connect(url,properties);
       System.out.println(connection);
   }

方式二

利用反射加载Driver类，动态加载，更加灵活

public void connect02() throws ClassNotFoundException, InstantiationException, IllegalAccessException, SQLException {
          
   
        Class<?> aClass = Class.forName("com.mysql.cj.jdbc.Driver");
        Driver driver = (Driver) aClass.newInstance();

        String  url = "jdbc:mysql://localhost:3306/studb";
        //用户名与密码放入properties对象
        Properties properties = new Properties();
        properties.setProperty("user","root");
        properties.setProperty("password","123456");
        //建立连接
        Connection connection = driver.connect(url,properties);
        System.out.println(connection);

    }

方式三

用DriverManager替代Driver进行统一管理,具有更好的扩展性

public void connect03() throws ClassNotFoundException, InstantiationException, IllegalAccessException, SQLException {
          
   
        //利用反射加载Driver
        Class<?> aClass = Class.forName("com.mysql.cj.jdbc.Driver");
        Driver driver = (Driver) aClass.newInstance();
        //创建url和user和password
        String  url = "jdbc:mysql://localhost:3306/studb";
        String user = "root";
        String password = "123456";
//      注册Driver驱动
        DriverManager.registerDriver(driver);
        Connection connection = DriverManager.getConnection(url, user, password);
        System.out.println(connection);
    }

方式四

使用Class.forName 自动完成注册驱动，简化代码 是使用最多的

public void connect04() throws ClassNotFoundException, SQLException {
          
   
        //利用反射加载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));
        static {
        try {
            DriverManager.registerDriver(new Driver());
        } catch (SQLException var1) {
            throw new RuntimeException("Cant register driver!");
        }
    }
}
         */
        Class.forName("com.mysql.cj.jdbc.Driver");

        //创建url，user，password
        String  url = "jdbc:mysql://localhost:3306/studb";
        String user = "root";
        String password = "123456";
        Connection connection = DriverManager.getConnection(url,user,password);

        System.out.println(connection);
    }

方式五

实际开发中比较好的，在方式4上改进，使用配置文件，连接数据库更加灵活

public void connect05() throws IOException, ClassNotFoundException, SQLException {
          
   
        //通过properties对象获取文件信息
        Properties properties = new Properties();
        properties.load(new FileInputStream("src\Jdbc\myjdbc\mysql.properities"));
        //获取相关的值
        String user = properties.getProperty("user");
        String url = properties.getProperty("url");
        String driver = properties.getProperty("driver");
        String password = properties.getProperty("password");

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