JDBC连接数据库的5种方式

五种方式依次逐渐优化，若无时间，直接记住最后一种即可

public class ConnectionTest {
    @Test
    public void Test1() throws SQLException {
        Driver driver = new com.mysql.jdbc.Driver();
        String url = "jdbc:mysql://localhost:3306/test";    //要连接的数据库test
        //用户名密码在propertieszhogn
        Properties info = new Properties();
        info.setProperty("root", "root");
        Connection connection = driver.connect(url,info);
        System.out.println(connection);
    }
    @Test
    public void test2() throws Exception {
        //test1的迭代版，程序中没有第三方API 提高可移植性；
        //1 反射获取Driver的实现类对象==换数据库方便
        String DriverType = "com.mysql.jdbc.Driver";
        Class clazz = Class.forName(DriverType);
        Driver driver = (Driver) clazz.newInstance();

        //2 提供要连接的数据库
        String url = "jdbc:mysql://localhost:3306/test";    //要连接的数据库test

        //3 提供用户名密码
        Properties info = new Properties();
        info.setProperty("root", "root");

        //4 开始连接
        Connection connection = driver.connect(url,info);
        System.out.println(connection);
    }

    @Test
    public  void test3() throws Exception {
        //DriverManager 替换
        //1 获取Driver实现类对象
        Class clazz = Class.forName("com.mysql.jdbc.Driver");
        Driver driver = (Driver) clazz.newInstance();

        //提供信息
        String url = "jdbc:mysql://localhost:3306/test";    //要连接的数据库test
        String uname="root";
        String pwd="root";


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

        //获取链接
        Connection connection = DriverManager.getConnection(url,uname,pwd);
        System.out.println(connection);

    }

    @Test
    public  void test4() throws Exception {
        //只加载驱动，不用注册
        //提供信息
        String url = "jdbc:mysql://localhost:3306/test";    //要连接的数据库test
        String uname="root";
        String pwd="root";


        //获取Driver实现类对象//mysql.Driver自带的静态代码执行了对象创建
          Class.forName("com.mysql.jdbc.Driver");


        //获取链接
        Connection connection = DriverManager.getConnection(url,uname,pwd);
        System.out.println(connection);

    }
  @Test//通过配置文件加载
        public void finalConn() throws Exception {
      InputStream is = ConnectionTest.class.getClassLoader().getResourceAsStream("jdbc.properties");
      Properties pros = new Properties();
      pros.load(is);
      String username = pros.getProperty("username");
      String password = pros.getProperty("password");
      String url = pros.getProperty("url");
      String classDriver = pros.getProperty("driverClass");

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


jdbc.properties 的内容为：
username=root
password=root
url=jdbc:mysql://localhost:3306/test
driverClass=com.mysql.jdbc.Driver
建议将其创建在src目录下