JDBC获取数据库连接的五种方式

首先要导入jar包(必须且重要)

将jar包复制到工程目录之后 右键选择 Add as Library..

方式1:

public class ConnectionTest {
    @Test
    public void test() throws SQLException {
        Driver driver = new com.mysql.cj.jdbc.Driver();
        String url = "jdbc:mysql://localhost:3306/atguigudb";
        Properties info = new Properties();
        info.setProperty("user","root");
        info.setProperty("password","root");
        Connection connection = driver.connect(url, info);
        System.out.println(connection);
    }
}

方式2:在程序中不出现第三方api 使程序具有更好的可移植性

public class ConnectionTest {
    @Test
    public void test() throws Exception {
        //使用反射来获取Driver实现类对象
        Class aClass = Class.forName("com.mysql.cj.jdbc.Driver");
        Driver driver = (Driver) aClass.getDeclaredConstructor().newInstance();
        //提供要连接的数据库
        String url = "jdbc:mysql://localhost:3306/atguigudb";
        //提供要连接数据库的用户名和密码
        Properties info = new Properties();
        info.setProperty("user","root");
        info.setProperty("password","root");
        //获取连接
        Connection connection = driver.connect(url, info);
        System.out.println(connection);
    }
}

方式3:使用DriverManger替换Driver

public class ConnectionTest {
    @Test
    public void test() throws Exception {
        //使用反射来获取Driver实现类对象
        Class aClass = Class.forName("com.mysql.cj.jdbc.Driver");
        Driver driver = (Driver) aClass.getDeclaredConstructor().newInstance();

        //提供另外三个连接的基本信息
        String url = "jdbc:mysql://localhost:3306/atguigudb";
        String user="root";
        String password="root";
        //注册驱动
        DriverManager.registerDriver(driver);
        //获取连接
        DriverManager.getConnection(url,user,password);
        
        //获取连接
        Connection connection = DriverManager.getConnection(url,user,password);
        System.out.println(connection);
    }
}

方式4:可以只是加载驱动 不用显示的注册驱动

public class ConnectionTest {
    @Test
    public void test() throws Exception {
        //加载Driver 因为mysql的driver实现类中 有一段代码块 
       Class.forName("com.mysql.cj.jdbc.Driver");
        //提供另外三个连接的基本信息
        String url = "jdbc:mysql://localhost:3306/atguigudb";
        String user="root";
        String password="root";
        //获取连接
        DriverManager.getConnection(url,user,password);
        //获取连接
        Connection connection = DriverManager.getConnection(url,user,password);
        System.out.println(connection);
    }
}

方式5:将数据库连接需要的4个基本信息生命在配置文件中 通过读取配置文件的方式 获取连接

public class ConnectionTest {
    @Test
    public void test() throws Exception {

        //读取配置文件中的4个基本信息
        InputStream is = ConnectionTest.class.getClassLoader().getResourceAsStream("jdbc.properties");
        Properties pro = new Properties();
        pro.load(is);

        String user = pro.getProperty("user");
        String url = pro.getProperty("url");
        String password = pro.getProperty("password");
        String driverClass = pro.getProperty("driverClass");
        Class.forName("com.mysql.cj.jdbc.Driver");


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

jdbc.properties

url=jdbc:mysql://localhost:3306/atguigudb
user=root
password=root
driverClass=com.mysql.cj.jdbc.Driver