JDBC获取数据库连接的5种方式实例

package connection;
 
import java.sql.Connection;
import java.sql.Driver;
import java.sql.SQLException;
import java.util.Properties;
 
import org.junit.jupiter.api.Test;
 
public class ConnectionTest {
    @Test
    public void test() throws SQLException {
        //创建Driver实例
        Driver driver=new com.mysql.cj.jdbc.Driver();
        //获取要读取数据库的URL
        String url="jdbc:mysql://localhost:3306/test04_emp";
        //将账号密码封装到Properties对象中
        Properties info=new Properties();
        info.setProperty("user", "root");
        info.setProperty("password", "abc123");
        //通过Driver的对象获取连接
        Connection connect=driver.connect(url, info);
        //调用连接的toString()
        System.out.println(connect);
    }
}

@Test
    public void test2() throws Exception {
        //通过反射的方式获取运行时类
        Class clazz=Class.forName("com.mysql.cj.jdbc.Driver");
        //通过反射的方式创建运行时类对象
        Driver driver=(Driver)clazz.newInstance();
        //获取URL
        String url="jdbc:mysql://localhost:3306/test04_emp";
        //封装账号密码
        Properties info=new Properties();
        info.setProperty("user", "root");
        info.setProperty("password", "abc123");
        //获取连接
        Connection connect=driver.connect(url, info);
        System.out.println(connect);
    }

@Test
    public void test3() throws Exception {
        //通过反射的方式获取Driver对象
        Driver driver=(Driver)Class.forName("com.mysql.cj.jdbc.Driver").newInstance();
        //调用DriverManager的registerDriver(Driver driver)方法注册驱动
        DriverManager.registerDriver(driver);
        //提供账号、密码和URL
        String user="root";
        String password="abc123";
        String url="jdbc:mysql://localhost:3306/test04_emp";
        //调用DriverManager的getConnection()方法来获取连接
        Connection connect=DriverManager.getConnection(url,user,password);
        System.out.println(connect);
        /*getConnection()还有一种版本：getConnection(String url,Properties info)
         * 可以参考方法一和方法二。
         */
    }

@Test
    public void test4() throws Exception {
        //通过反射将Driver加载到内存中
        Class.forName("com.mysql.cj.jdbc.Driver");
        //提供相关信息
        String user="root";
        String password="abc123";
        String url="jdbc:mysql://localhost:3306/test04_emp";
        //通过getConnection()获取连接
        Connection connect=DriverManager.getConnection(url,user,password);
        System.out.println(connect);
    }

@Test
    public void test5() throws Exception {
        //通过类加载器创建一个指向配置文件的流
        InputStream input=ConnectionTest.class.getClassLoader().getResourceAsStream("test.properties");
        //创建Properties对象
        Properties infoProperties=new Properties();
        //以流为参数调用load()加载配置文件
        infoProperties.load(input);
        //获取相关信息
        String driver=infoProperties.getProperty("driver");
        String url=infoProperties.getProperty("url");
        String user=infoProperties.getProperty("user");
        String password=infoProperties.getProperty("password");
        //加载驱动
        Class.forName(driver);
        //获取连接
        Connection connection= DriverManager.getConnection(url, user, password);
        System.out.println(connection);
    }