JDBC 2—— 获取数据库连接

 JDBCTest01.class

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

import com.mysql.jdbc.Driver;

public class JDBCTest01 {
    public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException, SQLException, IOException {
        testConnection5();
    }

    //方式一：
    public static void testConnection1() throws SQLException {
        // 1、注册驱动
        Driver driver = new com.mysql.jdbc.Driver();
        // url:http//localhost:8080/gmall/keyboard.jpg
        // jdbc:mysql:协议
        // 3360:默认mysql的端口号
        // test:test数据库
        String url = "jdbc:mysql://localhost:3306/MySQL";
        Properties info = new Properties();
        // 将用户名和密码封装在Propect中
        info.setProperty("user", "root");
        info.setProperty("password", "root");
        Connection coon = driver.connect(url, info);
        System.out.println(coon);
    }
    
    //方式二：对方式一的迭代
    public static void testConnection2() throws ClassNotFoundException, InstantiationException, IllegalAccessException, SQLException{
        //1、获取Driver实现类对象，使用反射
        Class<?> clazz = Class.forName("com.mysql.jdbc.Driver");
        @SuppressWarnings("deprecation")
        Driver driver = (Driver) clazz.newInstance();
        
        //2、提供要连接的数据库
        String url = "jdbc:mysql://localhost:3306/MySQL";
        
        //3、提供连接需要的用户名和密码
        Properties info = new Properties();
        info.setProperty("user", "root");
        info.setProperty("password", "root");
        
        //4、获取连接
        Connection coon = driver.connect(url, info);
        System.out.println(coon);
    }
    
    //方式三：使用DriverManger替换Driver
    public void testConnection3() throws ClassNotFoundException, InstantiationException, IllegalAccessException {
        //1、获取Driver实现类对象，使用反射
        Class<?> clazz = Class.forName("com.mysql.jdbc.Driver");
        @SuppressWarnings("deprecation")
        Driver driver = (Driver) clazz.newInstance();
        
        //2、提供要连接的数据库
        String url = "jdbc:mysql://localhost:3306/MySQL";
        String user = "root";
        String password = "root";
        
        //3、注册驱动
        DriverManger.registerDriver(driver);
        
        //4、获取连接
        Connection coon = DriverManager.getConnection(url, user, password);
        System.out.println(coon);
    }
    
    //方式四：优化三
    public static void testConnection4() throws ClassNotFoundException, InstantiationException, IllegalAccessException, SQLException {
        //1、提供要连接的数据库
        String url = "jdbc:mysql://localhost:3306/MySQL";
        String user = "root";
        String password = "root";
        
        //2、加载Driver
        Class.forName("com.mysql.jdbc.Driver");
        @SuppressWarnings("deprecation")
//        Driver driver = (Driver) clazz.newInstance();
//        //注册驱动
//        DriverManger.registerDriver(driver);
        //为什么可以省略上述操作呢：
        /*
         * 在mysql的Driver实现类中，申明的如下操作：
         *     static{
         *         try{
         *             java.sql.DriverManager.registerDriver(new Driver());
         *         }catch (SQLException E) {
         *             throw new RuntimeException("Can't register driver!");
         *         }
         *     }
         * */
        
        //3、获取连接
        Connection coon = DriverManager.getConnection(url, user, password);
        System.out.println(coon);
    }
    
    //方式五(final版)：将数据库连接需要的4个基本信息声明在配置文件中，通过读取配置文件的方式，获取连接
    /*
     * 此种方式的好处？
     * 1、实现了数据与代码的分离，实现了解耦
     * 2、如果需要修改配置文件信息，可以避免程序重新打包
     * */
    public static void testConnection5() throws IOException, ClassNotFoundException, SQLException {
        //1、读取配置文件中的4个基本信息
        InputStream is = JDBCTest01.class.getClassLoader().getResourceAsStream("jdbc.properties");
        Properties pros = new Properties();
        pros.load(is);
        
        String user = pros.getProperty("user");
        String password = pros.getProperty("password");
        String url = pros.getProperty("url");
        String driverClass = pros.getProperty("driverClass");
        
        //2、加载驱动
        Class.forName(driverClass);
        
        //3、获取连接
        Connection coon = DriverManager.getConnection(url, user, password);
        System.out.println(coon);
    }
}

jdbc.properties

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