jdbc获取数据库连接方式5种方式

ConnectionTest.java 

package com.demo.connection;
import org.junit.Test;

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

public class ConnectionTest {
    // 方式一
    @Test
    public void testConnection1() throws SQLException {
        Driver driver = new com.mysql.cj.jdbc.Driver();
        String url = "jdbc:mysql://localhost:3306/erp";
        Properties info =  new Properties();
        info.setProperty("user", "root");
        info.setProperty("password", "root");
        Connection conn = driver.connect(url, info);
        System.out.println(conn);
    }

    // 方式二：对方式一的迭代，在如下的程序中不出现第三方的api，使得程序具有更好地移植性
    @Test
    public void testConnection2() throws SQLException, ClassNotFoundException, InstantiationException, IllegalAccessException {
        // 1.获取driver 实现对象：使用反射
        Class clazz = Class.forName("com.mysql.cj.jdbc.Driver");
        Driver driver = (Driver) clazz.newInstance();

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

        // 3.提供要连接的用户名和密码
        Properties info =  new Properties();
        info.setProperty("user", "root");
        info.setProperty("password", "root");

        // 4.获取连接
        Connection conn = driver.connect(url, info);
        System.out.println(conn);
    }

    // 方式三：使用DriverManager替换Driver
    @Test
    public void testConnection3() throws ClassNotFoundException, InstantiationException, IllegalAccessException, SQLException {
        // 注册驱动
        Class clazz = Class.forName("com.mysql.cj.jdbc.Driver");
        Driver driver = (Driver) clazz.newInstance();
        DriverManager.registerDriver(driver);
        // 获取连接
        String url = "jdbc:mysql://localhost:3306/erp";
        String user = "root";
        String password = "root";
        Connection conn = DriverManager.getConnection(url, user, password);
        System.out.println(conn);
    }

    // 方式四：可以只是加载驱动, 对方式三的迭代
    @Test
    public void testConnection4() throws ClassNotFoundException, SQLException {
        // 注册驱动
       Class.forName("com.mysql.cj.jdbc.Driver");
        // 获取连接
        String url = "jdbc:mysql://localhost:3306/erp";
        String user = "root";
        String password = "root";
        Connection conn = DriverManager.getConnection(url, user, password);
        System.out.println(conn);
    }

    // 方式五: 将数据库连接信息放在配置文件中
    @Test
    public void testConnection5() throws IOException, ClassNotFoundException, SQLException {
        // 1.读取配置文件中的配置信息
       InputStream is = ConnectionTest.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 conn = DriverManager.getConnection(url, user, password);
        System.out.println(conn);
    }
}

jdbc.properties

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