使用：props.load(DBUtils.class.getClassLoader().getResourceAsStream("day01/db.properties"));

导入配置文件

使用的是反射机制

.class   ///获得Class对象

.class.getClassLoader()   ///获得ClassLoader对象

.class.getClassLoader().getResourceAsStream(String name);  //获得inputStream对象

所以括号里是inputStream对象  这肯定是不变的

///DBUtils.java

package day02;

import java.io.File;

import java.io.FileInputStream;

import java.sql.Connection;

import java.sql.DriverManager;

import java.util.Properties;

public class DBUtils {

private static String driver;

private static String url;

private static String user;

private static String password;

static{

try{

Properties props = new Properties();

//从类路径中加载文件

props.load(DBUtils.class.getClassLoader().getResourceAsStream("day01/db.properties"));

//props.load(new FileInputStream("db.properties"));

driver = props.getProperty("driver");

url = props.getProperty("url");

user = props.getProperty("user");

password = props.getProperty("password");

System.out.println(driver);

System.out.println(url);

System.out.println(user);

Class.forName(driver);

}catch(Exception e){

throw new RuntimeException(e);

}

}

public static Connection openConnection() throws Exception{         //静态方法获得连接

Connection con = DriverManager.getConnection(url,user,password);

return con;

}

}