JDBCUtilConfig 读取配置文件的工具类

database.properties:
driverClass=com.mysql.jdbc.Driver
url=jdbc:mysql://192.168.8.14:3306/day22_JDBC
username=root
password=123456

package Day29_JDBC.JDBC_Util;

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

/**
 * @Author quzheng
 * @Date 2019/10/3 12:45
 * @Version 1.0
 * 数据库连接工具类
 * 读取文件获取链接，执行一次，static{}
 */
public class JDBCUtilConfig {
    private static Connection con;
    private static String driverClass;
    private static String url;
    private static String username;
    private static String password;


    static{
        try{
            readConfig();
            Class.forName(driverClass);

            //找了半天，原来是这里重复定义了局部变量Connection con
            //导致返回值仍然是域静态变量con = null
            // Connection con = DriverManager.getConnection(url,username,password);
            con = DriverManager.getConnection(url,username,password);

        } catch (Exception ex){
            throw new RuntimeException(ex+"数据库连接失败");
        }

    }

    private static void readConfig() throws Exception{
        InputStream in = JDBCUtilConfig.class.getClassLoader().getResourceAsStream("database.properties");
        Properties pro = new Properties();
        pro.load(in);
        driverClass = pro.getProperty("driverClass");
        url = pro.getProperty("url");
        username = pro.getProperty("username");
        password = pro.getProperty("password");
    }
    public static Connection getConnection(){
        return con;
    }

}