import java.io.FileReader;
import java.io.IOException;
import java.net.URL;
import java.sql.*;
import java.util.Properties;

/**
 * 设计JDBC工具类
 */
public class JDBCUtil {
    private static String driver;
    private static String url;
    private static String user;
    private static String pwd;

    /**
     * 只需要读取一次读取配置文件jdbc.properties
     */
    static {
        try {
            //1.创建Properties集合类
            Properties prop = new Properties();
            //获取src路径下的文件的方式：ClassLoader类加载器
            ClassLoader loader = JDBCUtil.class.getClassLoader();
            URL propUrl = loader.getResource("jdbc.properties");
            String path = propUrl.getPath();
            System.out.println(path);
            //2.加载文件
            prop.load(new FileReader(path));
            //3.获取值
            driver = prop.getProperty("driver");
            url = prop.getProperty("url");
            user = prop.getProperty("user");
            pwd = prop.getProperty("pwd");
            //4.注册驱动
            Class.forName(driver);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }


    /**
     * 获取连接
     *
     * @return 连接对象
     */
    public static Connection getConnection() {
        try {
            return DriverManager.getConnection(url, user, pwd);
        } catch (SQLException e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 释放资源
     *
     * @param stmt Statement对象
     * @param conn Connection对象
     */
    public static void close(Statement stmt, Connection conn) {
        close(null, stmt, conn);
    }

    /**
     * 释放资源
     *
     * @param rs   ResultSet对象
     * @param rs   ResultSet对象
     * @param stmt Statement对象
     * @param conn Connection对象
     */
    public static void close(ResultSet rs, Statement stmt, Connection conn) {
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (stmt != null) {
            try {
                stmt.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/数据库名称
user=用户名
pwd=密码

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.sql.*;
import java.util.Properties;

/**
 * 设计Druid连接池工具类
 */
public class DruidUtil {
    //定义成员变量DataSource
    private static DataSource ds;

    /**
     * 对DataSource初始化赋值
     */
    static {
        try {
            //1.加载配置文件
            Properties prop = new Properties();
            InputStream is = DruidUtil.class.getClassLoader().getResourceAsStream("druid.properties");
            prop.load(is);
            //2.赋值
            ds = DruidDataSourceFactory.createDataSource(prop);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }


    /**
     * 获取连接
     *
     * @return 连接对象
     */
    public static Connection getConnection() {
        try {
            return ds.getConnection();
        } catch (SQLException e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 释放资源
     *
     * @param stmt Statement对象
     * @param conn Connection对象
     */
    public static void close(Statement stmt, Connection conn) {
        close(null, stmt, conn);
    }

    /**
     * 释放资源
     *
     * @param rs   ResultSet对象
     * @param rs   ResultSet对象
     * @param stmt Statement对象
     * @param conn Connection对象
     */
    public static void close(ResultSet rs, Statement stmt, Connection conn) {
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (stmt != null) {
            try {
                stmt.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (conn != null) {
            try {
                conn.close();//归还连接
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/数据库名称
username=用户名
password=密码
initialSize=5
maxActive=10
maxWait=3000