JDBCUtils

• jdbc.properties配置文件

url=jdbc:mysql://localhost:3306/mydb
user=root
password=ss
driver=com.mysql.jdbc.Driver

• JDBCUtils类

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

/**
 * @author :yangzhipeng
 * @date : 2023/3/9 9:36
 * Description : JDBC工具类
 */

public class JDBCUtils {
    private static String url;
    private static String user;
    private static String password;
    private static String driver;

    //使用配置文件配置连接信息
    //读取文件,只需要读取一次，使用静态代码块
    static {
        //1.创建Properties集合类
        Properties pro = new Properties();
        //2.加载文件
        try {
            //获取当前文件的路径 --->ClassLoader类加载器
            ClassLoader classLoader = JDBCUtils.class.getClassLoader();
            URL res = classLoader.getResource("jdbc.properties");
            // getResource 文件路径中存在中文字符，先解码
            String path = java.net.URLDecoder.decode(res.getPath(),"utf-8");
            pro.load(new FileReader(path));
            //3.获取数据，赋值
            url = pro.getProperty("url");
            user = pro.getProperty("user");
            password = pro.getProperty("password");
            driver = pro.getProperty("driver");
            //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() throws SQLException {

        return DriverManager.getConnection(url,user,password);

    }

    /**
     * 释放资源
     */
    public static void close(Statement stmt,Connection conn){
        //要分别抓取
        if (stmt != null){
            try {
                stmt.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
       if (conn != null){
           try {
               conn.close();
           } catch (SQLException throwables) {
               throwables.printStackTrace();
           }
       }
    }

    /**
     * 释放资源
     */
    public static void close(ResultSet rs, Statement stmt, Connection conn){
        //要分别抓取
        if (rs != null){
            try {
                rs.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
        if (stmt != null){
            try {
                stmt.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
        if (conn != null){
            try {
                conn.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
    }
}

• JDBCUtilsDemo

import jdk.nashorn.internal.scripts.JD;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

/**
 * @author :yangzhipeng
 * @date : 2023/3/9 10:15
 * Description :  演示JDBC工具类
 */

public class JDBCUtilsDemo {
    Connection conn= null;
    Statement stmt = null;
    ResultSet rs = null;

    public static void main(String[] args) {
        //用对象调用
        new JDBCUtilsDemo().test();
    }
    
    public void test(){
        try {
            conn = JDBCUtils.getConnection();
            String sql = "select * from t_user";
            stmt = conn.createStatement();
            rs = stmt.executeQuery(sql);
            while (rs.next()){
                String user_name = rs.getString("user_name");
                System.out.println(user_name);
            }
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }  finally {
            JDBCUtils.close(rs,stmt,conn);
        }
    }
}