dljd_011_jdbc再次封装工具类_把数据库的相关信息写到配置文件中,减低代码的耦合度

package edu.aeon.aeonutils;

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

/**
 * [说明]:jdbc工具类
 * 封装了jdbc里面的重复步骤:数据库的连接和数据库资源的释放
 * @author aeon
 * @version 1.2(该版本将连接数据库的各种数据库配置信息(用户名、密码、驱动及url)单独提取到配置文件中)
 */
public class AeonJdbcUtils {
    private static String username;
    private static String password;
    private static String driverClass;
    private static String url;
    /**
     * 静态代码块处理读取之前的数据
     */
    static{
        InputStream inputStream = AeonJdbcUtils.class.getClassLoader().getResourceAsStream("config/database/database.properties");
        Properties properties=new Properties();
        try {
            properties.load(inputStream);
            username = properties.getProperty("username");
            password = properties.getProperty("password");
            driverClass = properties.getProperty("driverClass");
            url = properties.getProperty("url");
        } catch (IOException e) {
            System.out.println("初始化读取数据库配置文件--->database.properties失败！");
            e.printStackTrace();
        }
    }
    /**
     * 连接数据库
     * @return 数据库连接对象
     * @throws ClassNotFoundException
     * @throws SQLException
     */
    public static Connection getMySqlConnection() throws ClassNotFoundException, SQLException{
        Class.forName(driverClass);
        return DriverManager.getConnection(url, username, password);
    }
    /**
     * 释放数据库资源
     * @param resultSet 结果集
     * @param statement 执行sql语句的对象
     * @param connection 数据库连接对象
     */
    public static void closeDB(ResultSet resultSet,Statement statement,Connection connection){
        if(null!=resultSet){
            try {
                resultSet.close();
            } catch (SQLException e) {
                System.out.println("释放数据库资源失败！--->resultSet");
                e.printStackTrace();
            }
        }
        if(null!=statement){
            try {
                statement.close();
            } catch (SQLException e) {
                System.out.println("释放数据库资源失败！--->statement");
                e.printStackTrace();
            }
        }
        if(null!=connection){
            try {
                connection.close();
            } catch (SQLException e) {
                System.out.println("释放数据库资源失败！--->connection");
                e.printStackTrace();
            }
        }
    }
}

package edu.aeon.aeonutils;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
/**
 * [说明]:测试连接数据库工具类(version 1.2)
 * @author aeon
 *
 */
public class TestAeonJdbcUtils {
    public static void main(String[] args) {
        Connection connection = null;
        Statement statement = null;
        ResultSet resultSet = null;
        try {
            connection = AeonJdbcUtils.getMySqlConnection();
            statement = connection.createStatement();
            String sql = "select * from user";
            resultSet = statement.executeQuery(sql);
            System.out.println("用户id\t用户名\t用户密码");
            while (resultSet.next()) {
                int userId = resultSet.getInt("userId");// 根据表字段名获取该行记录上的字段名所对应的字段值
                String userName = resultSet.getString("userName");
                String userPw = resultSet.getString("userpw");// 数据库中的字段不区分大小写
                System.out.println(userId + "\t" + userName + "\t" + userPw);
            }
        } catch (ClassNotFoundException e) {
            System.out.println("加载驱动失败!");
            e.printStackTrace();
        } catch (SQLException e) {
            System.out.println("连接数据库失败!");
            e.printStackTrace();
        }
        AeonJdbcUtils.closeDB(resultSet, statement, connection);
    }
}

 username=root
 password=root
 driverClass=com.mysql.jdbc.Driver
 url=jdbc:mysql://localhost:3306/db_test

drop database db_test;
create database db_test;
use db_test;
create table user(
    userId int(5) primary key comment ‘用户id‘,
    userName varchar(16) comment ‘用户姓名‘,
    userPw varchar(16) comment ‘用户密码‘
);
insert into user(userId,userName,userPw) values(10001,‘user1‘,‘user1‘);
insert into user(userId,userName,userPw) values(10002,‘user2‘,‘user2‘);
insert into user(userId,userName,userPw) values(10003,‘user3‘,‘user3‘);
insert into user(userId,userName,userPw) values(10004,‘user4‘,‘user4‘);
insert into user(userId,userName,userPw) values(10005,‘user5‘,‘user5‘);