一、將連接數據庫所需的相關信息寫入到配置文件、通過讀取配置文件來獲取數據庫的相關信息

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;

 
/**
 * [說明]:jdbc工具類
 * 封裝了jdbc裏面的重復步驟:數據庫的連接和數據庫資源的釋放
 * @author aeon
 * @version 1.2(該版本將連接數據庫的各種數據庫配置信息(用戶名、密碼、驅動及url)單獨提取到配置文件中)
 */
public class AeonJdbcUtils {
    private static String username;
    private static String password;
    private static String driverClass;
    private static
 
 String url;
    /**
     * 靜態代碼塊處理讀取之前的數據
     */
    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("初始化讀取數據庫配置文件--->database.properties失敗！");
            e.printStackTrace();
        }
    }
    /**
     * 連接數據庫
     * @return 數據庫連接對象
     * @throws ClassNotFoundException
     * @throws SQLException
     */
    public static Connection getMySqlConnection() throws ClassNotFoundException, SQLException{
        Class.forName(driverClass);
        return DriverManager.getConnection(url, username, password);
    }
    /**
     * 釋放數據庫資源
     * @param resultSet 結果集
     * @param statement 執行sql語句的對象
     * @param connection 數據庫連接對象
     */
    public static void closeDB(ResultSet resultSet,Statement statement,Connection connection){
        if(null!=resultSet){
            try {
                resultSet.close();
            } catch (SQLException e) {
                System.out.println("釋放數據庫資源失敗！--->resultSet");
                e.printStackTrace();
            }
        }
        if(null!=statement){
            try {
                statement.close();
            } catch (SQLException e) {
                System.out.println("釋放數據庫資源失敗！--->statement");
                e.printStackTrace();
            }
        }
        if(null!=connection){
            try {
                connection.close();
            } catch (SQLException e) {
                System.out.println("釋放數據庫資源失敗！--->connection");
                e.printStackTrace();
            }
        }
    }
}

測試代碼:　　

package edu.aeon.aeonutils;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
/**
 * [說明]:測試連接數據庫工具類(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("用戶id\t用戶名\t用戶密碼");
            while (resultSet.next()) {
                int userId = resultSet.getInt("userId");// 根據表字段名獲取該行記錄上的字段名所對應的字段值
                String userName = resultSet.getString("userName");
                String userPw = resultSet.getString("userpw");// 數據庫中的字段不區分大小寫
                System.out.println(userId + "\t" + userName + "\t" + userPw);
            }
        } catch (ClassNotFoundException e) {
            System.out.println("加載驅動失敗!");
            e.printStackTrace();
        } catch (SQLException e) {
            System.out.println("連接數據庫失敗!");
            e.printStackTrace();
        }
        AeonJdbcUtils.closeDB(resultSet, statement, connection);
    }
}

database.properties中的配置信息：　　

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

項目包視圖截圖如下：

建庫及表語句：　　

drop database db_test;
create database db_test;
use db_test;
create table user(
    userId int(5) primary key comment ‘用戶id‘,
    userName varchar(16) comment ‘用戶姓名‘,
    userPw varchar(16) comment ‘用戶密碼‘
);
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‘);

數據庫信息截圖：　　

測試結果截圖：

dljd_011_jdbc再次封裝工具類_把數據庫的相關信息寫到配置文件中,減低代碼的耦合度