smbms超市管理项目-项目建立，数据库工具类编写

1、首先用maven工具创建项目

2、配置相关的properties驱动文件

driver=com.mysql.jdbc.Driver

url=jdbc:mysql://localhost:3306/smbms?useUnicode=true&useCharacterEncoding=utf8&useSSL=false

username=root

password=123456

3、Dao层编写基础的工具类

package com.liu.dao;

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

public class BasicDao {

    private static String driver;
    private static String url;
    private static String username;
    private static String password;

    static{

        InputStream res = BasicDao.class.getClassLoader().getResourceAsStream("db.properties");

        Properties pr = new Properties();

        try {
            pr.load(res);

        } catch (IOException e) {
            e.printStackTrace();
        }

        driver = pr.getProperty("driver");
        url = pr.getProperty("url");
        username = pr.getProperty("username");
        password = pr.getProperty("password");
    }

    public static Connection getConnection(){
        Connection connection = null;
        try {
            Class.forName(driver);
            connection = DriverManager.getConnection(url,username,password);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return connection;
    }

    //查询数据
    public static ResultSet execute(Connection co,ResultSet res,PreparedStatement prep,String sql,
                                    Object[] para){

        try {
            prep = co.prepareStatement(sql);
            for (int i = 0; i < para.length; i++) {
                prep.setObject(i+1,para[i]);
            }

            res = prep.executeQuery();

        } catch (SQLException e) {
            e.printStackTrace();
        }
        return res;
    }

    //增删改、函数重载机制
    public static int execute(Connection co,PreparedStatement prep,String sql,Object[] objects){
        int i = 0;
        try {
            prep = co.prepareStatement(sql);
            for (int j = 0; j < objects.length; j++) {
                prep.setObject(j+1,objects[j]);
            }
            i = prep.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return i;
    }

    //释放资源
    public static boolean closeResource(Connection connection,PreparedStatement preparedStatement,ResultSet resultSet){
        boolean flag = true;
        if (connection != null) {
            try {
                connection.close();
//                GC回收
                connection = null;
            } catch (SQLException e) {
                flag = false;
                e.printStackTrace();
            }
        }
        if (preparedStatement != null) {
            try {
                preparedStatement.close();
                preparedStatement = null;
            } catch (SQLException e) {
                flag = false;
                e.printStackTrace();
            }
        }
        if (resultSet != null) {
            try {
                resultSet.close();
//                垃圾回收机制回收
                resultSet = null;
            } catch (SQLException e) {
                flag = false;
                e.printStackTrace();
            }

        }

        return flag;
    }
}