数据库的连接与简单的ATM增删查改操作

连接数据库有两种方式，直连和桥连，这里作者只讲一下普遍的直连，桥连读者想知道请自行百度

首先要有驱动软件，笔者的工具很旧



在你的java项目里面创建一个文件夹lib,将jar文件复制到里面，右键点击jar文件→Build Path→Configure Build Path→


添加找到lib目录下的jar文件 确定

则会出现奶瓶，这样驱动就弄好的，下面开始连接





请注意里面所有的包都是java.sql下的 ，其中root是你的mysql账号，610321520是你的mysql的密码，3306是mysql的端口号，localhost是回文地址也可写为127.0.0.1

//加载驱动

Class.forName("com.mysql.jdbc.Driver");

//注册驱动

Connection coo=DriverManager.getConnection("jdbc:mysql://localhost:3306/school","root","610321520");

//产生语句处理对象

Statement sta=coo.createStatement();；连接数据库的重要组成部分

下面就是我做的一个简单的ATM连接数据库

首先在mysql里面创建书库

CREATE DATABASE bank

USE bank

CREATE TABLE users(

u_id INT,

u_name VARCHAR(50),

u_password INT,

u_money DOUBLE)

INSERT INTO users VALUES(1,'小王',111,5000)

INSERT INTO users VALUES(2,'小花',222,5000)

INSERT INTO users VALUES(3,'小明',333,5000)

下面是java代码

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

import java.util.Scanner;

public class ATM {

public static void main(String[] args) {

Connection con = null;

Statement sta = null;

ResultSet rs = null;

int yh;

int mm;

try {

Class.forName("com.mysql.jdbc.Driver");

} catch (ClassNotFoundException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

String url = "jdbc:mysql://localhost:3306/bank";

try {

System.out.println("系统正常运行");

con = DriverManager.getConnection(url, "root", "610321520");

// System.out.println(con);

sta = con.createStatement();

System.out.println("欢迎来到中国银行");

int count = 0;

while(true) {

System.out.println("请输入账号");

Scanner in = new Scanner(System.in);

yh = in.nextInt();

System.out.println("请输入密码");

Scanner in1 = new Scanner(System.in);

mm = in.nextInt();

String sql = "select * from users where u_id = '"+yh+"' and u_password = '"+mm+"'";

rs = sta.executeQuery(sql);

if(rs.next()) {

break;

}else {

count ++ ;

if(count == 3) {

System.out.println("您输入的次数已超过安全次数，请携带有效证件去柜台取卡");

System.exit(0);

}else {

System.out.println("用户名或密码不正确!");

}

}

}

while(true) {

String s = "select u_name from users where u_id = '"+yh+"'";

rs = sta.executeQuery(s);

String name = null ;

if(rs.next()) {

name = rs.getString("u_name");

System.out.println(name+"先生您好！请选择操作按钮：1.存款 2.取款 3.查询余额 4.修改密码 5.转账 6.退卡");

}

Scanner in = new Scanner(System.in);

int flag = in.nextInt();

if(flag == 1) {

System.out.println("请输入您的存款金额");

Scanner in1 = new Scanner(System.in);

int c_money = in1.nextInt();

String sql = "update users set u_money=u_money + '"+c_money+"' where u_id='"+yh+"'";

sta.executeUpdate(sql);

System.out.println("存款成功");

}else if(flag == 2) {

System.out.println("请输入你的取款金额");

Scanner in1 = new Scanner(System.in);

int q_money =in1.nextInt();

String sql1 = "select u_money from users where u_id='"+yh+"'";

rs = sta.executeQuery(sql1);

int money = 0 ;

while(rs.next()) {

money = rs.getInt(1);

}

if(money >= q_money) {

String sql = "update users set u_money=u_money - '"+q_money+"' where u_id='"+yh+"'";

sta.executeUpdate(sql);

System.out.println("取款成功");

}else {

System.out.println("您的余额不足，请查询余额");

}

}else if(flag == 3) {

String sql1 = "select u_money from users where u_id='"+yh+"'";

rs = sta.executeQuery(sql1);

int money = 0 ;

while(rs.next()) {

money = rs.getInt(1);

}

System.out.println("您的余额为：" + money + "元");

}else if(flag == 4) {

System.out.println("请输入旧密码");

Scanner in1 = new Scanner(System.in);

int jmm = in1.nextInt();

if(jmm == mm) {

System.out.println("请输入新密码");

Scanner in2 = new Scanner(System.in);

int xmm = in1.nextInt();

String sql = "update users set u_password='"+xmm+"' where u_id='"+yh+"'";

sta.executeUpdate(sql);

System.out.println("修改密码成功");

}else {

System.out.println("您输入的密码有误，请重新输入");

}

}else if(flag == 5) {

System.out.println("请输入您要转帐的用户");

Scanner in1 = new Scanner(System.in);

String zh1 = in1.next();

System.out.println("请再次输入您要转帐的用户");

Scanner in2 = new Scanner(System.in);

String zh2 = in1.next();

if(zh1.equals(zh2)) {

String sql = "select u_name from users where u_id='"+yh+"'";

rs = sta.executeQuery(sql);

if(rs.next()) {

System.out.println("请输入您要转账的金额");

Scanner in3 = new Scanner(System.in);

int z_money = in3.nextInt();

String sql1 = "select u_money from users where u_id='"+yh+"'";

rs = sta.executeQuery(sql1);

int money = 0 ;

while(rs.next()) {

money = rs.getInt(1);

}

if(money >= z_money) {

String sql2 = "update users set u_money = u_money-'"+z_money+"' where u_id='"+yh+"'";

sta.executeUpdate(sql2);

String sql3 = "update users set u_money = u_money+'"+z_money+"' where u_id='"+zh1+"'";

sta.executeUpdate(sql3);

System.out.println("转账成功");

}else {

System.out.println("您的余额不足");

}

}else {

System.out.println("您输入的账户不存在");

}

}else {

System.out.println("您输入的账户不一致，请重新输入");

}

}else if(flag == 6) {

System.out.println("谢谢使用！");

System.exit(0);

}else {

System.out.println("暂未开通此服务，敬请期待！");

}

}

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}finally{

try {

if(rs != null) {

rs.close();

}

if(sta != null) {

sta.close();

}

if(con != null) {

con.close();

}

}catch (SQLException e) {

e.printStackTrace();

}

}

}

}