JDBC 练习

建立两个表，一个水果表一个用户表。

1.要求输入账号和密码，登陆成功显示欢迎界面，失败提示错误

2.显示选择界面，输入不同的数字，显示不同的内容，，并实现不同的功能，并返回界面

import java.awt.image.Raster;
import java.sql.*;
import java.util.*;public class ZuoYe {
   public static String zh;    public static void main(String [] args) throws Exception {
        Scanner sc=new Scanner(System.in);
        System.out.println("请输入账号");
         zh=sc.nextLine();
        System.out.println("请输入密码");
        String mm=sc.nextLine();        Class.forName("com.mysql.jdbc.Driver");        String jdbc="jdbc:mysql://127.0.0.1:3306/mydb";
        Connection conn=DriverManager.getConnection(jdbc, "root", "");
        String sql="select * from login where UserName=? and Password=? ";
        PreparedStatement state= conn.prepareStatement(sql);
        state.setString(1, zh);
        state.setString(2, mm);
        ResultSet re=state.executeQuery();        if(re.next()){
            System.out.println("登陆成功！"+re.getString(2)+",欢迎你！");
            jm();
        }
        else{
            System.out.println("账号或密码输入错误");
        }            conn.close();
    }    public static void jm() throws Exception{
        Scanner sc=new Scanner(System.in);
        System.out.println("************请选择服务项目***************");
        System.out.println("1.显示所有商品");
        System.out.println("2.添加商品");
        System.out.println("3.购买商品");
        System.out.println("4.退出");
        String xz=sc.nextLine();
        if(xz.equals("1")){
            xianshi();
            jm();
        }
        else if(xz.equals("2")){
            tianjia();
            xianshi();
            jm();
        }
        else if(xz.equals("3")){
            goumai();
            xianshi();
        }
        else if(xz.equals("4")){
            return;
        }
        else{
            System.out.println("输入有误");
        }
    }    public static void xianshi() throws Exception{
        Class.forName("com.mysql.jdbc.Driver");
        String jdbc="jdbc:mysql://127.0.0.1:3306/mydb";
        Connection conn=DriverManager.getConnection(jdbc, "root", "");
        String sql="select * from fruit";
        PreparedStatement state=conn.prepareStatement(sql);
        ResultSet re=state.executeQuery();
        System.out.println("*********************************************");
        System.out.println("商品编号"+"\t"+"商品名称"+"\t"+"单价"+"\t"+"原产地"+"\t"+"剩余商品数量");
        while(re.next()){
            System.out.println(re.getString(1)+"\t"+re.getString(2)+"\t"+re.getDouble(3)+"\t"+re.getString(4)+"\t"+re.getInt(5));
        }
        System.out.println("*********************************************");
        conn.close();
    }    public static void tianjia() throws Exception{
        Scanner sc=new Scanner(System.in);
        System.out.println("请输入商品属性:商品编号-商品名称-单价-原产地-添加数量，属性之间用-隔开");
        String sp=sc.nextLine();
        String [] str=sp.split("-");
        double qz=Double.parseDouble(str[2]) ;
        int sl=Integer.parseInt(str[4]);
        Class.forName("com.mysql.jdbc.Driver");
        String jdbc="jdbc:mysql://127.0.0.1:3306/mydb?characterEncoding=GBK";
        Connection conn=DriverManager.getConnection(jdbc, "root", "");
        String sql="insert into fruit values(?,?,?,?,?,NULL)";
        PreparedStatement state=conn.prepareStatement(sql);
        state.setString(1, str[0]);
        state.setString(2, str[1]);
        state.setDouble(3, qz);
        state.setString(4, str[3]);
        state.setInt(5, sl);
        state.executeUpdate();
        System.out.println("添加成功！！！");        conn.close();
    }    public static void goumai() throws Exception{
        Scanner sc=new Scanner(System.in);
        System.out.println("请输入购买的水果种类或代号");
        String mz=sc.nextLine();
        System.out.println("请输入购买数量");
        int sl=Integer.parseInt(sc.nextLine());        Class.forName("com.mysql.jdbc.Driver");
        String jdbc="jdbc:mysql://127.0.0.1:3306/mydb?characterEncoding=GBK";
        Connection conn=DriverManager.getConnection(jdbc,"root","");
        conn.setAutoCommit(false);        //查询苹果单价
        String sql2="select * from fruit where Name=? or Ids=?";
        PreparedStatement state=conn.prepareStatement(sql2);
        state.setString(1, mz);
        state.setString(2, mz);
        ResultSet re=state.executeQuery();
        re.next();
        double zj=re.getDouble(3)*sl;//总价格        //修改商品数量
        String sl_sql="update fruit set Numbers=? where Name=? or Ids=?";
        PreparedStatement state_sl=conn.prepareStatement(sl_sql);
        state_sl.setInt(1, (re.getInt(5)-sl));
        state_sl.setString(2, mz);
        state_sl.setString(3, mz);
        state_sl.executeUpdate();        //修改用户剩余钱数
        String sy="update login set Account=Account-? where UserName=?";
        PreparedStatement dstate=conn.prepareStatement(sy);
        dstate.setDouble(1, zj);
        dstate.setString(2, zh);
        dstate.executeUpdate();        //最后查询剩余钱数
        String zhye="select * from login where UserName=?";
        PreparedStatement state_ye=conn.prepareStatement(zhye);
        state_ye.setString(1, zh);
        ResultSet re1 =state_ye.executeQuery();
        re1.next();
        System.out.println("购买成功!!!您当前账户余额为"+re1.getDouble(4)+"元");
        conn.commit();
        conn.close();
    }}