0基础学java-day26(满汉楼实战）

一、界面设计

1. 需求说明

2 界面设计?

2.1 用户登录

2.2 显示餐桌状态

?2.3 预订

2.4 显示菜品

?2.5 点餐

2.6 查看账单

?2.7 结账

3 分层设计?

二、功能实现

1 工具类

1.1 构建如下的项目结构

1.2 导入相关的工具类和jar包

• 相关的工具类和jar包会放在评论区的百度网盘的链接中

1.3 整体项目结构

?1.4 相关sql语句，也就是要建立的表

#用户表
create table employee (
	id int primary key auto_increment, #自增
	empId varchar(50) not null default '',#员工号
	pwd char(32) not null default '',#密码md5
	name varchar(50) not null default '',#姓名
	job varchar(50) not null default '' #岗位
)charset=utf8; 

insert into employee values(null, '6668612', md5('123456'), '张三丰', '经理');
insert into employee values(null, '6668622', md5('123456'),'小龙女', '服务员');
insert into employee values(null, '6668633', md5('123456'), '张无忌', '收银员');
insert into employee values(null, '666', md5('123456'), '老韩', '经理');

#餐桌表
create table diningTable (
	id int primary key auto_increment, #自增, 表示餐桌编号
	state varchar(20) not null default '',#餐桌的状态
	orderName varchar(50) not null default '',#预订人的名字
	orderTel varchar(20) not null default ''
)charset=utf8; 

insert into diningTable values(null, '空','','');

#菜谱
create table menu (
	id int primary key auto_increment, #自增主键，作为菜谱编号(唯一)
	name varchar(50) not null default '',#菜品名称
	type varchar(50) not null default '', #菜品种类
	price double not null default 0#价格
)charset=utf8; 

insert into menu values(null, '八宝饭', '主食类', 10);
insert into menu values(null, '叉烧包', '主食类', 20);
insert into menu values(null, '宫保鸡丁', '热菜类', 30);
insert into menu values(null, '山药拨鱼', '凉菜类', 14);
insert into menu values(null, '银丝卷', '甜食类', 9);
insert into menu values(null, '水煮鱼', '热菜类', 26);
insert into menu values(null, '甲鱼汤', '汤类', 100);
insert into menu values(null, '鸡蛋汤', '汤类', 16);

#账单流水, 考虑可以分开结账, 并考虑将来分别统计各个不同菜品的销售情况
create table bill (
	id int primary key auto_increment, #自增主键
	billId varchar(50) not null default '',#账单号可以按照自己规则生成 UUID
	menuId int not null default 0,#菜品的编号, 也可以使用外键
	nums SMALLINT not null default 0,#份数
	money double not null default 0, #金额
	diningTableId int not null default 0, #餐桌
	billDate datetime not null ,#订单日期
	state varchar(50) not null default '' # 状态 '未结账' , '已经结账', '挂单'
)charset=utf8;

2 界面层?

package com.hspedu.mhl.view;

import com.hspedu.mhl.domain.*;
import com.hspedu.mhl.service.BillService;
import com.hspedu.mhl.service.DiningService;
import com.hspedu.mhl.service.EmployeeService;
import com.hspedu.mhl.service.MenuService;
import com.hspedu.mhl.utils.Utility;

import java.util.List;

/**
 * @author 林然
 * @version 1.0
 */
public class MHLView {

    //控制是否退出菜单
    private boolean loop =true;
    private String key="";//接收用户输入
    //定义一个employeeService对象
    private EmployeeService employeeService=new EmployeeService();
    //定义一个DiningTableService的属性
    DiningService diningService=new DiningService();
    //定义一个MenuService属性
    private MenuService menuService=new MenuService();

    //定义一个BillService属性
    BillService billService=new BillService();
    public static void main(String[] args) {
        new MHLView().mainMenue();
    }
    //显示所有餐桌状态
    public void listDiningTable(){
        List<DiningTable> list= diningService.list();
        System.out.println("\n餐桌编号\t\t 餐桌状态");
        for(DiningTable diningTable:list){
            System.out.println(diningTable);
        }
        System.out.println("显示完毕");
    }
    //预订餐桌
    public void book_table(int id){
        DiningTable diningTable=diningService.getDiningTableById(id);
        if (diningTable==null){
            System.out.println("餐桌号不存在，请重新预定");

        }else {
            if ("空".equals(diningTable.getState())){
                System.out.print("请确定是否预定y/n");
                String flag=Utility.readString(1);
                if("y".equals(flag)){
                    System.out.print("请输入预订人姓名");
                    String name=Utility.readString(10);
                    System.out.print("请输入预定人电话");
                    String tel=Utility.readString(20);
                    if (diningService.orderDiningTable(id,name,tel)){
                        System.out.println(id+"餐桌预定成功");
                    }else {
                        System.out.println(id+"餐桌预定失败");
                    }
                }else {
                    System.out.println("已取消预定");
                }
            }else {
                System.out.println("该餐桌已被预定，请重新预定");
            }
        }
    }

    //显示所有菜品
    public void  show_menu(){
        List<Menu> list= menuService.list();
        for (Menu menu:list){

            System.out.println(menu);
        }
    }
    //完成点餐
    public void ordermenu(){
        System.out.println("=============点餐服务==============");
        System.out.print("请输入点餐桌号(-1退出):");
        int orderDiningId=Utility.readInt();
        //如果orderDiningId为-1，那么取消
        if(orderDiningId==-1){
            System.out.println("=============取消点餐==============");
            return;
        }
        System.out.print("请输入点餐菜品号(-1退出):");
        int menuId=Utility.readInt();
        //如果menuId为-1，那么取消
        if(menuId==-1){
            System.out.println("=============取消点餐==============");
            return;
        }
        System.out.print("请输入点餐菜品量(-1退出):");
        int ordernums=Utility.readInt();
        //如果ordernums为-1，那么取消
        if(ordernums==-1){
            System.out.println("=============取消点餐==============");
            return;
        }

        //验证餐桌号是否存在
        DiningTable diningTable=diningService.getDiningTableById(orderDiningId);
        if(diningTable==null){
            System.out.println("=============餐桌号不存在==============");
            return;
        }
        //验证菜品
        Menu menu=menuService.getMenuById(menuId);
        if(menu==null){
            System.out.println("=============菜品不存在==============");
            return;
        }
        //点餐
        if(billService.orderMenu(menuId,ordernums,orderDiningId)){
            System.out.println("=============点餐成功==============");
        }else {
            System.out.println("=============点餐失败==============");
        }

    }
    //显示所有账单信息
    public void listBill(){
        System.out.println("\n编号\t\t菜品号\t\t菜品量\t\t金额\t\t桌号\t\t\t日期\t\t\t\t\t\t状态\t\t菜品名");
        List<MultiTableBean> Bills=billService.list2();
        for (MultiTableBean bill :Bills){
            System.out.println(bill);
        }
        System.out.println("=============显示完毕==============");
    }
    //结账
    public void paybill(){
        System.out.println("=============结账服务==============");
        System.out.print("请选择要结账的餐桌编号(-1退出)：");
        int diningTableId=Utility.readInt();
        if (diningTableId==-1){
            System.out.println("=============取消结账==============");
            return;
        }
        DiningTable diningTable=diningService.getDiningTableById(diningTableId);
        if(diningTable==null){
            System.out.println("=============结账餐桌不存在==============");
            return;
        }
        if(!billService.hasPayBillByDiningTableId(diningTableId)){
            System.out.println("=============该餐桌没有未结账账单==============");
            return;
        }
        System.out.print("结账方式(现金/微信/支付宝)表示退出：");
        String payMode=Utility.readString(10,"");//如果回车，就是返回""
        if("".equals(payMode)){
            System.out.println("=============取消结账==============");
            return;
        }
        char key=Utility.readConfirmSelection();
        if(key=='Y'){
            //结账
            if(billService.payBill(diningTableId,payMode)){
                System.out.println("=============结账成功==============");
            }else {
                System.out.println("=============结账失败==============");
            }
        }else {
            System.out.println("=============取消结账==============");
        }
    }
    public void mainMenue(){
        while (loop){
            System.out.println("=============满汉楼==============");
            System.out.println("\t\t 1 登录满汉楼");
            System.out.println("\t\t 2 退出满汉楼");
            System.out.print("请输入你的选择");
            key= Utility.readString(1);
            switch (key){
                case "1":
                    System.out.println("请输入员工号：");
                    String empId=Utility.readString(50);
                    System.out.println("请输入密码");
                    String pwd=Utility.readString(50);
                    Employee employee=employeeService.getEmployeeByIdAndPwd(empId,pwd);
                    if(employee!=null){//说明存在用户
                        System.out.println("============登录成功【" +employee.getName()+"】================");

                        //显示二级菜单，这里二级菜单是循环操作
                        while (loop){
                            System.out.println("=============满汉楼（二级菜单）==============");
                            System.out.println("\t\t 1 显示餐桌状态");
                            System.out.println("\t\t 2 预订餐桌");
                            System.out.println("\t\t 3 显示所有菜品");
                            System.out.println("\t\t 4 点餐服务");
                            System.out.println("\t\t 5 查看账单");
                            System.out.println("\t\t 6 结账");
                            System.out.println("\t\t 9 退出满汉楼");
                            System.out.print("请输入你的选择");
                            key=Utility.readString(1);
                            switch (key){
                                case "1":
                                    listDiningTable();
                                    break;
                                case "2":
                                    System.out.print("请输入你要预定的餐桌号");
                                    int id=Utility.readInt();
                                    book_table(id);
                                    break;
                                case"3":
                                    System.out.println("菜品编号\t\t菜品名\t\t类别\t\t\t价格");
                                    show_menu();
                                    System.out.print("显示完毕");
                                    break;
                                case"4":
                                    ordermenu();
                                    break;
                                case "5":
                                    listBill();
                                    break;
                                case"6":
                                    paybill();
                                    break;
                                case"9":
                                    loop=false;
                                    break;
                                default:
                                    System.out.println("你的输入有误吗，请重新输入");
                            }


                        }


                    }
                    else {
                        System.out.println("=============登录失败===========");
                    }

                    break;
                case "2":
                    System.out.println("退出满汉楼");
                    loop=false;
                    break;
                default:
                    System.out.println("你的输入有误，请重新输入");
            }

        }
    }
}

3 domain层

一个类就对应一张表，如果是多表查询，那就可以新建一个类来存储多表查询的信息‘

3.1 Employee

package com.hspedu.mhl.domain;

/**
 * @author 林然
 * @version 1.0
 * 这是一个javbean和employ对应
 */
public class Employee {
    private Integer id;
    private String empId;
    private String pwd;
    private String name;
    private String job;

    public Employee() {//无参构造器，底层apache-dbutils反射需要
    }

    public Employee(Integer id, String empId, String pwd, String name, String job) {
        this.id = id;
        this.empId = empId;
        this.pwd = pwd;
        this.name = name;
        this.job = job;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getEmpId() {
        return empId;
    }

    public void setEmpId(String empId) {
        this.empId = empId;
    }

    public String getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getJob() {
        return job;
    }

    public void setJob(String job) {
        this.job = job;
    }
}

3.2 DiningTable

package com.hspedu.mhl.domain;

/**
 * @author 林然
 * @version 1.0
 * 这是一个javabean 和 diningTable对应
 */
public class DiningTable {
    private Integer id;
    private String state;
    private String name;
    private String orderTel;

    public DiningTable() {
    }

    public DiningTable(Integer id, String state, String name, String orderTel) {
        this.id = id;
        this.state = state;
        this.name = name;
        this.orderTel = orderTel;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getState() {
        return state;
    }

    public void setState(String state) {
        this.state = state;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getOrderTel() {
        return orderTel;
    }

    public void setOrderTel(String orderTel) {
        this.orderTel = orderTel;
    }

    @Override
    public String toString() {
        return id +"\t\t\t"+state;
    }
}

3.3 Menu

package com.hspedu.mhl.domain;

/**
 * @author 林然
 * @version 1.0
 */
public class Menu {
    private Integer id;
    private String name;
    private String type;
    private Double price;

    public Menu() {
    }

    public Menu(Integer id, String name, String type, Double price) {
        this.id = id;
        this.name = name;
        this.type = type;
        this.price = price;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }

    public Double getPrice() {
        return price;
    }

    public void setPrice(Double price) {
        this.price = price;
    }

    @Override
    public String toString() {
        return id+"\t\t\t"+name+"\t\t"+type+"\t\t"+price;
    }
}

3.4 Bill

package com.hspedu.mhl.domain;

import java.util.Date;

/**
 * @author 林然
 * @version 1.0
 * Bill是一个javabean 和bill对应
 */
public class Bill {
    private Integer id;
    private String billId;
    private Integer menuId;
    private Integer nums;
    private Double money;
    private Integer diningTableId;
    private Date billDate;
    private String state;

    public Bill() {
    }

    public Bill(Integer id, String billId, Integer menuId, Integer nums, Double money, Integer diningTableId, Date billDate, String state) {
        this.id = id;
        this.billId = billId;
        this.menuId = menuId;
        this.nums = nums;
        this.money = money;
        this.diningTableId = diningTableId;
        this.billDate = billDate;
        this.state = state;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getBillId() {
        return billId;
    }

    public void setBillId(String billId) {
        this.billId = billId;
    }

    public Integer getMenuId() {
        return menuId;
    }

    public void setMenuId(Integer menuId) {
        this.menuId = menuId;
    }

    public Integer getNums() {
        return nums;
    }

    public void setNums(Integer nums) {
        this.nums = nums;
    }

    public Double getMoney() {
        return money;
    }

    public void setMoney(Double money) {
        this.money = money;
    }

    public Integer getDiningTableId() {
        return diningTableId;
    }

    public void setDiningTableId(Integer diningTableId) {
        this.diningTableId = diningTableId;
    }

    public Date getBillDate() {
        return billDate;
    }

    public void setBillDate(Date billDate) {
        this.billDate = billDate;
    }

    public String getState() {
        return state;
    }

    public void setState(String state) {
        this.state = state;
    }

    @Override
    public String toString() {
        return id+"\t\t"+menuId+"\t\t\t"+nums+
                "\t\t\t"+money+"\t"+diningTableId+"\t\t"+billDate+
                "\t\t"+state;
    }
}

3.5?MultiTableBean

package com.hspedu.mhl.domain;

import java.util.Date;

/**
 * @author 林然
 * @version 1.0
 * 这是一个javabean,可以和多张表进行对应
 */
public class MultiTableBean {
    private Integer id;
    private String billId;
    private Integer menuId;
    private Integer nums;
    private Double money;
    private Integer diningTableId;
    private Date billDate;
    private String state;
    //增加一个来自menu表的name
    private String name;
    //思考：这里的属性名是否要和列名保持一致--可以不一致，但是建议保持一致
    // -但是这里如果多表查询有相同名字--可以使用别名来解决
    public MultiTableBean() {
    }

    public MultiTableBean(Integer id, String billId, Integer menuId, Integer nums, Double money, Integer diningTableId, Date billDate, String state, String name) {
        this.id = id;
        this.billId = billId;
        this.menuId = menuId;
        this.nums = nums;
        this.money = money;
        this.diningTableId = diningTableId;
        this.billDate = billDate;
        this.state = state;
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getBillId() {
        return billId;
    }

    public void setBillId(String billId) {
        this.billId = billId;
    }

    public Integer getMenuId() {
        return menuId;
    }

    public void setMenuId(Integer menuId) {
        this.menuId = menuId;
    }

    public Integer getNums() {
        return nums;
    }

    public void setNums(Integer nums) {
        this.nums = nums;
    }

    public Double getMoney() {
        return money;
    }

    public void setMoney(Double money) {
        this.money = money;
    }

    public Integer getDiningTableId() {
        return diningTableId;
    }

    public void setDiningTableId(Integer diningTableId) {
        this.diningTableId = diningTableId;
    }

    public Date getBillDate() {
        return billDate;
    }

    public void setBillDate(Date billDate) {
        this.billDate = billDate;
    }

    public String getState() {
        return state;
    }

    public void setState(String state) {
        this.state = state;
    }

    @Override
    public String toString() {
        return id+"\t\t"+menuId+"\t\t\t"+nums+
                "\t\t\t"+money+"\t"+diningTableId+"\t\t"+billDate+
                "\t\t"+state+"\t\t"+name;
    }
}

4 DAO层

4.1 BasicDAO

package com.hspedu.mhl.dao;


import com.hspedu.mhl.utils.JDBCUtilsByDruid;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;

/**
 * @author 韩顺平
 * @version 1.0
 * 开发BasicDAO , 是其他DAO的父类
 */
public class BasicDAO<T> { //泛型指定具体类型

    private QueryRunner qr =  new QueryRunner();

    //开发通用的dml方法, 针对任意的表
    public int update(String sql, Object... parameters) {

        Connection connection = null;

        try {
            connection = JDBCUtilsByDruid.getConnection();
            int update = qr.update(connection, sql, parameters);
            return  update;
        } catch (SQLException e) {
           throw  new RuntimeException(e); //将编译异常->运行异常 ,抛出
        } finally {
            JDBCUtilsByDruid.close(null, null, connection);
        }

    }

    //返回多个对象(即查询的结果是多行), 针对任意表

    /**
     *
     * @param sql sql 语句，可以有 ?
     * @param clazz 传入一个类的Class对象 比如 Actor.class
     * @param parameters 传入 ? 的具体的值，可以是多个
     * @return 根据Actor.class 返回对应的 ArrayList 集合
     */
    public List<T> queryMulti(String sql, Class<T> clazz, Object... parameters) {

        Connection connection = null;
        try {
            connection = JDBCUtilsByDruid.getConnection();
            return qr.query(connection, sql, new BeanListHandler<T>(clazz), parameters);

        } catch (SQLException e) {
            throw  new RuntimeException(e); //将编译异常->运行异常 ,抛出
        } finally {
            JDBCUtilsByDruid.close(null, null, connection);
        }

    }

    //查询单行结果 的通用方法
    public T querySingle(String sql, Class<T> clazz, Object... parameters) {

        Connection connection = null;
        try {
            connection = JDBCUtilsByDruid.getConnection();
            return  qr.query(connection, sql, new BeanHandler<T>(clazz), parameters);

        } catch (SQLException e) {
            throw  new RuntimeException(e); //将编译异常->运行异常 ,抛出
        } finally {
            JDBCUtilsByDruid.close(null, null, connection);
        }
    }

    //查询单行单列的方法,即返回单值的方法

    public Object queryScalar(String sql, Object... parameters) {

        Connection connection = null;
        try {
            connection = JDBCUtilsByDruid.getConnection();
            return  qr.query(connection, sql, new ScalarHandler(), parameters);

        } catch (SQLException e) {
            throw  new RuntimeException(e); //将编译异常->运行异常 ,抛出
        } finally {
            JDBCUtilsByDruid.close(null, null, connection);
        }
    }

}

4.2 BillDAO

package com.hspedu.mhl.dao;

import com.hspedu.mhl.domain.Bill;

/**
 * @author 林然
 * @version 1.0
 */
public class BillDAO extends BasicDAO<Bill> {
}

4.3?DiningTableDAO

package com.hspedu.mhl.dao;

import com.hspedu.mhl.domain.DiningTable;

/**
 * @author 林然
 * @version 1.0
 */
public class DiningTableDAO extends BasicDAO<DiningTable> {
    //这里还可以写特有的操作
}

4.4?EmployeeDAO

package com.hspedu.mhl.dao;

import com.hspedu.mhl.domain.Employee;

/**
 * @author 林然
 * @version 1.0
 */
public class EmployeeDAO extends BasicDAO<Employee>{
    //这里还可以写特有的操作

}

4.5?MenuDAO

package com.hspedu.mhl.dao;

import com.hspedu.mhl.domain.Menu;

/**
 * @author 林然
 * @version 1.0
 */
public class MenuDAO extends BasicDAO<Menu> {
    //这里还可以写特有的操作
}

4.6?MultiTableDAO

package com.hspedu.mhl.dao;

import com.hspedu.mhl.domain.MultiTableBean;

/**
 * @author 林然
 * @version 1.0
 */
public class MultiTableDAO extends BasicDAO<MultiTableBean> {
}

5 Service层

5.1 BillService

package com.hspedu.mhl.service;

import com.hspedu.mhl.dao.BasicDAO;
import com.hspedu.mhl.dao.BillDAO;
import com.hspedu.mhl.dao.MultiTableDAO;
import com.hspedu.mhl.domain.Bill;
import com.hspedu.mhl.domain.MultiTableBean;

import java.util.List;
import java.util.UUID;

/**
 * @author 林然
 * @version 1.0
 * 处理和订单相关的业务逻辑
 */
public class BillService {
    //定义BillDAO属性
    private BillDAO billDAO=new BillDAO();
    //定义MenuSerVice属性
    private MenuService menuService=new MenuService();
    //定义DiningService
    private DiningService diningService=new DiningService();
    //定义MultiTableDAO类
    private MultiTableDAO multiTableDAO=new MultiTableDAO();
    //编写点餐方法
    //1 生成账单
    //2 更新对应餐桌状态
    public boolean orderMenu(int menuId,int nums,int diningTableId){
        //生成一个账单号,UUId
        String billID = UUID.randomUUID().toString();
        //将账单生成到bill表
        //要求计算账单金额，需要menuService来返回
        double price =menuService.getMenuById(menuId).getPrice();
        double money=price*nums;
        String sql ="insert into bill values(null,?,?,?,?,?,now(),'未结账')";
        int row= billDAO.update(sql,billID,menuId,nums,money,diningTableId);
        if(row<=0)
        {
            return false;
        }
        //需要更新餐桌状态
        return diningService.updateDiningTableState(diningTableId,"就餐中");


    }
    //返回所有账单列表
    public List<Bill> list(){
        return billDAO.queryMulti("select * from bill",Bill.class);
    }
    //返回所有账单列表
    public List<MultiTableBean> list2(){
        String sql="select bill.*,name from bill,menu where bill.menuId=menu.id";
        return multiTableDAO.queryMulti(sql,MultiTableBean.class);
    }
    //查看某个餐桌是否有未结账的菜单
    public boolean hasPayBillByDiningTableId(int diningTableId){
        String sql="select * from bill where diningTableId=? and state='未结账' limit 0,1";
        return billDAO.querySingle(sql,Bill.class,diningTableId)!=null;
    }
    //完成结账【如果餐桌存在，并且该餐桌有未结账的账单
    public boolean payBill(int diningTableId,String payMode ){
        //修改bill表
        String sql="update bill set state=? where diningTableId=? and state='未结账'";
        int row=billDAO.update(sql,payMode,diningTableId);
        if(row<=0)
            return false;
        //修改diningTable表
       // 注意：不要在这里直接操作，而应该在diningService进行操作
        if(!diningService.updateDiningTableStateToFree(diningTableId)){
            return false;
        }
        return true;
    }
}

5.2?DiningService

package com.hspedu.mhl.service;

import com.hspedu.mhl.dao.DiningTableDAO;
import com.hspedu.mhl.domain.DiningTable;

import java.util.List;

/**
 * @author 林然
 * @version 1.0
 */
public class DiningService {
    //定义一个DiningTableDAO对象
    private DiningTableDAO diningTableDAO=new DiningTableDAO();

    //返回所有餐桌信息
    public List<DiningTable> list(){
        String sql="select id,state from diningTable";
        return diningTableDAO.queryMulti(sql,DiningTable.class);
    }

    //订座 根据id查询对应的餐桌 DiningTable对象，如果返回空表示id编号对应的餐桌不存在
    public DiningTable getDiningTableById(int id){
        String sql ="select * from diningTable where id=?";
        DiningTable diningTable=diningTableDAO.querySingle(sql,DiningTable.class,id);
        return diningTable;
    }
    //如果餐桌可以预订，调用方法对其进行更新（包括预定人的名字和电话）
    public boolean orderDiningTable(int id,String name,String orderTel){
        String sql="update diningTable set state='已经预定',orderName=?,orderTel=? where id=?";
        int row= diningTableDAO.update(sql,name,orderTel,id);
        return row>0;
    }
    //需要提供一个更新餐桌状态的方法
    public boolean updateDiningTableState(int Id,String state){
        String sql="update diningTable set state=? where id=? ";
        int row= diningTableDAO.update(sql,state,Id);
        return row>0;
    }
    //提供方法，将指定的的餐桌设置为空闲状态
    public boolean updateDiningTableStateToFree(int Id){
        String sql="update diningTable set state='空',orderName='',orderTel='' where id=? ";
        int row= diningTableDAO.update(sql,Id);
        return row>0;
    }



}

5.3?EmployeeService

package com.hspedu.mhl.service;

import com.hspedu.mhl.dao.EmployeeDAO;
import com.hspedu.mhl.domain.Employee;

/**
 * @author 林然
 * @version 1.0
 * 该类对employee表的各种操作（通过调用EmployeeDAO对象完成）
 */
public class EmployeeService {
    //定义一个 EmployeeDAO 属性
    private EmployeeDAO employeeDAO=new EmployeeDAO();
    //方法，根据empId和pwd返回一个对象‘
    //如果查询不到，就返回null
    public Employee getEmployeeByIdAndPwd(String empId,String pwd){
        String sql="select * from employee where empId=? and pwd=md5(?)";
        Employee employee=employeeDAO.querySingle(sql,Employee.class,empId,pwd);
        return employee;
    }
}

5.4?MenuService

package com.hspedu.mhl.service;

import com.hspedu.mhl.dao.MenuDAO;
import com.hspedu.mhl.domain.Menu;

import java.util.List;

/**
 * @author 林然
 * @version 1.0
 */
public class MenuService {
    //定义一个 MenuDAO 属性
    private MenuDAO menuDAO=new MenuDAO();
    //显示所有菜品
    public List<Menu> list(){
        String sql="select * from menu";
        return menuDAO.queryMulti(sql,Menu.class);
    }
    public Menu getMenuById(int id){
        String sql="select * from menu where id=?";
        return menuDAO.querySingle(sql,Menu.class,id);
    }
}

三、演示视频