生成订单：三个表（Products，Orders，OrderItem）

1.有三个表（Product上，Orders，OrderItem）

分别创建对应的三个实体类

OrderItem中有外键Order_id 参考Orders中的id ；Product_id参考Product中的id；Orders中有外键User_id参考User中的id

sql 代码：

CREATE DATABASE day2017_04_05;
USE day2017_04_05;
CREATE TABLE `user` (
  `id` INT(11) AUTO_INCREMENT,
  `username` VARCHAR(20) ,
  `PASSWORD` VARCHAR(20) ,
  `gender` VARCHAR(10) ,
  `email` VARCHAR(50) ,
  `telephone` VARCHAR(20) ,
  `introduce` VARCHAR(100),
  `activeCode` VARCHAR(50) ,
  `state` INT(11) ,
  `role` VARCHAR(10) DEFAULT '普通用户',
  `registTime` TIMESTAMP ,
  PRIMARY KEY (`id`)
)
商品表
CREATE TABLE `products` (
  `id` VARCHAR(100) ,
  `name` VARCHAR(40) ,
  `price` DOUBLE ,
  `category` VARCHAR(40) ,
  `pnum` INT(11) ,
  `imgurl` VARCHAR(100) ,
  `description` VARCHAR(255) ,
  PRIMARY KEY (`id`)
)
订单表
CREATE TABLE `orders` (
  `id` VARCHAR(100) ,
  `money` DOUBLE ,
  `receiverAddress` VARCHAR(255) ,
  `receiverName` VARCHAR(20) ,
  `receiverPhone` VARCHAR(20) ,
  `paystate` INT(11) ,
  `ordertime` TIMESTAMP ,
  `user_id` INT(11) ,
  PRIMARY KEY (`id`),
  FOREIGN KEY (`user_id`) REFERENCES `user` (`id`)
)
订单项表
CREATE TABLE `orderitem` (
  `order_id` VARCHAR(100) ,
  `product_id` VARCHAR(100),
  `buynum` INT(11) ,
  PRIMARY KEY (`order_id`,`product_id`),
  FOREIGN KEY (`order_id`) REFERENCES `orders` (`id`),
  FOREIGN KEY (`product_id`) REFERENCES `products` (`id`)
)

实体类

public class Order {
    private String id; // 订单编号
    private double money; // 订单总价
    private String receiverAddress; // 送货地址
    private String receiverName; // 收货人姓名
    private String receiverPhone; // 收货人电话
    private int paystate; // 订单状态
    private Date ordertime; // 下单时间
    private int userid;
    private List<OrderItem> orderItems;
}

public class OrderItem {
    private Order order;//订单
    private Product product; //商品
    private int buynum; //购物数量
    }

public class Product {
    private String id; // 商品编号
    private String name; // 名称
    private double price; // 价格
    private String category; // 分类
    private int pnum; // 数量
    private String imgurl; // 图片路径
    private String description; // 描述
    }
    

servlet 操作

package com.learning.web.servlet;

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.Map;
import java.util.UUID;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.beanutils.BeanUtils;

import com.learning.domain.Order;
import com.learning.domain.OrderItem;
import com.learning.domain.Product;
import com.learning.domain.User;
import com.learning.service.OrderService;

@WebServlet("/createOrder")
public class CreateOrderServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

            Order order=new  Order();
            User user = (User) request.getSession().getAttribute("user");
            try {
                BeanUtils.populate(order, request.getParameterMap());
                order.setId(UUID.randomUUID().toString());
                order.setUserid(user.getId());
            } catch (Exception e) {
                e.printStackTrace();
            }

            List<OrderItem> orderItems=new ArrayList<OrderItem>();
            //从session中获取cart，添加到订单项中
            Map<Product, String> cart = (Map<Product, String>) request.getSession().getAttribute("cart");
            for (Map.Entry<Product, String> map : cart.entrySet()) {
                OrderItem orderItem=new OrderItem();
                orderItem.setBuynum(Integer.parseInt(map.getValue()));
                orderItem.setProduct(map.getKey());
                orderItem.setOrder(order);
                orderItems.add(orderItem);
            }

            order.setOrderItems(orderItems);
            OrderService orderService=new OrderService();
            orderService.createOrder(order);
            //生成订单，删除cart中的所有product
            cart.clear();

            request.getRequestDispatcher("/pay.jsp").forward(request, response);

    }
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

}

    public void createOrder(Order order) {
        try {

            ManageTheadLocal.startTransaction();
            orderDao.createOrder(order);
            orderItemDao.createOrderItem(order);
            productDao.updateProductNumber(order);
            ManageTheadLocal.commit();
        } catch (SQLException e) {
            ManageTheadLocal.rollback();
            e.printStackTrace();
        }
    }

public void createOrder(Order order) throws SQLException {
        QueryRunner queryRunner=new QueryRunner(C3P0Util.getDataSource());
        queryRunner.update(ManageTheadLocal.getConnection()," insert into orders values(?,?,?,?,?,?,?,?)",order.getId(),order.getMoney(),order.getReceiverAddress(),order.getReceiverName(),order.getReceiverPhone(),order.getPaystate(),order.getOrdertime(),order.getUserid());

    }

public void createOrderItem(Order order) throws SQLException {
            List<OrderItem> orderItems = order.getOrderItems();
            QueryRunner queryRunner=new QueryRunner(C3P0Util.getDataSource());
            Object[][] params =new Object[orderItems.size()][];
            for (int i = 0; i < params.length; i++) {
                params[i]=new Object[]{order.getId(),orderItems.get(i).getProduct().getId(),orderItems.get(i).getBuynum()};
            }
            queryRunner.batch(ManageTheadLocal.getConnection()," insert into orderitem values (?,?,?) ",params );
    }

public void updateProductNumber(Order order) throws SQLException {
        List<OrderItem> orderItems = order.getOrderItems();
        QueryRunner queryRunner=new QueryRunner(C3P0Util.getDataSource());

        Object[][] params=new Object[orderItems.size()][];
        for (int i = 0; i < params.length; i++) {
            params[i]=new Object[]{orderItems.get(i).getBuynum()};
        }
        queryRunner.batch(ManageTheadLocal.getConnection()," update products set pnum=pnum-?", params);
    }