1.代码的实现

package com.yzy.sell.Service.Impl;
import com.yzy.sell.DTO.CateDTO;
import com.yzy.sell.DTO.OrderDTO;
import com.yzy.sell.Entity.OrderDetail;
import com.yzy.sell.Entity.OrderMaster;
import com.yzy.sell.Entity.ProductInfo;
import com.yzy.sell.Enums.OrderStatusEnum;
import com.yzy.sell.Enums.PayStatusEnum;
import com.yzy.sell.Enums.ResultEnum;
import com.yzy.sell.Repository.OrderDetailRepository;
import com.yzy.sell.Repository.OrderMasterRepository;
import com.yzy.sell.Repository.ProductInfoRepository;
import com.yzy.sell.Service.OrderService;
import com.yzy.sell.Service.ProductService;
import com.yzy.sell.exception.SellException;
import com.yzy.sell.utils.KeyUtil;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.List;
import java.util.stream.Collectors;

@Service
public class OrderServiceImpl implements OrderService {
    @Autowired
    private ProductInfoRepository productInfoRepository;
    @Autowired
    private  ProductService productService;
    @Autowired
    private OrderDetailRepository orderDetailRepository;
    @Autowired
    private OrderMasterRepository orderMasterRepository;

    @Override
    @Transactional  //添加此标签后，发生异常数据库会回滚操作
    public OrderDTO create(OrderDTO orderDTO) {
        String orderId= KeyUtil.genUniqueKey();
        List<OrderDetail> orderDetailList = orderDTO.getOrderDetailList();
        BigDecimal orderAmount=new BigDecimal(BigInteger.ZERO);
        //1.获取商品价格、名字
        for(OrderDetail orderDetail:orderDetailList){
            ProductInfo productInfo = productInfoRepository.findById(orderDetail.getProductId()).get();
            if(productInfo==null){
                new SellException(ResultEnum.PRODUCT_NO_EXIST);
            }
            //2.计算订单总价
            orderAmount=productInfo.getProductPrice().multiply(new BigDecimal(orderDetail.getProductQuantity()))
                        .add(orderAmount);

            //3.1写入订单详情（orderDetail）数据库
            orderDetail.setDetailId(KeyUtil.genUniqueKey());
            orderDetail.setOrderId(orderId);
            BeanUtils.copyProperties(productInfo,orderDetail);
            orderDetailRepository.save(orderDetail);
        }
        //3.2写入订单（orderMaster）数据库
        OrderMaster orderMaster=new OrderMaster();
        orderDTO.setOrderId(orderId);
        BeanUtils.copyProperties(orderDTO,orderMaster);
        orderMaster.setOrderAmount(orderAmount);
        orderMaster.setOrderStatus(OrderStatusEnum.NEW.getCode());
        orderMaster.setPayStatus(PayStatusEnum.WAIT.getCode());
        orderMasterRepository.save(orderMaster);
        //4.减库存
        List<CateDTO> cateDTOList=orderDetailList.stream().map(e-> new CateDTO(e.getProductId(),e.getProductQuantity()))
                .collect(Collectors.toList());
        productService.decreaseStock(cateDTOList);

        return orderDTO;
    }

2.关于@Transactional的使用

 

 3.关于lambda表达式的使用 

 

 

@Transactional