Java 篇-项目实战-天机学堂(从0到1)-day12

java 篇： 1.基础地基 2.设计原理 3.项目实战

这章功力有点不足了，先放放，改日再会会。

定义优惠券规则业务流程分析及实现优惠规则：

策略模式，导包

定义接口：

因为是给其他服务用的，那得放在 api 模块下

和下面 FallbackConfig 当中对应

优惠券方案推荐 ComplateFuture 并发运算：

添加线程池

筛选最优解：

核心代码：

package com.tianji.promotion.service.impl; import com.tianji.api.dto.promotion.CouponDiscountDTO; import com.tianji.api.dto.promotion.OrderCouponDTO; import com.tianji.api.dto.promotion.OrderCourseDTO; import com.tianji.common.utils.CollUtils; import com.tianji.common.utils.UserContext; import com.tianji.promotion.domain.po.Coupon; import com.tianji.promotion.domain.po.CouponScope; import com.tianji.promotion.enums.UserCouponStatus; import com.tianji.promotion.mapper.UserCouponMapper; import com.tianji.promotion.service.ICouponScopeService; import com.tianji.promotion.service.IDiscountService; import com.tianji.promotion.strategy.discount.Discount; import com.tianji.promotion.strategy.discount.DiscountStrategy; import com.tianji.promotion.utils.PermuteUtil; import lombok.RequiredArgsConstructor; import lombok.extern.slf4j.Slf4j; import org.springframework.stereotype.Service; import java.util.*; import java.util.concurrent.CompletableFuture; import java.util.concurrent.CountDownLatch; import java.util.concurrent.Executor; import java.util.concurrent.TimeUnit; import java.util.stream.Collectors; @Slf4j @Service @RequiredArgsConstructor public class DiscountServiceImpl implements IDiscountService { private final UserCouponMapper userCouponMapper; private final ICouponScopeService scopeService; private final Executor discountSolutionExecutor; @Override public List<CouponDiscountDTO> findDiscountSolution(List<OrderCourseDTO> orderCourses) { // 1.查询我的所有可用优惠券 List<Coupon> coupons = userCouponMapper.queryMyCoupons(UserContext._getUser_()); if (CollUtils._isEmpty_(coupons)) { return CollUtils._emptyList_(); } // 2.初筛 // 2.1.计算订单总价 int totalAmount = orderCourses.stream().mapToInt(OrderCourseDTO::getPrice).sum(); // 2.2.筛选可用券 List<Coupon> availableCoupons = coupons.stream() .filter(c -> DiscountStrategy._getDiscount_(c.getDiscountType()).canUse(totalAmount, c)) .collect(Collectors._toList_()); if (CollUtils._isEmpty_(availableCoupons)) { return CollUtils._emptyList_(); } // 3.排列组合出所有方案 // 3.1.细筛（找出每一个优惠券的可用的课程，判断课程总价是否达到优惠券的使用需求） Map<Coupon, List<OrderCourseDTO>> availableCouponMap = findAvailableCoupon(availableCoupons, orderCourses); if (CollUtils._isEmpty_(availableCouponMap)) { return CollUtils._emptyList_(); } // 3.2.排列组合 availableCoupons = new ArrayList<>(availableCouponMap.keySet()); List<List<Coupon>> solutions = PermuteUtil._permute_(availableCoupons); // 3.3.添加单券的方案 for (Coupon c : availableCoupons) { solutions.add(List._of_(c)); } // 4.计算方案的优惠明细 List<CouponDiscountDTO> list = Collections._synchronizedList_(new ArrayList<>(solutions.size())); // 4.1.定义闭锁 CountDownLatch latch = new CountDownLatch(solutions.size()); for (List<Coupon> solution : solutions) { // 4.2.异步计算 CompletableFuture ._supplyAsync_( () -> calculateSolutionDiscount(availableCouponMap, orderCourses, solution), discountSolutionExecutor ).thenAccept(dto -> { // 4.3.提交任务结果 list.add(dto); latch.countDown(); }); } // 4.4.等待运算结束 try { latch.await(1, TimeUnit._SECONDS_); } catch (InterruptedException e) { _log_.error("优惠方案计算被中断，{}", e.getMessage()); } // 5.筛选最优解 return findBestSolution(list); } @Override public CouponDiscountDTO queryDiscountDetailByOrder(OrderCouponDTO orderCouponDTO) { // 1.查询用户优惠券 List<Long> userCouponIds = orderCouponDTO.getUserCouponIds(); List<Coupon> coupons = userCouponMapper.queryCouponByUserCouponIds(userCouponIds, UserCouponStatus._UNUSED_); if (CollUtils._isEmpty_(coupons)) { return null; } // 2.查询优惠券对应课程 Map<Coupon, List<OrderCourseDTO>> availableCouponMap = findAvailableCoupon(coupons, orderCouponDTO.getCourseList()); if (CollUtils._isEmpty_(availableCouponMap)) { return null; } // 3.查询优惠券规则 return calculateSolutionDiscount(availableCouponMap, orderCouponDTO.getCourseList(), coupons); } private List<CouponDiscountDTO> findBestSolution(List<CouponDiscountDTO> list) { // 1.准备Map记录最优解 Map<String, CouponDiscountDTO> moreDiscountMap = new HashMap<>(); Map<Integer, CouponDiscountDTO> lessCouponMap = new HashMap<>(); // 2.遍历，筛选最优解 for (CouponDiscountDTO solution : list) { // 2.1.计算当前方案的id组合 String ids = solution.getIds().stream() .sorted(Long::_compare_).map(String::_valueOf_).collect(Collectors._joining_(",")); // 2.2.比较用券相同时，优惠金额是否最大 CouponDiscountDTO best = moreDiscountMap.get(ids); if (best != null && best.getDiscountAmount() >= solution.getDiscountAmount()) { // 当前方案优惠金额少，跳过 continue; } // 2.3.比较金额相同时，用券数量是否最少 best = lessCouponMap.get(solution.getDiscountAmount()); int size = solution.getIds().size(); if (size > 1 && best != null && best.getIds().size() <= size) { // 当前方案用券更多，放弃 continue; } // 2.4.更新最优解 moreDiscountMap.put(ids, solution); lessCouponMap.put(solution.getDiscountAmount(), solution); } // 3.求交集 Collection<CouponDiscountDTO> bestSolutions = CollUtils ._intersection_(moreDiscountMap.values(), lessCouponMap.values()); // 4.排序，按优惠金额降序 return bestSolutions.stream() .sorted(Comparator._comparingInt_(CouponDiscountDTO::getDiscountAmount).reversed()) .collect(Collectors._toList_()); } private CouponDiscountDTO calculateSolutionDiscount( Map<Coupon, List<OrderCourseDTO>> couponMap, List<OrderCourseDTO> courses, List<Coupon> solution) { // 1.初始化DTO CouponDiscountDTO dto = new CouponDiscountDTO(); // 2.初始化折扣明细的映射 Map<Long, Integer> detailMap = courses.stream().collect(Collectors._toMap_(OrderCourseDTO::getId, oc -> 0)); dto.setDiscountDetail(detailMap); // 3.计算折扣 for (Coupon coupon : solution) { // 3.1.获取优惠券限定范围对应的课程 List<OrderCourseDTO> availableCourses = couponMap.get(coupon); // 3.2.计算课程总价(课程原价 - 折扣明细) int totalAmount = availableCourses.stream() .mapToInt(oc -> oc.getPrice() - detailMap.get(oc.getId())).sum(); // 3.3.判断是否可用 Discount discount = DiscountStrategy._getDiscount_(coupon.getDiscountType()); if (!discount.canUse(totalAmount, coupon)) { // 券不可用，跳过 continue; } // 3.4.计算优惠金额 int discountAmount = discount.calculateDiscount(totalAmount, coupon); // 3.5.计算优惠明细 calculateDiscountDetails(detailMap, availableCourses, totalAmount, discountAmount); // 3.6.更新DTO数据 dto.getIds().add(coupon.getCreater()); dto.getRules().add(discount.getRule(coupon)); dto.setDiscountAmount(discountAmount + dto.getDiscountAmount()); } return dto; } private void calculateDiscountDetails(Map<Long, Integer> detailMap, List<OrderCourseDTO> courses, int totalAmount, int discountAmount) { int times = 0; int remainDiscount = discountAmount; for (OrderCourseDTO course : courses) { // 更新课程已计算数量 times++; int discount = 0; // 判断是否是最后一个课程 if (times == courses.size()) { // 是最后一个课程，总折扣金额 - 之前所有商品的折扣金额之和 discount = remainDiscount; } else { // 计算折扣明细（课程价格在总价中占的比例，乘以总的折扣） discount = discountAmount * course.getPrice() / totalAmount; remainDiscount -= discount; } // 更新折扣明细 detailMap.put(course.getId(), discount + detailMap.get(course.getId())); } } private Map<Coupon, List<OrderCourseDTO>> findAvailableCoupon( List<Coupon> coupons, List<OrderCourseDTO> courses) { Map<Coupon, List<OrderCourseDTO>> map = new HashMap<>(coupons.size()); for (Coupon coupon : coupons) { // 1.找出优惠券的可用的课程 List<OrderCourseDTO> availableCourses = courses; if (coupon.getSpecific()) { // 1.1.限定了范围，查询券的可用范围 List<CouponScope> scopes = scopeService.lambdaQuery().eq(CouponScope::getCouponId, coupon.getId()).list(); // 1.2.获取范围对应的分类id Set<Long> scopeIds = scopes.stream().map(CouponScope::getBizId).collect(Collectors._toSet_()); // 1.3.筛选课程 availableCourses = courses.stream() .filter(c -> scopeIds.contains(c.getCateId())).collect(Collectors._toList_()); } if (CollUtils._isEmpty_(availableCourses)) { // 没有任何可用课程，抛弃 continue; } // 2.计算课程总价 int totalAmount = availableCourses.stream().mapToInt(OrderCourseDTO::getPrice).sum(); // 3.判断是否可用 Discount discount = DiscountStrategy._getDiscount_(coupon.getDiscountType()); if (discount.canUse(totalAmount, coupon)) { map.put(coupon, availableCourses); } } return map; } }

至此，天机学堂篇完结，能看到这里的你，已经超厉害了！！！

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