需求：通过查看当前商品ID，也要有展示当前商品可以使用的优惠券。用Feign组件，传产品ID，调用优惠券的Service

前提：微服务项目中数据库表设计尽量都是单表查询，商品表和优惠券表联系用第三个表来联系

商品表设计：

优惠券表：

联系表：

 优惠券的业务：

@Service
public class CouponServiceImpl implements CouponService {@ResourceCouponMapper couponMapper;@ResourceCouponProductRelationMapper productRelationMapper;@Overridepublic ResponseResult<List<CouponVo>> list(Long productId) {List<Coupon> couponList=new ArrayList<>();QueryWrapper<CouponProductRelation> relationQueryWrapper=new QueryWrapper<>();relationQueryWrapper.lambda().eq(CouponProductRelation::getProductId,productId);List<CouponProductRelation> relations = productRelationMapper.selectList(relationQueryWrapper);if (relations!=null&&relations.size()>0){for (CouponProductRelation c:relations) {QueryWrapper<Coupon>queryWrapper=new QueryWrapper<>();queryWrapper.lambda().eq(Coupon::getId,c.getCouponId());Coupon coupon = couponMapper.selectOne(queryWrapper);couponList.add(coupon);}}List<CouponVo> voList = CommonBeanUtils.copyListProperties(couponList, CouponVo::new);return   ResponseResult.success(voList) ;}
}

Feign调用：

@FeignClient(value = "cloud-coupon",path = "/coupon")
public interface CouponFeignApi {@GetMapping("/list")ResponseResult<List<CouponVo>> list(@RequestParam Long id);
}

消费者：

商品调用

@Service
public class ProductServiceImpl implements ProductService {@ResourceProductMapper productMapper;@ResourceProductSpecsMapper productSpecsMapper;@ResourceCouponFeignApi couponFeignApi;@Overridepublic ResponseResult<ProductVo> detail(Long productId) {Product product = productMapper.selectId(productId);ProductVo productVo = new ProductVo();BeanUtils.copyProperties(product, productVo);List<ProductSpecsVo> productVos = CommonBeanUtils.copyListProperties(productSpecsMapper.selectByProductId(productId), ProductSpecsVo::new);productVo.setProductSpecsList(productVos);ResponseResult<List<CouponVo>> list = couponFeignApi.list(productId);List<CouponVo> data = list.getData();productVo.setCouponVoList(data);return ResponseResult.success(productVo);}
}