策略模式 - 实现优惠券

这次比较简单粗暴哈，先按照下图来创建相对应的类和方法吧。

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截屏2022-07-08 上午11.24.20.png

CouponStrategyContext.java

@Data
@AllArgsConstructor
@Component
@Slf4j
public class CouponStrategyContext implements ApplicationContextAware {

    /**
     * 优惠券策略类集合
     */
    private static Map<String, CouponStrategy> couponStrategyMap;


    /**
     * 策略上下文对象委派具体的策略执行算法
     *
     * @param couponDTO
     * @return
     */
    public static Object couponHandler(CouponDTO couponDTO) {
        return getCouponStrategy(couponDTO.getCouponTypeEnum()).couponHandler(couponDTO);
    }

    /**
     * 获取适用的策略处理类
     *
     * @param couponType
     * @return
     */
    private static CouponStrategy getCouponStrategy(CouponTypeEnum couponType) {
        return Optional.ofNullable(couponStrategyMap.get(couponType.name()))
                .orElseThrow(() -> new RuntimeException(String.format("not found coupon type strategy , coupon type is %s", couponType.name())));
    }

    /**
     * 从容器中加载所有优惠券策略接口的实现类，注册到优惠券策略集合中
     *
     * @param applicationContext
     * @throws BeansException
     */
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        Map<String, CouponStrategy> strategyBeans = applicationContext.getBeansOfType(CouponStrategy.class);
        if (strategyBeans == null || strategyBeans.size() == 0) {
            // 无可用的优惠券策略
            log.info("无可用的优惠券策略");
            return;
        }
        log.info("预加载优惠策略集合Map,一共有"+strategyBeans.size()+"策略");
        couponStrategyMap = new HashMap<>(strategyBeans.size());
        for (CouponStrategy strategy : strategyBeans.values()) {
            couponStrategyMap.put(strategy.applyCouponType().name(), strategy);
            log.info("register strategy " + strategy.applyCouponType());
        }
        log.info("加载完毕 - couponStrategyMap{}",couponStrategyMap);
    }
}

CouponStrategyContext是唯一一个有代码的哈，可以自行参考具体的实现哈。

最后测试一下

        CouponDTO couponDTO = new CouponDTO();
        couponDTO.setCouponTypeEnum(CouponTypeEnum.DiscountCoupon);
        Object o = CouponStrategyContext.couponHandler(couponDTO);