详解Java如何在业务代码中优雅的使用策略模式

public static void main(String[] args) {
    PromotionActivity promotionActivity = null;
    String promotionKey = "COUPON";
    if(StringUtils.equals(promotionKey,"COUPON")){
        promotionActivity = new PromotionActivity(new CouponStrategy());
    }else if(StringUtils.equals(promotionKey,"CASHBACK")){
        promotionActivity = new PromotionActivity(new CashbackStrategy());
    }//......
    promotionActivity.execute();
}

public enum StrategyType {
    STRATEGY_A(1, "策略A"),
    STRATEGY_B(2, "策略B");
    private int code;
    private String desc;
    StrategyType(int code, String desc) {
        this.code = code;
        this.desc = desc;
    }
    public int getCode() {
        return code;
    }
    public String getDesc() {
        return desc;
    }
}

public interface Strategy {
    void execute();
    StrategyType getType();
}

@Component("strategyA")
public class StrategyA implements Strategy {
    @Override
    public void execute() {
        System.out.println("Executing strategy A");
    }
    @Override
    public StrategyType getType() {
        return StrategyType.STRATEGY_A;
    }
}

@Component("strategyB")
public class StrategyB implements Strategy {
    @Override
    public void execute() {
        System.out.println("Executing strategy B");
    }
    @Override
    public StrategyType getType() {
        return StrategyType.STRATEGY_B;
    }
}

@Service
public class StrategyFactory {
    private Map<StrategyType, Strategy> strategyMap = new ConcurrentHashMap<>();
    @Resource
    private List<Strategy> strategyList;
    public void execute(StrategyType type) {
        strategyMap.get(type).execute();
    }
    @PostConstruct
    public void init() {
        for (Strategy strategy : strategyList) {
            strategyMap.put(strategy.getType(), strategy);
        }
    }
}

@Service
public class StrategyService {
    @Resource
    private StrategyFactory strategyFactory;
    public void executeStrategy(StrategyType type) {
        strategyFactory.execute(type);
    }
}