我利用Spring 类优化了一下 #2

public interface AbstractOrderHandler {
    String handle(OrderDTO dto);
    String type();
}

@Component
public class LitbHandler implements AbstractHandler {

    @Override
    public String handle(OrderDTO dto) {
        return OrderType.litb.toString();
    }

    @Override
    public String type() {
        return OrderType.litb.toString();
    }
}

@Service
public class OrderServiceImpl implements OrderService {

    @Resource
    public ApplicationContext applicationContext;

    @Override
    public String handle(OrderDTO dto) {
        String orderType = String.valueOf(dto.getType());

        // Spring 有个 Map Cache 根据 class 来缓存 bean Name, 此处无需担忧性能
        Map<String, AbstractOrderHandler> beans = applicationContext.getBeansOfType(AbstractOrderHandler.class);
        beans.values().stream()
                .filter(x -> x.type().equals(orderType))
                .findFirst()
                .orElseThrow(() -> new RuntimeException("not found handler for type: " + orderType))
                .handle(dto);

        return null;
    }
}