SpringBoot中优化if-else语句的七种方法

public interface PaymentStrategy {
    void pay(double amount);
}

// 微信支付
@Component
public class WeiXinPayment implements PaymentStrategy {
    public void pay(double amount) {
        // 实现微信支付逻辑
    }
}

// 其他支付方式的实现...

@Service
public class PaymentService {
    private final Map<String, PaymentStrategy> strategies;

    @Autowired
    public PaymentService(List<PaymentStrategy> paymentStrategies) {
        this.strategies = paymentStrategies.stream()
                .collect(Collectors.toMap(s -> s.getClass().getSimpleName().toLowerCase(), Function.identity()));
    }

    public void processPayment(String strategyName, double amount) {
        PaymentStrategy strategy = strategies.getOrDefault(strategyName, null);
        if (strategy != null) {
            strategy.pay(amount);
        } else {
            throw new IllegalArgumentException("Unsupported payment strategy: " + strategyName);
        }
    }
}

public enum OrderStatus {
    NEW {
        @Override
        public void process() {
            // 处理新建订单
        }
    },
    // 已支付
    PAID {
    @Override
    public void process() {
      // TODO
    }
  };
    // 其他状态...
    ;

    public abstract void process();
}

@Service
public class OrderService {
    public void handleOrder(OrderStatus status) {
        status.process();
    }
}

public interface Notification {
    void send(String message);
}

@Component
public class EmailNotification implements Notification {
    // 实现发送邮件的逻辑
}
@Component
public class SmsNotification implements Notification {
    // 实现发送邮件的逻辑
}
// 其他通知方式的实现...

@Service
public class NotificationService {
    @Autowired
    private List<Notification> notifications;

    public void notifyAll(String message) {
        notifications.forEach(notification -> notification.send(message));
    }
}

@Service
public class DiscountService {
    private final Map<String, Function<Double, Double>> discountFunctions = new HashMap<>();

    public DiscountService() {
        discountFunctions.put("VIP1", price -> price * 0.95);
        discountFunctions.put("VIP2", price -> price * 0.95 - 20 );
        // 其他VIP等级的折扣设置...
    }

    public double applyDiscount(String discountCode, double price) {
        return discountFunctions.getOrDefault(discountCode, Function.identity()).apply(price);
    }
}

public interface OrderState {
    void pay(OrderContext orderContext);
    void ship(OrderContext orderContext);
    void complete(OrderContext orderContext);
}

public class UnpaidState implements OrderState {  
    private OrderContext context;  
  
    public UnpaidState(OrderContext context) {  
        this.context = context;  
    }  
  
    @Override  
    public void pay(OrderContext orderContext) {  
        // 更新订单状态为已支付  
        orderContext.setState(new PaidState(orderContext));  
        // 执行支付逻辑  
        System.out.println("Order paid successfully");  
    }  
  
    @Override  
    public void ship(OrderContext orderContext) {  
        throw new IllegalStateException("Cannot ship an unpaid order");  
    }  
  
    @Override  
    public void complete(OrderContext orderContext) {  
        throw new IllegalStateException("Cannot complete an unpaid order");  
    }  
}  
  
// 你可以定义 PaidState, ShippedState, CompletedState 等类

public class OrderContext {  
    private OrderState state;  
  
    public OrderContext(OrderState state) {  
        this.state = state;  
    }  
  
    public void setState(OrderState state) {  
        this.state = state;  
    }  
  
    public void pay() {  
        state.pay(this);  
    }  
  
    public void ship() {  
        state.ship(this);  
    }  
  
    public void complete() {  
        state.complete(this);  
    }  
  
    // 其他订单属性和方法...  
}

public class Client {  
    public static void main(String[] args) {  
        OrderContext order = new OrderContext(new UnpaidState(order));  
  
        // 尝试支付订单  
        order.pay();  
  
        // 尝试发货（根据订单状态，这可能会抛出异常）  
        // order.ship();  
  
        // 假设订单支付后，订单状态已更新为 PaidState  
        // order.setState(new PaidState(order));  
        // order.ship();  
    }  
}