Java订单管理系统流程与状态设计解析

public enum OrderStatus {
    CREATED, PAID, SHIPPED, DELIVERED, CANCELLED;

    // 可扩展：定义哪些状态能转向哪些状态
    public boolean canTransitionTo(OrderStatus next) {
        return switch (this) {
            case CREATED -> next == PAID || next == CANCELLED;
            case PAID -> next == SHIPPED || next == CANCELLED;
            case SHIPPED -> next == DELIVERED || next == CANCELLED;
            case DELIVERED, CANCELLED -> false;
        };
    }
}

public class Order {
    private Long id;
    private OrderStatus status = OrderStatus.CREATED;
    private BigDecimal amount;
    private LocalDateTime createTime;

    public void pay() {
        if (status.canTransitionTo(OrderStatus.PAID)) {
            this.status = OrderStatus.PAID;
            this.payTime = LocalDateTime.now();
        } else {
            throw new IllegalStateException("Cannot pay from " + status);
        }
    }

    public void ship() {
        if (status.canTransitionTo(OrderStatus.SHIPPED)) {
            this.status = OrderStatus.SHIPPED;
            this.shipTime = LocalDateTime.now();
        }
    }
    // 其他状态方法...
}

// 初始化状态分组容器
Map> statusIndex = new EnumMap(OrderStatus.class);
Arrays.stream(OrderStatus.values()).forEach(s -> statusIndex.put(s, new ArrayList()));

// 创建新订单
Order order = new Order(1001L, BigDecimal.valueOf(299.00));
statusIndex.get(OrderStatus.CREATED).add(order);

// 支付 → 状态自动校验并更新
order.pay();
statusIndex.get(OrderStatus.CREATED).remove(order);
statusIndex.get(OrderStatus.PAID).add(order);

// 发货
order.ship();
statusIndex.get(OrderStatus.PAID).remove(order);
statusIndex.get(OrderStatus.SHIPPED).add(order);