订单管理系统底层设计：数据模型与状态机逻辑实战

-- 订单主表
CREATE TABLE orders (
  order_id VARCHAR(32) PRIMARY KEY,
  user_id BIGINT NOT NULL,
  order_status SMALLINT NOT NULL,
  total_amount DECIMAL(18,2) NOT NULL,
  create_time DATETIME NOT NULL,
  update_time DATETIME NOT NULL,
  -- 其他业务字段...
);

-- 订单商品明细表
CREATE TABLE order_items (
  item_id BIGINT PRIMARY KEY,
  order_id VARCHAR(32) NOT NULL,
  product_id BIGINT NOT NULL,
  quantity INT NOT NULL,
  unit_price DECIMAL(18,2) NOT NULL,
  -- 其他业务字段...
  FOREIGN KEY (order_id) REFERENCES orders(order_id)
);

-- 订单状态变更日志表
CREATE TABLE order_status_log (
  log_id BIGINT PRIMARY KEY,
  order_id VARCHAR(32) NOT NULL,
  from_status SMALLINT NOT NULL,
  to_status SMALLINT NOT NULL,
  operator VARCHAR(64),
  operate_time DATETIME NOT NULL,
  remark VARCHAR(255),
  FOREIGN KEY (order_id) REFERENCES orders(order_id)
);

public enum OrderStatus
{
    PendingPayment = 1,    // 待支付
    Paid = 2,              // 已支付
    Processing = 3,        // 处理中
    Shipped = 4,           // 已发货
    Completed = 5,         // 已完成
    Cancelled = 6,         // 已取消
    Refunded = 7           // 已退款
}

public class OrderStateMachine
{
    private static readonly Dictionary<OrderStatus, List<OrderStatus>> _transitions = new()
    {
        [OrderStatus.PendingPayment] = new() { OrderStatus.Paid, OrderStatus.Cancelled },
        [OrderStatus.Paid] = new() { OrderStatus.Processing, OrderStatus.Refunded },
        [OrderStatus.Processing] = new() { OrderStatus.Shipped, OrderStatus.Cancelled },
        [OrderStatus.Shipped] = new() { OrderStatus.Completed, OrderStatus.Refunded },
        // 其他状态转移规则...
    };

    public bool CanTransition(OrderStatus from, OrderStatus to)
    {
        return _transitions.ContainsKey(from) && 
               _transitions[from].Contains(to);
    }
}

public class OrderService
{
    public async Task<Order> CreateOrderAsync(OrderCreateRequest request)
    {
        // 验证业务规则
        if (!await ValidateOrderItems(request.Items))
            throw new BusinessException("商品信息不合法");
        
        // 生成订单号
        var orderId = GenerateOrderId();
        
        // 开启事务
        using var transaction = _dbContext.Database.BeginTransaction();
        
        try
        {
            // 创建订单主记录
            var order = new Order
            {
                OrderId = orderId,
                UserId = request.UserId,
                OrderStatus = (int)OrderStatus.PendingPayment,
                TotalAmount = CalculateTotal(request.Items),
                CreateTime = DateTime.Now,
                UpdateTime = DateTime.Now
            };
            
            _dbContext.Orders.Add(order);
            
            // 添加订单商品
            foreach (var item in request.Items)
            {
                _dbContext.OrderItems.Add(new OrderItem
                {
                    OrderId = orderId,
                    ProductId = item.ProductId,
                    Quantity = item.Quantity,
                    UnitPrice = item.UnitPrice
                });
            }
            
            // 记录状态变更
            _dbContext.OrderStatusLogs.Add(new OrderStatusLog
            {
                OrderId = orderId,
                FromStatus = 0,
                ToStatus = (int)OrderStatus.PendingPayment,
                OperateTime = DateTime.Now,
                Operator = "system"
            });
            
            await _dbContext.SaveChangesAsync();
            await transaction.CommitAsync();
            
            return order;
        }
        catch
        {
            await transaction.RollbackAsync();
            throw;
        }
    }
}

public async Task ChangeOrderStatusAsync(string orderId, OrderStatus newStatus, string operator)
{
    var order = await _dbContext.Orders.FindAsync(orderId);
    if (order == null)
        throw new NotFoundException("订单不存在");
    
    var currentStatus = (OrderStatus)order.OrderStatus;
    
    // 验证状态转移是否合法
    if (!_stateMachine.CanTransition(currentStatus, newStatus))
        throw new BusinessException("不允许的状态变更");
    
    // 执行状态变更
    order.OrderStatus = (int)newStatus;
    order.UpdateTime = DateTime.Now;
    
    // 记录状态变更日志
    _dbContext.OrderStatusLogs.Add(new OrderStatusLog
    {
        OrderId = orderId,
        FromStatus = (int)currentStatus,
        ToStatus = (int)newStatus,
        OperateTime = DateTime.Now,
        Operator = operator
    });
    
    await _dbContext.SaveChangesAsync();
    
    // 触发后续业务逻辑
    await _eventBus.PublishAsync(new OrderStatusChangedEvent
    {
        OrderId = orderId,
        FromStatus = currentStatus,
        ToStatus = newStatus
    });
}