DDD：订单管理 之 如何组织代码

背景

系统开发最难的是职责的合理分配，或者叫：“如何合理的组织代码”，今天说一个关于这方面问题的示例，希望大家多批评。

示例背景

参考数据字典

需求

OrderCode必须唯一。

Total = Sum（Subtotal）。

订单有三种状态：【未提交】、【待审核】和【已审核】，合理的状态迁移有：【未提交】----》【待审核】和【待审核】----》【已审核】，只有处于【未提交】状态的订单能修改。

订单和订单项中的状态必须合法，规则自己定义。

示例实现

项目结构

Application：应用层，负责领域逻辑的封装。主要角色：ApplicationService、CommandHandler。

Boostrap：启动管理层，负责启动过程管理，如：注册Ioc、初始化配置。主要角色：BootstrapListener。

Commands：命令层，是一个契约层。主要角色：Comamnd、DTO。

Controllers：控制器层，边界层。主要角色：Controller。

Domain：领域层，负责领域逻辑的组织。主要角色：Aggregate、Entity、ValueObject、Factory、DomainService、IRepository、IUnitOfWork。

Events：事件层，是一个契约层，跨聚合流程可以采用。主要角色：Event。

EventSubscribers：事件监听层。主要角色：EventSubscriber。

Infrastructure：基础设施层。主要角色：Repository、QueryService、UnitOfWork。

Query：查询层，为UI的查询提供服务，主要角色：QueryService。

项目整体采用简单的CQRS架构，Command端采用DDD组织，Query直接从数据库返回dynamic类型。Event可以用来处理跨聚合通信，也可以用来处理长事务或离线事务。

重点介绍的领域层

采用状态模式处理状态迁移。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Happy.Example.Domain.TestOrders
{
public interface ITestOrderState
{
void AddTestOrderDetail(TestOrderDetail testOrderDetail);

void UpdateTestOrderDetail(Guid testOrderDetailId, decimal subtotal);

void RemoveTestOrderDetail(Guid testOrderDetailId);

void Commit();

void Verify();

string Status { get; }

TestOrder TestOrder { set; }
}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Happy.Example.Domain.TestOrders
{
public partial class TestOrder
{
private abstract class TestOrderState : ITestOrderState
{
public virtual void AddTestOrderDetail(TestOrderDetail testOrderDetail)
{
this.ThrowInvalidOperationException();
}

public virtual void UpdateTestOrderDetail(Guid testOrderDetailId, decimal subtotal)
{
this.ThrowInvalidOperationException();
}

public virtual void RemoveTestOrderDetail(Guid testOrderDetailId)
{
this.ThrowInvalidOperationException();
}

public virtual void Commit()
{
this.ThrowInvalidOperationException();
}

public virtual void Verify()
{
this.ThrowInvalidOperationException();
}

public abstract string Status { get; }

public TestOrder TestOrder { protected get; set; }

private void ThrowInvalidOperationException()
{
throw new InvalidOperationException(string.Format("处于【{0}】的订单不能执行此操作！", this.Status));
}
}
}
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Happy.Example.Domain.TestOrders
{
public partial class TestOrder
{
private sealed class UnCommitted : TestOrderState
{
internal static readonly string UnCommittedStatus = "未提交";

public override void AddTestOrderDetail(TestOrderDetail testOrderDetail)
{
this.TestOrder.DoAddTestOrderDetail(testOrderDetail);
}

public override void UpdateTestOrderDetail(Guid testOrderDetailId, decimal subtotal)
{
this.TestOrder.DoUpdateTestOrderDetail(testOrderDetailId, subtotal);
}

public override void RemoveTestOrderDetail(Guid testOrderDetailId)
{
this.TestOrder.DoRemoveTestOrderDetail(testOrderDetailId);
}

public override void Commit()
{
this.TestOrder.DoCommit();
}

public override string Status
{
get { return UnCommittedStatus; }
}
}
}
}

采用封装集合手法处理Total的同步问题。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using Happy.Domain;
using Happy.Domain.Tree;
using Happy.Infrastructure.ExtentionMethods;
using Happy.Example.Events.TestOrders;

namespace Happy.Example.Domain.TestOrders
{
public partial class TestOrder : AggregateRoot<Guid>
{
private ITestOrderState _orderState;

protected TestOrder() { }

public TestOrder(string orderCode, string customer)
{
orderCode.MustNotNullAndNotWhiteSpace("orderCode");
customer.MustNotNullAndNotWhiteSpace("customer");

this.Id = Guid.NewGuid();
this.OrderCode = orderCode;
this.Customer = customer;
this.OrderState = TestOrderStateFactory.CreateUnCommittedTestOrderState(this);
this.TestOrderDetails = new List<TestOrderDetail>();
}

public virtual System.String OrderCode { get; protected set; }
public virtual System.String Customer { get; protected set; }
public virtual System.Decimal Total { get; protected set; }
public virtual System.String Status { get; protected set; }
public virtual ICollection<TestOrderDetail> TestOrderDetails { get; protected set; }

private ITestOrderState OrderState
{
get
{
if (_orderState == null)
{
_orderState = TestOrderStateFactory.Create(this, this.Status);
}

return _orderState;
}
set
{
_orderState = value;
this.Status = value.Status;
}
}

public void AddTestOrderDetail(TestOrderDetail testOrderDetail)
{
this.OrderState.AddTestOrderDetail(testOrderDetail);
}

public void UpdateTestOrderDetail(Guid testOrderDetailId, decimal subtotal)
{
this.OrderState.UpdateTestOrderDetail(testOrderDetailId, subtotal);
}

public void RemoveTestOrderDetail(Guid testOrderDetailId)
{
this.OrderState.RemoveTestOrderDetail(testOrderDetailId);
}

public void Commit()
{
this.OrderState.Commit();
}

public void Verify()
{
this.OrderState.Verify();
}

private void DoAddTestOrderDetail(TestOrderDetail testOrderDetail)
{
this.TestOrderDetails.Add(testOrderDetail);

this.Total += testOrderDetail.Subtotal;
}

private void DoUpdateTestOrderDetail(Guid testOrderDetailId, decimal subtotal)
{
var testOrderDetail = this.TestOrderDetails.First(x => x.Id == testOrderDetailId);

this.Total -= testOrderDetail.Subtotal;
testOrderDetail.Subtotal = subtotal;
this.Total += testOrderDetail.Subtotal;
}

private void DoRemoveTestOrderDetail(Guid testOrderDetailId)
{
var testOrderDetail = this.TestOrderDetails.First(x => x.Id == testOrderDetailId);

this.TestOrderDetails.Remove(testOrderDetail);
this.Total -= testOrderDetail.Subtotal;
}

private void DoCommit()
{
this.OrderState = TestOrderStateFactory.CreatePendingVerificationTestOrderState(this);
}

private void DoVerify()
{
this.OrderState = TestOrderStateFactory.CreateVerifiedTestOrderState(this);

this.PublishEvent(new TestOrderVerified());
}
}
}

效果图

背景

写这个简单的Demo过程，遇到了很多小的决策，这篇文章就看做一个开头吧，后边重点介绍每个决策点，在一篇文章中真的很难说完，喜欢看代码的朋友，先去https://happy.codeplex.com/下载。