小议传统分层与新式分层，抑或与DDD分层

技术2022-07-02 187

引言

本文提到的分层只是软件架构上的分层。文中的传统分层指的是传统的三层结构：UI（界面表现层）,BLL（业务逻辑层）,DAL（数据访问层）。文中提出的观点也都是个人的一点认识，与任何组织没有关系，如有异议，还请各位踊跃拍砖。

当然了，出现的这些问题，也可能只是我个人的问题，不代表每个人都存在。无则加勉，有则改正吧。如果是个人的问题，那就当是个人总结吧，大家看看就算了。

这里说到的传统分层，也有可能是我对于分层的错误理解造成的，但是我看见的不只是我的项目是这么的结构，很多的项目也都是这样的结构。里面的代码，都和我理解的一样，至少可以说明，还是有一部分人犯了和我一样的错误。

传统分层

传统分层最大的问题就在于割裂了上层与下层之间的联系，把他们之间的关系变成了简单的接口调用，变成了完全的接口形式主义。同时，忽略了下层是为上层提供服务的，不是单独存在的，下层提供的服务应该受到上层的规约。当然，也不是说不可以提供更多的服务，但是至少应该提供上层需要的，然后再考虑提供一些“边角料”。

我们先看一个传统分层的解决方案结构。

相互之间的引用关系是：UI引用BLL、Entity、Common；BLL引用IDAL、Entity、Common；IDAL引用Entity；DAL引用IDAL、Entity、Common。

UI Code private void button1_Click(object sender, EventArgs e) { _02_BLL.OrderBll orderBll = Common.ServiceLocator.LoadService<_02_BLL.OrderBll>(); orderBll.SubmitOrder(new _05_Entity.OrderEntity() { OrderSeqNo = "123", OrderAmount = 1000 }); } .src_container{background-color:#e7e5dc; width:99%; overflow:hidden; margin:12px 0 12px 0 !important; padding:0px 3px 3px 0px} .src_container .titlebar{ background-color:#d4dfff; border:1px solid #4f81bd; border-bottom:0; padding:3px 24px; margin:0; width:auto; line-height:120%; overflow:hidden; text-align:left; font-size:12px} .src_container .toolbar{ display:inline; font-weight:normal; font-size:100%; float:right; cursor:hand; color:#00f; text-align:left; overflow:hidden} .toolbar span.button{ display:inline; font-weight:normal; font-size:100%; cursor:hand; color:#00f; text-align:left; overflow:hidden; cursor:pointer;} .src_container div.clientarea{ background-color:white; border:1px solid #4f81bd; margin:0; width:auto !important; width:100%; height:auto; overflow:auto; text-align:left; font-size:12px; font-family: "Courier New","Consolas","Fixedsys",courier,monospace,serif} .src_container ol.mainarea{ padding:0 0 0 52px; margin:0; background-color:#f7f7ff !important} .number_show{ padding-left:52px !important; list-style:decimal outside !important} .number_show li{ list-style:decimal outside !important; border-left:1px dotted #4f81bd} .number_hide{ padding-left:0px !important; list-style-type:none !important} .number_hide li{ list-style-type:none !important; border-left:0px} ol.mainarea li{ display:list-item !important; font-size:12px !important; margin:0 !important; line-height:18px !important; padding:0 0 0 0px !important; background-color:#f7f7ff !important; color:#4f81bd} ol.mainarea li pre{color:black; line-height:18px; padding:0 0 0 12px !important; margin:0em; background-color:#fff !important} .linewrap ol.mainarea li pre{white-space:pre-wrap; white-space:-moz-pre-wrapwhite-space:-pre-wrap; white-space:-o-pre-wrap; word-wrap:break-word} ol.mainarea li pre.alt{ background-color:#f7f7ff !important} <script language="javascript"> function CopyCode(key){var codeElement=null;var trElements=document.all.tags("ol");var i;for(i=0;i BLL Code public class OrderBll { IOrderDal _orderDal; public OrderBll() { _orderDal = Common.ServiceLocator.LoadService<_03_IDAL.IOrderDal>(); } public bool SubmitOrder(OrderEntity order) { return _orderDal.Add(order); } } .src_container{background-color:#e7e5dc; width:99%; overflow:hidden; margin:12px 0 12px 0 !important; padding:0px 3px 3px 0px} .src_container .titlebar{ background-color:#d4dfff; border:1px solid #4f81bd; border-bottom:0; padding:3px 24px; margin:0; width:auto; line-height:120%; overflow:hidden; text-align:left; font-size:12px} .src_container .toolbar{ display:inline; font-weight:normal; font-size:100%; float:right; cursor:hand; color:#00f; text-align:left; overflow:hidden} .toolbar span.button{ display:inline; font-weight:normal; font-size:100%; cursor:hand; color:#00f; text-align:left; overflow:hidden; cursor:pointer;} .src_container div.clientarea{ background-color:white; border:1px solid #4f81bd; margin:0; width:auto !important; width:100%; height:auto; overflow:auto; text-align:left; font-size:12px; font-family: "Courier New","Consolas","Fixedsys",courier,monospace,serif} .src_container ol.mainarea{ padding:0 0 0 52px; margin:0; background-color:#f7f7ff !important} .number_show{ padding-left:52px !important; list-style:decimal outside !important} .number_show li{ list-style:decimal outside !important; border-left:1px dotted #4f81bd} .number_hide{ padding-left:0px !important; list-style-type:none !important} .number_hide li{ list-style-type:none !important; border-left:0px} ol.mainarea li{ display:list-item !important; font-size:12px !important; margin:0 !important; line-height:18px !important; padding:0 0 0 0px !important; background-color:#f7f7ff !important; color:#4f81bd} ol.mainarea li pre{color:black; line-height:18px; padding:0 0 0 12px !important; margin:0em; background-color:#fff !important} .linewrap ol.mainarea li pre{white-space:pre-wrap; white-space:-moz-pre-wrapwhite-space:-pre-wrap; white-space:-o-pre-wrap; word-wrap:break-word} ol.mainarea li pre.alt{ background-color:#f7f7ff !important} <script language="javascript"> function CopyCode(key){var codeElement=null;var trElements=document.all.tags("ol");var i;for(i=0;i

IDAL Code public interface IOrderDal { bool Add(OrderEntity order); } .src_container{background-color:#e7e5dc; width:99%; overflow:hidden; margin:12px 0 12px 0 !important; padding:0px 3px 3px 0px} .src_container .titlebar{ background-color:#d4dfff; border:1px solid #4f81bd; border-bottom:0; padding:3px 24px; margin:0; width:auto; line-height:120%; overflow:hidden; text-align:left; font-size:12px} .src_container .toolbar{ display:inline; font-weight:normal; font-size:100%; float:right; cursor:hand; color:#00f; text-align:left; overflow:hidden} .toolbar span.button{ display:inline; font-weight:normal; font-size:100%; cursor:hand; color:#00f; text-align:left; overflow:hidden; cursor:pointer;} .src_container div.clientarea{ background-color:white; border:1px solid #4f81bd; margin:0; width:auto !important; width:100%; height:auto; overflow:auto; text-align:left; font-size:12px; font-family: "Courier New","Consolas","Fixedsys",courier,monospace,serif} .src_container ol.mainarea{ padding:0 0 0 52px; margin:0; background-color:#f7f7ff !important} .number_show{ padding-left:52px !important; list-style:decimal outside !important} .number_show li{ list-style:decimal outside !important; border-left:1px dotted #4f81bd} .number_hide{ padding-left:0px !important; list-style-type:none !important} .number_hide li{ list-style-type:none !important; border-left:0px} ol.mainarea li{ display:list-item !important; font-size:12px !important; margin:0 !important; line-height:18px !important; padding:0 0 0 0px !important; background-color:#f7f7ff !important; color:#4f81bd} ol.mainarea li pre{color:black; line-height:18px; padding:0 0 0 12px !important; margin:0em; background-color:#fff !important} .linewrap ol.mainarea li pre{white-space:pre-wrap; white-space:-moz-pre-wrapwhite-space:-pre-wrap; white-space:-o-pre-wrap; word-wrap:break-word} ol.mainarea li pre.alt{ background-color:#f7f7ff !important} <script language="javascript"> function CopyCode(key){var codeElement=null;var trElements=document.all.tags("ol");var i;for(i=0;i

DAL Code public class OrderDal:_03_IDAL.IOrderDal { public bool Add(_05_Entity.OrderEntity order) { IDbConnection conn = new SqlConnection(); conn.Open(); IDbCommand comm = conn.CreateCommand(); IDbDataParameter param = comm.CreateParameter(); param.Direction = ParameterDirection.Input; param.DbType = DbType.String; param.ParameterName = "OrderSeqNo"; if (comm.ExecuteNonQuery() > 0) return true; else return false; } } .src_container{background-color:#e7e5dc; width:99%; overflow:hidden; margin:12px 0 12px 0 !important; padding:0px 3px 3px 0px} .src_container .titlebar{ background-color:#d4dfff; border:1px solid #4f81bd; border-bottom:0; padding:3px 24px; margin:0; width:auto; line-height:120%; overflow:hidden; text-align:left; font-size:12px} .src_container .toolbar{ display:inline; font-weight:normal; font-size:100%; float:right; cursor:hand; color:#00f; text-align:left; overflow:hidden} .toolbar span.button{ display:inline; font-weight:normal; font-size:100%; cursor:hand; color:#00f; text-align:left; overflow:hidden; cursor:pointer;} .src_container div.clientarea{ background-color:white; border:1px solid #4f81bd; margin:0; width:auto !important; width:100%; height:auto; overflow:auto; text-align:left; font-size:12px; font-family: "Courier New","Consolas","Fixedsys",courier,monospace,serif} .src_container ol.mainarea{ padding:0 0 0 52px; margin:0; background-color:#f7f7ff !important} .number_show{ padding-left:52px !important; list-style:decimal outside !important} .number_show li{ list-style:decimal outside !important; border-left:1px dotted #4f81bd} .number_hide{ padding-left:0px !important; list-style-type:none !important} .number_hide li{ list-style-type:none !important; border-left:0px} ol.mainarea li{ display:list-item !important; font-size:12px !important; margin:0 !important; line-height:18px !important; padding:0 0 0 0px !important; background-color:#f7f7ff !important; color:#4f81bd} ol.mainarea li pre{color:black; line-height:18px; padding:0 0 0 12px !important; margin:0em; background-color:#fff !important} .linewrap ol.mainarea li pre{white-space:pre-wrap; white-space:-moz-pre-wrapwhite-space:-pre-wrap; white-space:-o-pre-wrap; word-wrap:break-word} ol.mainarea li pre.alt{ background-color:#f7f7ff !important} <script language="javascript"> function CopyCode(key){var codeElement=null;var trElements=document.all.tags("ol");var i;for(i=0;i Unity Container Locator using System.Configuration; using System.Globalization; using Microsoft.Practices.Unity; using Microsoft.Practices.Unity.Configuration; using Microsoft.Practices.Unity.InterceptionExtension; using System.Web; using System; namespace Common { public static class ServiceLocator { // private static readonly InterfaceInterceptor injector = new InterfaceInterceptor (); private static readonly TransparentProxyInterceptor injector = new TransparentProxyInterceptor(); public static IUnityContainer Container { get; private set; } static ServiceLocator() { Container = new UnityContainer(); UnityConfigurationSection unitySection = ConfigurationManager.GetSection("unity") as UnityConfigurationSection; if (unitySection == null) { throw new ConfigurationErrorsException(string.Format(CultureInfo.CurrentCulture, "missing unity configuration section")); } Container.AddNewExtension<Interception>(); unitySection.Configure(Container, "Container"); } /// /// 没?有D为a映3射?指?定¨别e名? /// name属?性?没?有D赋3值μ /// /// /// public static T LoadService () { Container.Configure<Interception>().SetDefaultInterceptorFor (injector); return Container.Resolve (); } /// /// 为a映3射?指?定¨别e名? /// name属?性?赋3值μ /// /// /// /// public static T LoadService ( string serviceName) { Container.Configure<Interception>().SetDefaultInterceptorFor (injector); return Container.Resolve (serviceName); } } } .src_container{background-color:#e7e5dc; width:99%; overflow:hidden; margin:12px 0 12px 0 !important; padding:0px 3px 3px 0px} .src_container .titlebar{ background-color:#d4dfff; border:1px solid #4f81bd; border-bottom:0; padding:3px 24px; margin:0; width:auto; line-height:120%; overflow:hidden; text-align:left; font-size:12px} .src_container .toolbar{ display:inline; font-weight:normal; font-size:100%; float:right; cursor:hand; color:#00f; text-align:left; overflow:hidden} .toolbar span.button{ display:inline; font-weight:normal; font-size:100%; cursor:hand; color:#00f; text-align:left; overflow:hidden; cursor:pointer;} .src_container div.clientarea{ background-color:white; border:1px solid #4f81bd; margin:0; width:auto !important; width:100%; height:auto; overflow:auto; text-align:left; font-size:12px; font-family: "Courier New","Consolas","Fixedsys",courier,monospace,serif} .src_container ol.mainarea{ padding:0 0 0 52px; margin:0; background-color:#f7f7ff !important} .number_show{ padding-left:52px !important; list-style:decimal outside !important} .number_show li{ list-style:decimal outside !important; border-left:1px dotted #4f81bd} .number_hide{ padding-left:0px !important; list-style-type:none !important} .number_hide li{ list-style-type:none !important; border-left:0px} ol.mainarea li{ display:list-item !important; font-size:12px !important; margin:0 !important; line-height:18px !important; padding:0 0 0 0px !important; background-color:#f7f7ff !important; color:#4f81bd} ol.mainarea li pre{color:black; line-height:18px; padding:0 0 0 12px !important; margin:0em; background-color:#fff !important} .linewrap ol.mainarea li pre{white-space:pre-wrap; white-space:-moz-pre-wrapwhite-space:-pre-wrap; white-space:-o-pre-wrap; word-wrap:break-word} ol.mainarea li pre.alt{ background-color:#f7f7ff !important} <script language="javascript"> function CopyCode(key){var codeElement=null;var trElements=document.all.tags("ol");var i;for(i=0;i

.src_container{background-color:#e7e5dc; width:99%; overflow:hidden; margin:12px 0 12px 0 !important; padding:0px 3px 3px 0px} .src_container .titlebar{ background-color:#d4dfff; border:1px solid #4f81bd; border-bottom:0; padding:3px 24px; margin:0; width:auto; line-height:120%; overflow:hidden; text-align:left; font-size:12px} .src_container .toolbar{ display:inline; font-weight:normal; font-size:100%; float:right; cursor:hand; color:#00f; text-align:left; overflow:hidden} .toolbar span.button{ display:inline; font-weight:normal; font-size:100%; cursor:hand; color:#00f; text-align:left; overflow:hidden; cursor:pointer;} .src_container div.clientarea{ background-color:white; border:1px solid #4f81bd; margin:0; width:auto !important; width:100%; height:auto; overflow:auto; text-align:left; font-size:12px; font-family: "Courier New","Consolas","Fixedsys",courier,monospace,serif} .src_container ol.mainarea{ padding:0 0 0 52px; margin:0; background-color:#f7f7ff !important} .number_show{ padding-left:52px !important; list-style:decimal outside !important} .number_show li{ list-style:decimal outside !important; border-left:1px dotted #4f81bd} .number_hide{ padding-left:0px !important; list-style-type:none !important} .number_hide li{ list-style-type:none !important; border-left:0px} ol.mainarea li{ display:list-item !important; font-size:12px !important; margin:0 !important; line-height:18px !important; padding:0 0 0 0px !important; background-color:#f7f7ff !important; color:#4f81bd} ol.mainarea li pre{color:black; line-height:18px; padding:0 0 0 12px !important; margin:0em; background-color:#fff !important} .linewrap ol.mainarea li pre{white-space:pre-wrap; white-space:-moz-pre-wrapwhite-space:-pre-wrap; white-space:-o-pre-wrap; word-wrap:break-word} ol.mainarea li pre.alt{ background-color:#f7f7ff !important}

上层在调用下层的时候，不是调用自己需要的，而是从下层提供的服务中筛选一些可以用的，凑合用一下。如果发现没有自己可以用的，就在IDAL文件中添加一个，然后在DAL文件中实现以下，这下好了，BLL可以用了。这样也会造成在开发DAL层的时候，没有充分考虑BLL的需要，自己盲目实现一些，然后BLL用的时候，才发现很多还要重新写。造成大量的浪费，代码、人力、时间、精力都浪费一部分了。也会影响到开发的进度。

新式分层,抑或叫做DDD分层

说是新式分层，其实也是我随便叫的。就是这段时间看了博客园的一些DDD文章，还有就是codeplex上的两个项目NLayerApp和SmartCA的源码。看了这些之后，有的一点理解。不管是神似还是形似吧，反正觉得比以前传统分层有一点道理，就分享出来了，也挣点人气，骗点点击量，哈哈。

先来一张图吧。

DDD中的分层主要是四层：Presentation（表现层），Application（应用层），Domain（领域层），Infrastructure（基础层）。

Presentation相当于以前的UI层。Application是一个任务的调度层，没有实际的业务逻辑，也不推荐放入业务逻辑，实际中可以用Wcf来代替，或者使用普通的类库就可以。其实就是根据UI的业务调用，然后映射到具体的领域对象身上去。也可以通过Application来暴露粗粒度的业务处理，因为领域层的业务处理是细粒度的。没有了以前的DAL，把它的部分放入了Infrastructure层。

以前的IDAL被放入了Domain，在图上，是Domain.Core项目，这个项目会被Infrastructure引用。因为Domain.Core中的IDAL相当于是领域对象对于持久化提出的要求，也就是说必须要实现这些功能，这些都是领域对象需要的。具体的如何实现，具体如何持久化，是持久化到关系数据库还是文件系统，还是内存数据库，都由具体的实现来定义。也就是图中的Infrastructure.Data.Core和Infrastructure.Data.MainModule项目。这两个项目中的实现，实现的都是领域对象持久化所需要的，不会实现一大丢不必要的方法。不知道这算不算是改进呢？

结论

传统分层，或者说是我理解的传统分层，存在的问题就是割裂层之间的联系，形式化了层之间的联系。没有表达出上层对于下层的需要，下层是为上层服务的，这些联系。DDD的分层可以解决这个问题，会提高开发的效率，少走一些弯路。

不知道大家是如何认识的呢？？？？？？？？期待大家的回复，拍砖。

Technorati 标签: DDD, NLayer, 分层

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