《模式——工程化实现及扩展》（设计模式C# 版）《中介者模式》——“自我检验" 参考答案

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设计模式 C#C C++配置管理

转自：《模式——工程化实现及扩展》（设计模式C# 版）

http://www.cnblogs.com/callwangxiang/

MarvellousWorks公司有 A、 B、 C三个部门负责文件的拟稿、审批和备案，现有的流程如下：

1. A部门拟稿后将文件报 B部门审核

2. B部门对于文件审核后，确认文件体例没有缺项后就通知 C部门发布

3. 如果 B部门发现文件体例有缺项时，将文件返回给 A部门重新修改

4. C部门在接到 B部门传来的文件时，先再发布，然后对其归档

不过， MarvellousWorks的管理层为了加强部门间文件流转的管理，正在酝酿修改工作流程：

1、增加 D部门专门负责归档， C部门将归档职责划入 D部门后只负责发布文件

2、 C部门发布文件后也须先在 D部门归档

3、 A、 B部门间所有往复流转的中间文件也都报给 D部门归档

请采用本章介绍的中介者模式及其扩展处理，将文件的流转调度过程从 A、 B、 C、 D各对象的职责中独立出来，并用单元测试验证不同的流转过程。

文件对象的定义

class Document
{
     #region essential fields
     public string Subject { get ; set ; }
     public string Body { get ; set ; }
     #endregion

     #region optional fields
     public string Comment { get ; set ; }
     #endregion

     public override string ToString()
    {
         return string .Format( " \n[{0}]\n------------------\n{1}\n({2})\n " , Subject, Body, Comment);
    }
}

参考答案

分析第一步

上述A、B、C、D部门间的协作关系比较复杂，而且预期很快会变化，但协作的中间内容很简单——都是文件，所以采用事件方式，由.NET Framework自己的事件机制作为中介者相对很简单，而且类型间的依赖关系全都推给.NET Framework，为以后扩展更多参与方的协作关系提供便利。

据此，我们定义A、B、C、D时全部采用事件作为提供给外中介者协调响应关系的入口。

增加如下类型

class DocumentEventArgs : EventArgs
{
    Document document;
     public DocumentEventArgs(Document document)
    {
         this .document = document;
    }
     public Document Document{ get { return document;}}
}

abstract class Department
{
     protected Document document = new Document();
     public Document Document
    {
         get { return document;}
         protected set { document = value;}
    }
}

分析第二步

如果直接通过事件重载操作符 += 和-=建立各Colleague的响应关系，需要重复编写代码，而且不能在系统上线后将这个工作交给管理员维护。

因此，考虑参考前面的Builder模式，增加一个基于配置动态维护维护事件响应关系的对象。

实现和单元测试验证

1、验证“分析第一步”的设想

/// <summary>
/// 测试手工定义事件中介者的交互关系
/// </summary>
[TestMethod]
public void TestManualDefineEventMediatorInSucceedBranch()
{
     //   用事件配置松散的响应关系
    a1.WriteDocumentFinishedHandler += b1.OnReceiveFileToReview;
    b1.ReviewDocumentFailedHandler += a1.OnReviewFailed;
    b1.ReviewDocumentSucceedHandler += c1.OnReceiveFileToPublish;
    b1.ReviewDocumentSucceedHandler += c1.OnReceiveFileToArchive;

     //   成功的路径
    a1.Write( " a " , " b " , " c " );

     //   验证修订后的内容曾经流转给了B
    Assert.AreEqual < string > ( " a " , b1.Document.Subject);
    Assert.AreEqual < string > ( " b " , b1.Document.Body);
    Assert.AreEqual < string > ( " c " , b1.Document.Comment);

     //   验证修订后的内容也曾经流转给了C
    Assert.AreEqual < string > ( " a " , c1.Document.Subject);
    Assert.AreEqual < string > ( " b " , c1.Document.Body);
    Assert.AreEqual < string > ( " c " , c1.Document.Comment);
}

Output窗口

------ Test started: Assembly: Mediator . Tests . dll ------

A begin write
A write finished

[a]
------------------
b
( c )

B received doc from A to review
B begin review
B review succeed
C received doc to publish from B
C published
C received doc to archive from B
C archived

1 passed , 0 failed , 0 skipped , took 0.50 seconds ( MSTest 10.0 ).

/// <summary>
/// 测试手工定义事件中介者的交互关系
/// </summary>
[TestMethod]
public void TestManualDefineEventMediatorInFailedBranch()
{
     //   用事件配置松散的响应关系
    a1.WriteDocumentFinishedHandler += b1.OnReceiveFileToReview;
    b1.ReviewDocumentFailedHandler += a1.OnReviewFailed;
    b1.ReviewDocumentSucceedHandler += c1.OnReceiveFileToPublish;
    b1.ReviewDocumentSucceedHandler += c1.OnReceiveFileToArchive;

     //   失败的路径
    a1.Write( " a " , "" , "" );

     //   验证确实文档曾经流转给了B
    Assert.AreEqual < string > ( " a " , b1.Document.Subject);
    Assert.AreEqual < string > ( "" , b1.Document.Body);
    Assert.AreEqual < string > ( "" , b1.Document.Comment);

     //   验证文档并没有流转给C
    Assert.IsNull(c1.Document.Subject);
    Assert.IsNull(c1.Document.Body);
    Assert.IsNull(c1.Document.Comment);

     //   修正错误的内容，重新执行流程
    a1.Write( " a " , " b " , " c " );

     //   验证修订后的内容曾经流转给了B
    Assert.AreEqual < string > ( " a " , b1.Document.Subject);
    Assert.AreEqual < string > ( " b " , b1.Document.Body);
    Assert.AreEqual < string > ( " c " , b1.Document.Comment);

     //   验证修订后的内容也曾经流转给了C
    Assert.AreEqual < string > ( " a " , c1.Document.Subject);
    Assert.AreEqual < string > ( " b " , c1.Document.Body);
    Assert.AreEqual < string > ( " c " , c1.Document.Comment);
}

Output窗口

------ Test started: Assembly: Mediator . Tests . dll ------

A begin write
A write finished

[a]
------------------

()

B received doc from A to review
B begin review
B review failed
A received doc review failed from B
A begin write
A write finished

[a]
------------------
b
( c )

B received doc from A to review
B begin review
B review succeed
C received doc to publish from B
C published
C received doc to archive from B
C archived

1 passed , 0 failed , 0 skipped , took 3.64 seconds ( MSTest 10.0 ).

2、验证“分析第二部” 的设想

定义管理基于事件的中介关系Builder

class EventMediatorBuilder
{
     class ConfigItem
    {
         public Type SourceType { get ; set ; }
         public Type TargetType { get ; set ; }
         public string SourceEventName { get ; set ; }
         public string TargetHandlerMethodName { get ; set ; }

         public override bool Equals( object obj)
        {
             if (obj == null ) throw new ArgumentNullException( " obj " );
            var target = (ConfigItem)obj;
             return
                SourceType == target.SourceType &&
                TargetType == target.TargetType &&
                 string .Equals(SourceEventName, target.SourceEventName) &&
                 string .Equals(TargetHandlerMethodName, target.TargetHandlerMethodName);
        }
    }

    IList < ConfigItem > config = new List < ConfigItem > ();

     public EventMediatorBuilder AddConfig(Type sourceType, Type targetType, string sourceEventName, string targetHandlerMethodName)
    {
         if (sourceType == null ) throw new ArgumentNullException( " sourceType " );
         if (targetType == null ) throw new ArgumentNullException( " targetType " );
         if ( string .IsNullOrEmpty(sourceEventName)) throw new ArgumentNullException( " sourceEventName " );
         if ( string .IsNullOrEmpty(targetHandlerMethodName)) throw new ArgumentNullException( " targetHandlerMethodName " );

         if (sourceType.GetEvent(sourceEventName) == null ) throw new NotSupportedException(sourceEventName);
        var item = new ConfigItem()
        {
            SourceType = sourceType,
            TargetType = targetType,
            SourceEventName = sourceEventName,
            TargetHandlerMethodName = targetHandlerMethodName
        };
         if ( ! config.Contains(item))
            config.Add(item);

         return this ;
    }

     public EventMediatorBuilder BuildAUpColleagues( params object [] colleagues)
    {
         if (colleagues == null ) throw new ArgumentNullException( " colleagues " );
         if (config.Count() == 0 ) return this ;        //   没有通信关系配置项
         if (colleagues.Count() == 1 ) return this ;     //   没有需要配置的关联对象组
        colleagues.ToList().ForEach(x => { if (x == null ) throw new ArgumentNullException(); });

         /// /  限制：不支持一类对象的某个实例同时向另一类对象多个实例的通知
         // if (colleagues.GroupBy(x => x.GetType()).Count() != colleagues.Count())
         //     throw new NotSupportedException();

         foreach (var item in config)
        {
            var sources = colleagues.Where(x => x.GetType() == item.SourceType);
             if ((sources == null ) || (sources.Count() == 0 ))
                 continue ;
            var targets = colleagues.Where(x => x.GetType() == item.TargetType);
             if ((targets == null ) || (targets.Count() == 0 ))
                 continue ;
            var eventInfo = item.SourceType.GetEvent(item.SourceEventName);
             if (eventInfo == null )
                 continue ;
            var methodInfo = item.TargetType.GetMethod(item.TargetHandlerMethodName, BindingFlags.Public | BindingFlags.Instance);
             if (methodInfo == null )
                 continue ;

             //   绑定事件响应关系
             foreach (var source in sources)
                 foreach (var target in targets)
                    eventInfo.AddEventHandler(source, Delegate.CreateDelegate(eventInfo.EventHandlerType, target, methodInfo));
        }

         return this ;
    }
}

实现和单元测试验证

using System;
using System.Diagnostics;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using Microsoft.VisualStudio.TestTools.UnitTesting;
namespace MarvellousWorks.PracticalPattern.Mediator.Tests.Exercise
{
    [TestClass]
     public class DocumentWorkflowMediatorFixture
    {
        Scenario1.A a1;
        Scenario1.B b1;
        Scenario1.C c1;
        Scenario2.A a2;
        Scenario2.B b2;
        Scenario2.C c2;
        Scenario2.D d2;

        EventMediatorBuilder scenario1Builder;
        EventMediatorBuilder scenario2Builder;

         /// <summary>
         /// 配置不同协调关系
         /// 实际项目中可以采用本章介绍的基于配置文件的定义方式
         /// </summary>
        [TestInitialize]
         public void Initialize()
        {
            a1 = new Scenario1.A();
            b1 = new Scenario1.B();
            c1 = new Scenario1.C();
            a2 = new Scenario2.A();
            b2 = new Scenario2.B();
            c2 = new Scenario2.C();
            d2 = new Scenario2.D();

            scenario1Builder = new EventMediatorBuilder()
                 //   1.    A部门拟稿后将文件报B部门审核
                .AddConfig( typeof (Scenario1.A), typeof (Scenario1.B), " WriteDocumentFinishedHandler " , " OnReceiveFileToReview " )
                 //   2.    B部门对于文件审核后，确认文件体例没有缺项后就通知C部门发布
                .AddConfig( typeof (Scenario1.B), typeof (Scenario1.C), " ReviewDocumentSucceedHandler " , " OnReceiveFileToPublish " )
                 //   3.    如果B部门发现文件体例有缺项时，将文件返回给A部门重新修改
                .AddConfig( typeof (Scenario1.B), typeof (Scenario1.A), " ReviewDocumentFailedHandler " , " OnReviewFailed " )
                 //   4.    C部门在接到B部门传来的文件时，先再发布，然后对其归档
                .AddConfig( typeof (Scenario1.C), typeof (Scenario1.C), " DocumentPublishedHandler " , " OnReceiveFileToArchive " );

            scenario2Builder = new EventMediatorBuilder()
                .AddConfig( typeof (Scenario2.A), typeof (Scenario2.B), " WriteDocumentFinishedHandler " , " OnReceiveFileToReview " )
                .AddConfig( typeof (Scenario2.A), typeof (Scenario2.D), " WriteDocumentFinishedHandler " , " OnReceiveFileToArchive " )
                .AddConfig( typeof (Scenario2.B), typeof (Scenario2.A), " ReviewDocumentFailedHandler " , " OnReviewFailed " )
                .AddConfig( typeof (Scenario2.B), typeof (Scenario2.D), " ReviewDocumentFailedHandler " , " OnReceiveFileToArchive " )
                .AddConfig( typeof (Scenario2.B), typeof (Scenario2.C), " ReviewDocumentSucceedHandler " , " OnReceiveFileToPublish " )
                .AddConfig( typeof (Scenario2.C), typeof (Scenario2.D), " DocumentPublishedHandler " , " OnReceiveFileToArchive " );

        }

         /// <summary>
         /// 测试通过Event Mediator Builder构造现有业务流程下的协作关系
         /// </summary>
        [TestMethod]
         public void TestScenario1()
        {
             //   通过Event Mediator以及配置信息建立三个部门Colleague间的协作关系
             //   所有协调关系统一剥离到作为Mediator的.NET事件机制上
            scenario1Builder.BuildAUpColleagues(a1, b1, c1);

             //   成功的路径
            Trace.WriteLine( " Succeed path " );
            a1.Write( " a " , " b " , " c " );

             //   失败的路径
            Trace.WriteLine( " \n\nFailed path " );
            a1.Write( " a " , "" , "" );

             //   修正错误的内容，重新执行流程
            Trace.WriteLine( " Modified after review failed path " );
            a1.Write( " a " , " b " , " c " );
        }

         /// <summary>
         /// 测试通过Event Mediator Builder构造管理层期望的未来业务流程下的协作关系
         /// </summary>
        [TestMethod]
         public void TestScenario2()
        {
             //   通过Event Mediator以及配置信息建立三个部门Colleague间的协作关系
             //   所有协调关系统一剥离到作为Mediator的.NET事件机制上
            scenario2Builder.BuildAUpColleagues(a2, b2, c2, d2);

             //   成功的路径
            Trace.WriteLine( " Succeed path " );
            a2.Write( " a " , " b " , " c " );

             //   失败的路径
            Trace.WriteLine( " \n\nFailed path " );
            a2.Write( " a " , "" , "" );

             //   修正错误的内容，重新执行流程
            Trace.WriteLine( " Modified after review failed path " );
            a2.Write( " a " , " b " , " c " );
        }
    }
}

备注1：现有情景下的A、B、C类型定义

namespace Scenario1
{
     class A : Department
    {
         public event EventHandler < DocumentEventArgs > WriteDocumentFinishedHandler;

         public void Write( string subject, string body, string comment)
        {
             if (Document == null ) throw new NullReferenceException( " Document " );
            Trace.WriteLine( " A begin write " );
            Document.Subject = subject;
            Document.Body = body;
            Document.Comment = comment;
            Trace.WriteLine( " A write finished " );
            Trace.WriteLine(Document);

             if (WriteDocumentFinishedHandler != null )
                WriteDocumentFinishedHandler(

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