黄江镇长龙小学:设计模式22：Mediator Pattern (调解者模式)

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设计模式22：Mediator Pattern (调解者模式)

分类：设计模式 2009-07-09 13:42 131人阅读评论(0) 收藏举报

英文原文：http://www.dofactory.com/Patterns/PatternMediator.aspx

一、Mediator Pattern (调解者模式)的定义

Define an object that encapsulates how a set of objects interact. Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it lets you vary their interaction independently.

定义一个对象将一系列对象如何相互作用的操作进行封装。调解者通过避免一个对象明确指向其余的对象来促使自由耦合，同时能够让你单独的改变他们之间的相互作用。

二、UML类图

Mediator (IChatroom)

定义一个接口用于与同事级对象进行通信

ConcreteMediator (Chatroom)

通过与同事级对象进行对等来实现相互协作行为
知道并且维持本身的同事级对象

Colleague classes (Participant)

每个同事级对象都知道自己的调节者对象
每个同事级对象在与另外的同事级对象进行通信时必须要与调节者进行通信。

三、调解者模式实例代码

view plain

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Mediator_Pattern
{
///
/// MainApp startup class for Structural
/// Mediator Design Pattern.
///
class MainApp
{
///
/// Entry point into console application.
///
static void Main()
{
ConcreteMediator m = new ConcreteMediator();
ConcreteColleague1 c1 = new ConcreteColleague1(m);
ConcreteColleague2 c2 = new ConcreteColleague2(m);
m.Colleague1 = c1;
m.Colleague2 = c2;
c1.Send("How are you?");
c2.Send("Fine, thanks");
// Wait for user
Console.ReadKey();
}
}
///
/// The 'Mediator' abstract class
///
abstract class Mediator
{
public abstract void Send(string message,
Colleague colleague);
}
///
/// The 'ConcreteMediator' class
///
class ConcreteMediator : Mediator
{
private ConcreteColleague1 _colleague1;
private ConcreteColleague2 _colleague2;
public ConcreteColleague1 Colleague1
{
set { _colleague1 = value; }
}
public ConcreteColleague2 Colleague2
{
set { _colleague2 = value; }
}
public override void Send(string message,
Colleague colleague)
{
if (colleague == _colleague1)
{
_colleague2.Notify(message);
}
else
{
_colleague1.Notify(message);
}
}
}
///
/// The 'Colleague' abstract class
///
abstract class Colleague
{
protected Mediator mediator;
// Constructor
public Colleague(Mediator mediator)
{
this.mediator = mediator;
}
}
///
/// A 'ConcreteColleague' class
///
class ConcreteColleague1 : Colleague
{
// Constructor
public ConcreteColleague1(Mediator mediator)
: base(mediator)
{
}
public void Send(string message)
{
mediator.Send(message, this);
}
public void Notify(string message)
{
Console.WriteLine("Colleague1 gets message: "
+ message);
}
}
///
/// A 'ConcreteColleague' class
///
class ConcreteColleague2 : Colleague
{
// Constructor
public ConcreteColleague2(Mediator mediator)
: base(mediator)
{
}
public void Send(string message)
{
mediator.Send(message, this);
}
public void Notify(string message)
{
Console.WriteLine("Colleague2 gets message: "
+ message);
}
}
}

四、另外一个使用调解者模式的实例代码

这个现实世界中的代码演示了Mediator模式，促进注册调停者的不同参与者之间的松耦合通信。调停者是中央枢纽，所有通信通过它发生。在这一点上，只有一到一个通讯在调停者中实施，但会是情谊的改变到一到多。

view plain

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Mediator_Pattern
{
///
/// MainApp startup class for Real-World
/// Mediator Design Pattern.
///
class MainApp
{
///
/// Entry point into console application.
///
static void Main()
{
// Create chatroom
Chatroom chatroom = new Chatroom();
// Create participants and register them
Participant George = new Beatle("George");
Participant Paul = new Beatle("Paul");
Participant Ringo = new Beatle("Ringo");
Participant John = new Beatle("John");
Participant Yoko = new NonBeatle("Yoko");
chatroom.Register(George);
chatroom.Register(Paul);
chatroom.Register(Ringo);
chatroom.Register(John);
chatroom.Register(Yoko);
// Chatting participants
Yoko.Send("John", "Hi John!");
Paul.Send("Ringo", "All you need is love");
Ringo.Send("George", "My sweet Lord");
Paul.Send("John", "Can't buy me love");
John.Send("Yoko", "My sweet love");
// Wait for user
Console.ReadKey();
}
}
///
/// The 'Mediator' abstract class
///
abstract class AbstractChatroom
{
public abstract void Register(Participant participant);
public abstract void Send(
string from, string to, string message);
}
///
/// The 'ConcreteMediator' class
///
class Chatroom : AbstractChatroom
{
private Dictionary _participants =
new Dictionary();
public override void Register(Participant participant)
{
if (!_participants.ContainsValue(participant))
{
_participants[participant.Name] = participant;
}
participant.Chatroom = this;
}
public override void Send(
string from, string to, string message)
{
Participant participant = _participants[to];
if (participant != null)
{
participant.Receive(from, message);
}
}
}
///
/// The 'AbstractColleague' class
///
class Participant
{
private Chatroom _chatroom;
private string _name;
// Constructor
public Participant(string name)
{
this._name = name;
}
// Gets participant name
public string Name
{
get { return _name; }
}
// Gets chatroom
public Chatroom Chatroom
{
set { _chatroom = value; }
get { return _chatroom; }
}
// Sends message to given participant
public void Send(string to, string message)
{
_chatroom.Send(_name, to, message);
}
// Receives message from given participant
public virtual void Receive(
string from, string message)
{
Console.WriteLine("{0} to {1}: '{2}'",
from, Name, message);
}
}
///
/// A 'ConcreteColleague' class
///
class Beatle : Participant
{
// Constructor
public Beatle(string name)
: base(name)
{
}
public override void Receive(string from, string message)
{
Console.Write("To a Beatle: ");
base.Receive(from, message);
}
}
///
/// A 'ConcreteColleague' class
///
class NonBeatle : Participant
{
// Constructor
public NonBeatle(string name)
: base(name)
{
}
public override void Receive(string from, string message)
{
Console.Write("To a non-Beatle: ");
base.Receive(from, message);
}
}
}

五、中介者模式的优点

1. 将系统按功能分割成更小的对象，符合类的最小设计原则

2. 对关联对象的集中控制

3. 减小类的耦合程度，明确类之间的相互关系：当类之间的关系过于复杂时，其中任何一个类的修改都会影响到其他类，不符合类的设计的开闭原则，而Mediator模式将原来相互依存的多对多的类之间的关系简化为Mediator控制类与其他关联类的一对多的关系，当其中一个类修改时，可以对其他关联类不产生影响（即使有修改，也集中在Mediator控制类）。

4. 有利于提高类的重用性

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