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模式設(shè)計(jì)c#－－結(jié)構(gòu)型－－proxy

名稱	Proxy
結(jié)構(gòu)
意圖	為其他對(duì)象提供一種代理以控制對(duì)這個(gè)對(duì)象的訪問。
適用性	在需要用比較通用和復(fù)雜的對(duì)象指針代替簡單的指針的時(shí)候，使用P r o x y 模式。下面是一些可以使用P r o x y 模式常見情況： 1) 遠(yuǎn)程代理（Remote Proxy ）為一個(gè)對(duì)象在不同的地址空間提供局部代表。 NEXTSTEP[Add94] 使用N X P r o x y 類實(shí)現(xiàn)了這一目的。Coplien[Cop92] 稱這種代理為“大使” （A m b a s s a d o r ）。 2 )虛代理（Virtual Proxy ）根據(jù)需要?jiǎng)?chuàng)建開銷很大的對(duì)象。在動(dòng)機(jī)一節(jié)描述的I m a g e P r o x y 就是這樣一種代理的例子。 3) 保護(hù)代理（Protection Proxy ）控制對(duì)原始對(duì)象的訪問。保護(hù)代理用于對(duì)象應(yīng)該有不同的訪問權(quán)限的時(shí)候。例如，在C h o i c e s 操作系統(tǒng)[ C I R M 9 3 ]中K e m e l P r o x i e s 為操作系統(tǒng)對(duì)象提供了訪問保護(hù)。 4 )智能指引（Smart Reference ）取代了簡單的指針，它在訪問對(duì)象時(shí)執(zhí)行一些附加操作。它的典型用途包括：對(duì)指向?qū)嶋H對(duì)象的引用計(jì)數(shù)，這樣當(dāng)該對(duì)象沒有引用時(shí)，可以自動(dòng)釋放它(也稱為S m a r tP o i n t e r s[ E d e 9 2 ] )。當(dāng)?shù)谝淮我靡粋€(gè)持久對(duì)象時(shí)，將它裝入內(nèi)存。在訪問一個(gè)實(shí)際對(duì)象前，檢查是否已經(jīng)鎖定了它，以確保其他對(duì)象不能改變它。

Code Example

namespace?Proxy_DesignPattern

{

????using?System;

????using?System.Threading;

????///?<summary>

????///????Summary?description?for?Client.

????///?</summary>

????abstract?class?CommonSubject?

????{

????????abstract?public?void?Request();????????

????}

????class?ActualSubject?:?CommonSubject

????{

????????public?ActualSubject()

????????{

????????????//?Assume?constructor?here?does?some?operation?that?takes?quite?a

????????????//?while?-?hence?the?need?for?a?proxy?-?to?delay?incurring?this?

????????????//?delay?until?(and?if)?the?actual?subject?is?needed

????????????Console.WriteLine("Starting?to?construct?ActualSubject");????????

????????????Thread.Sleep(1000);?//?represents?lots?of?processing!?

????????????Console.WriteLine("Finished?constructing?ActualSubject");

????????}

????????????

????????????override?public?void?Request()

????????{

????????????Console.WriteLine("Executing?request?in?ActualSubject");

????????}

????}

????class?Proxy?:?CommonSubject

????{

????????ActualSubject?actualSubject;

????????override?public?void?Request()

????????{

????????????if?(actualSubject?==?null)

????????????????actualSubject?=?new?ActualSubject();

????????????actualSubject.Request();

????????}????

????????

????}

????

????public?class?Client

????{

????????public?static?int?Main(string[]?args)

????????{

????????????Proxy?p?=?new?Proxy();

????????????//?Perform?actions?here

????????????//?.?.?.?

????????????if?(1==1)????????//?at?some?later?point,?based?on?a?condition,?

????????????????p.Request();//?we?determine?if?we?need?to?use?subject

????????????????????????????????

????????????return?0;

????????}

????}

}

//?Proxy?pattern?--?Real?World?example??

using?System;

namespace?DoFactory.GangOfFour.Proxy.RealWorld

{

??//?Mainapp?test?application?

??class?MainApp

??{

????static?void?Main()

????{

??????//?Create?math?proxy?

??????MathProxy?p?=?new?MathProxy();

??????//?Do?the?math?

??????Console.WriteLine("4?+?2?=?"?+?p.Add(4,?2));

??????Console.WriteLine("4?-?2?=?"?+?p.Sub(4,?2));

??????Console.WriteLine("4?*?2?=?"?+?p.Mul(4,?2));

??????Console.WriteLine("4?/?2?=?"?+?p.Div(4,?2));

??????//?Wait?for?user?

??????Console.Read();

????}

??}

??//?"Subject"?

??public?interface?IMath

??{

????double?Add(double?x,?double?y);

????double?Sub(double?x,?double?y);

????double?Mul(double?x,?double?y);

????double?Div(double?x,?double?y);

??}

??//?"RealSubject"?

??class?Math?:?IMath

??{

????public?double?Add(double?x,?double?y){return?x?+?y;}

????public?double?Sub(double?x,?double?y){return?x?-?y;}

????public?double?Mul(double?x,?double?y){return?x?*?y;}

????public?double?Div(double?x,?double?y){return?x?/?y;}

??}

??//?"Proxy?Object"?

??class?MathProxy?:?IMath

??{

????Math?math;

????public?MathProxy()

????{

??????math?=?new?Math();

????}

????public?double?Add(double?x,?double?y)

????{?

??????return?math.Add(x,y);?

????}

????public?double?Sub(double?x,?double?y)

????{?

??????return?math.Sub(x,y);?

????}

????public?double?Mul(double?x,?double?y)

????{?

??????return?math.Mul(x,y);?

????}

????public?double?Div(double?x,?double?y)

????{?

??????return?math.Div(x,y);?

????}

??}

}

posted on 2006-01-03 15:51 夢(mèng)在天涯閱讀(935) 評(píng)論(2) 編輯收藏引用所屬分類: Design pattern

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# re: 模式設(shè)計(jì)c#－－結(jié)構(gòu)型－－proxy 2006-04-24 16:05 夢(mèng)在天涯

好像和裝飾（Decorator）模式差不多啊?

到底有什么不同啊? 回復(fù) 更多評(píng)論

# re: 模式設(shè)計(jì)c#－－結(jié)構(gòu)型－－proxy 2006-04-24 16:05 夢(mèng)在天涯

我想Proxy與Adapter還是有區(qū)別的。因?yàn)镻roxy中的代理和被代理對(duì)象是“同根生”，這樣才可以代理。Adapter中的Adapter與Adaptee不用“同根生”。我把Proxy稱作“票販子的模式”，而Adapter是“倒賣外匯的模式”。票販子販的是票，在販賣的過程中，票沒有變化，只是被代理了。而Adapter模式中，外匯可能由人民幣變做了美元，東西變了（呵呵，換湯不換藥，都是鈔票）。回復(fù) 更多評(píng)論

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# re: 模式設(shè)計(jì)c#－－結(jié)構(gòu)型－－proxy 2006-04-24 16:05 夢(mèng)在天涯

# re: 模式設(shè)計(jì)c#－－結(jié)構(gòu)型－－proxy 2006-04-24 16:05 夢(mèng)在天涯

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