软件工程 设计模式学习之代理模式Proxy

今天说一下代理模式.
从名字看大家都知道了代理模式,就是一个让一个类来帮你干某些事.是吧?嘿嘿.当然开始之前我们还是惯例来看看这个设计模式的UML:

我看到了代理类请求其实调用的还是RealRequest类的请求,只是Proxy去调用

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我们现在来用代码说话了:
第一个还是PHP

 1 abstract class CommRequest{   
 2     abstract public function Request();   
 3 }  
 4 
 5 abstract class CommRequest{
 6     abstract public function Request();
 7 }
 8 class ActualRequest extends CommRequest{   
 9     public function Request() {   
10     echo("Actual Request !\n");   
11     }  
12 
13 class ActualRequest extends CommRequest{
14     public function Request() {
15  echo("Actual Request !\n");
16     }
17 class PHPProxy extends CommRequest {   
18     private $realRequest;   
19     public function Request() {   
20         if(isset($this->realRequest)){   
21             echo("Proxy Here!\n");   
22             $this->realRequest->Request();   
23         }   
24     }   
25 }  
26 
27 class PHPProxy extends CommRequest {
28  private $realRequest;
29  public function Request() {
30   if(isset($this->realRequest)){
31    echo("Proxy Here!\n");
32    $this->realRequest->Request();
33   }
34  }
35 } 
36 
37 $p = new PHPProxy();
38 $p->Request();
39 

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接下来来看看C#的代码.

  1 namespace Proxy_DesignPattern   
  2 {   
  3     using System;   
  4     using System.Threading;   
  5   
  6     /// <SUMMARY></SUMMARY>   
  7     ///    Summary description for Client.   
  8     ///    
  9     abstract class CommonSubject   
 10     {   
 11         abstract public void Request();   
 12     }   
 13   
 14     class ActualSubject : CommonSubject   
 15     {   
 16         public ActualSubject()   
 17         {   
 18             // Assume constructor here does some operation that takes quite a   
 19             // while - hence the need for a proxy - to delay incurring this    
 20             // delay until (and if) the actual subject is needed   
 21             Console.WriteLine("Starting to construct ActualSubject");   
 22             Thread.Sleep(1000); // represents lots of processing!    
 23             Console.WriteLine("Finished constructing ActualSubject");   
 24         }   
 25   
 26         override public void Request()   
 27         {   
 28             Console.WriteLine("Executing request in ActualSubject");   
 29         }   
 30     }   
 31   
 32     class Proxy : CommonSubject   
 33     {   
 34         ActualSubject actualSubject;   
 35   
 36         override public void Request()   
 37         {   
 38             if (actualSubject == null)   
 39                 actualSubject = new ActualSubject();   
 40             actualSubject.Request();   
 41         }   
 42   
 43     }   
 44   
 45     public class Client   
 46     {   
 47         public static int Main(string[] args)   
 48         {   
 49             Proxy p = new Proxy();   
 50   
 51             // Perform actions here   
 52             // . . .    
 53   
 54             if (1 == 1)     // at some later point, based on a condition,    
 55                 p.Request();// we determine if we need to use subject   
 56   
 57             return 0;   
 58         }   
 59     }   
 60 }  
 61 
 62 namespace Proxy_DesignPattern
 63 {
 64     using System;
 65     using System.Threading;
 66 
 67     /// 
 68     ///    Summary description for Client.
 69     /// 
 70     abstract class CommonSubject
 71     {
 72         abstract public void Request();
 73     }
 74 
 75     class ActualSubject : CommonSubject
 76     {
 77         public ActualSubject()
 78         {
 79             // Assume constructor here does some operation that takes quite a
 80             // while - hence the need for a proxy - to delay incurring this 
 81             // delay until (and if) the actual subject is needed
 82             Console.WriteLine("Starting to construct ActualSubject");
 83             Thread.Sleep(1000); // represents lots of processing! 
 84             Console.WriteLine("Finished constructing ActualSubject");
 85         }
 86 
 87         override public void Request()
 88         {
 89             Console.WriteLine("Executing request in ActualSubject");
 90         }
 91     }
 92 
 93     class Proxy : CommonSubject
 94     {
 95         ActualSubject actualSubject;
 96 
 97         override public void Request()
 98         {
 99             if (actualSubject == null)
100                 actualSubject = new ActualSubject();
101             actualSubject.Request();
102         }
103 
104     }
105 
106     public class Client
107     {
108         public static int Main(string[] args)
109         {
110             Proxy p = new Proxy();
111 
112             // Perform actions here
113             // . . . 
114 
115             if (1 == 1)  // at some later point, based on a condition, 
116                 p.Request();// we determine if we need to use subject
117 
118             return 0;
119         }
120     }
121 }
122 
123 

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最后的舞台还是留给Delphi了.

 1 type 
 2   ICommRequest = interface 
 3     procedure Request; 
 4   end; 
 5 
 6   TActualRequest = class(TInterfacedObject,ICommRequest) 
 7   public 
 8     procedure Request; 
 9   end; 
10 
11   TProxy = class(TInterfacedObject,ICommRequest) 
12   private 
13     FRealRequest:TActualRequest; 
14   public 
15     procedure Request; 
16     property RealRequest:TActualRequest  read FRealRequest write FRealRequest; 
17   end; 
18 
19 { TProxy } 
20 
21 procedure TProxy.Request; 
22 begin 
23   if Assigned(RealRequest) then 
24   begin 
25     Writeln('Proxy!'); 
26     RealRequest.Request; 
27   end; 
28 end; 
29 
30 { TActualRequest } 
31 
32 procedure TActualRequest.Request; 
33 begin 
34   Writeln('Actual Request'); 
35 end; 
36 
37 var 
38   tmp:string; 
39   P:TProxy; 
40   A:TActualRequest; 
41 begin 
42   P:=TProxy.Create; 
43   A:=TActualRequest.Create; 
44   try 
45     P.RealRequest:=A; 
46     P.Request; 
47     Readln(tmp); 
48   finally 
49     A.Free; 
50     P.Free; 
51   end; 
52 end. 
53 

好的.其实这个模式很简单,希望对大家有帮助.