代理設計模式中主類的代碼是什麼？

Question

請幫我創建此代理設計模式的主類？

//Filename:Payment.java

import java.math.*; import java.rmi.*; 
    public interface Payment extends Remote{ 
    public void purchase(PaymentVO payInfo, BigDecimal price) 
     throws PaymentException, RemoteException; } 

//文件名：PaymentException.java

`public class PaymentException extends Exception{ 
    public PaymentException(String m){ 
     super(m); 
    } 
    public PaymentException(String m, Throwable c){ 
     super(m, c); 
    } 
}` 

//Filename:PaymentImpl.java

`import java.math.*; 
    import java.net.*; 
    import java.rmi.*; 
    import java.rmi.server.*; 
      public class PaymentImpl implements Payment{ 
      private static final String PAYMENT_SERVICE_NAME = "paymentService"; 

     public PaymentImpl() throws RemoteException, MalformedURLException{ 
    UnicastRemoteObject.exportObject(this); 
    Naming.rebind(PAYMENT_SERVICE_NAME, this); 
} 
public void purchase(PaymentVO payInfo, BigDecimal price) 
    throws PaymentException{ 
} 

}`

//文件名：Paym entService.java

import java.math.*; 
public interface PaymentService{ 
    public void purchase(PaymentVO payInfo, BigDecimal price) 
     throws PaymentException, ServiceUnavailableException; 
} 

//文件名：PaymentVO.java

public class PaymentVO{ 
} 

//文件名：ServiceUnavailableException.java

public class ServiceUnavailableException extends Exception{ 
public ServiceUnavailableException(String m){ 
    super(m); 
} 
public ServiceUnavailableException(String m, Throwable c){ 
    super(m, c); 
} 

}

Answer 1

，給予代理的類圖下面設計模式來自：http://www.codeproject.com/Articles/186001/Proxy-Design-Pattern

在你的問題中，你有一個支付界面，這是「主題」。然後你有PaymentImpl實現支付接口，這是「真正的主題」。但是，您在這裏錯過了「代理」。

您需要編寫一個PaymentProxy類，該類還將實現支付接口。這個類將引用「Real Subject」（PaymentImpl）類型的對象作爲私有字段，並將通過此「Real Subject」對象調用從「Subject」繼承的方法。

例子：

public class PaymentProxy implements Payment{ 

    private PaymentImpl realPayment; 

    public PaymentProxy(){ 

    } 

    public void purchase(PaymentVO payInfo, BigDecimal price) throws PaymentException{ 
     if(realPayment==null){ 
      realPayment = new PaymentImpl(); 
     } 
     realPayment.purchase(payInfo, price); 
    } 
} 

您可能會注意到realPayment是按需使用代理設計模式時創建的。當對象創建昂貴時，這非常有用。

以下是主類代碼：

public class Client{ 
    public static void main(String[] args){ 

     PaymentProxy paymentProxy = new PaymentProxy(); //note that the real proxy object is not yet created 
     //... code for resolving payInfo and price as per the requirement 
     paymentProxy.purchase(payInfo, price); //this is where the real payment object of type PaymentImpl is created and invoked 


    } 

}