Sunday, April 01, 2007

 

Default Interface Implementation

這是AspectJ in Action8.5.4 Providing a default interface implementation中的程式碼

With OOP


public interface Nameable {
   public void setName(String name);

   public String getName();
}
===============================================================================
public interface Identifiable {
   public void setId(String id);

   public String getId();
}
===============================================================================
public class Entity implements Nameable, Identifiable {
   private String _name;
   
   private String _id;
   
   public void setName(String name) {
      _name = name;
   }

   public String getName() {
      return _name;
   }

   public void setId(String id) {
      _id = id;
   }

   public String getId() {
      return _id;
   }
}

With AOP


public interface Nameable {
   public void setName(String name);

   public String getName();

   static aspect Impl {
      private String Nameable._name;

      public void Nameable.setName(String name) {
         _name = name;
      }

      public String Nameable.getName() {
         return _name;
      }
   }
}
===============================================================================
public interface Identifiable {
   public void setId(String id);

   public String getId();

   static aspect Impl {
      private String Identifiable._id;

      public void Identifiable.setId(String id) {
         _id = id;
      }

      public String Identifiable.getId() {
         return _id;
      }
   }
}
===============================================================================
public class Entity implements Nameable, Identifiable {
}

有了AOP後
Default Implementation不再是class與abstract class的專利
看看上面的程式碼
想想自己系統中多少domain object有name與id這兩個property
就會知道這個AOP Idiom可以省下多少行程式
不過設計上要更小心是一定的
另外AJDT對於這些introduction進來的field與method
似乎還沒有辦法用快捷鍵則是比較麻煩的地方

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