Re: [aspectj-users] Mixins with @DeclareParents (M5)

[Brian Ericson <bme@xxxxxxxx>]

Some progress...  Moving everything to a "test" package and changing the 
declaration to:
@DeclareParents("@test.PersistentEntity test.*")
is enough to get AspectJ markers in Eclipse.  However, an attempt to 
construct an instance of Test fails with the following exception:
java.lang.VerifyError: (class: test/Test, method: setId signature: (J)V) 
Register pair 0/1 contains wrong type

I also reworked the "moody" example (in the documentation and sited in a 
thread below) using a Persistent interface and PersistentImpl 
implementation outside of the aspect, allowing me to do the following:
package test;

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.DeclareParents;

@Aspect
public class PersistentEntityAspect {
  @DeclareParents("@test.PersistentEntity test.*")
  public static Persistent introduced = new PersistentImpl();
}

This fails with the same exception above.  What am I doing wrong?  This 
works for Adrian... (see 
http://www-128.ibm.com/developerworks/java/library/j-aopwork8/ ).

Brian Ericson wrote:

> I'm trying to implement mixins using the @Aspect/@DeclareParents 
> annotations.  To begin with, the following works:
> PersistentEntity.java:
> public @interface PersistentEntity { }
>
> PersistentEntityAspect.aj:
> public aspect PersistentEntityAspect {
>   public interface Persistent {
>      long getId();
>      void setId(long id);
>   }
>  
>   declare parents : @PersistentEntity * implements Persistent;
>  
>   long Persistent.id = 0;
>  
>   public long Persistent.getId() { return id; }
>   public void Persistent.setId(long id) { this.id = id; }
> }
>
> Test.java:
> @PersistentEntity
> public class Test { }
>
> Using Jython, I can see that Test implements 
> PersistentEntityAspect.Persistent and can call both getId() and setId().
>
> The following does not work (replacing PersistentEntityAspect.aj with 
> PersistentEntityAspect.java):
> import org.aspectj.lang.annotation.Aspect;
> import org.aspectj.lang.annotation.DeclareParents;
>
> @Aspect
> public class PersistentEntityAspect {
>   public interface Persistent {
>      long getId();
>      void setId(long id);
>   }
>  
>   public class PersistentImpl implements Persistent {
>      long id;
>          public long getId() { return id; }
>      public void setId(long id) { this.id = id; }
>   }
>  
>   @DeclareParents("@PersistentEntity *")
>   public static Persistent introduced = new 
> PersistentEntityAspect().new PersistentImpl();
> }
>
> Test is not advised and does not implement any interface.  (I did use 
> the recent thread 
> http://dev.eclipse.org/mhonarc/lists/aspectj-users/msg05032.html as 
> reference, but this neither compiled (... introduced = new 
> MoodyImpl();) nor did I get the advice bit working out.  I must be 
> doing something simple wrong (maybe I need to post-compile the result 
> to weave it or use load-time weaving?  I'm not sure how to do either 
> (more research!))...
>
> Other questions...  Eclipse/AJDT does not allow me to use methods 
> introduced by advice.  For example, Test.java could not look as follows:
> public Test {
>   long test { return getId(); }
> }
>
> This actually compiles and runs correctly using ajc, but won't get 
> compile in the IDE (The method getId() is undefined...).
>
> Also, how're people using AspectJ with Maven 2?  Confessing to be a 
> newbie to both AspectJ and Maven, I'm currently "tricking" it by using 
> ajc as my java compiler.
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