iPOJO and abstract component classes

[Trejkaz <tr...@trypticon.org>]

Hi all.

I have a setup where a lot of concrete service classes happened to
have identical logic, so I wanted to abstract that logic to an
abstract class.  But it looks like what happens is that iPOJO won't
inject parameters unless they are on the bottom-level concrete class.

In other words, I'm trying to do this:

  public interface Service {
    void doComplicatedStuff();
  }

  @Component
  public class AbstractService implements Service {
    @Requires
    private OtherService otherService;

    @Override
    public void doComplicatedStuff() {
      // ... complicated logic using otherService ...
    }
  }

  @Component
  @Provides
  public class ConcreteService extends AbstractService {
  }

And when I get to doComplicatedStuff(), otherService is always null.

Does the iPOJO voodoo just not support this situation?  The same logic
with the same service on the concrete class works fine so I expected
it to work here too, and I didn't see any warnings at the time it
mangled the classes or at runtime, indicating any problem...

TX

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Re: iPOJO and abstract component classes

[Clement Escoffier <cl...@gmail.com>]

Hi,

On 10.01.2009, at 08:08, Trejkaz wrote:

> Hi all.
>
> I have a setup where a lot of concrete service classes happened to
> have identical logic, so I wanted to abstract that logic to an
> abstract class.  But it looks like what happens is that iPOJO won't
> inject parameters unless they are on the bottom-level concrete class.

That's true

>
>
> In other words, I'm trying to do this:
>
>  public interface Service {
>    void doComplicatedStuff();
>  }
>
>  @Component
>  public class AbstractService implements Service {
>    @Requires
>    private OtherService otherService;
>
>    @Override
>    public void doComplicatedStuff() {
>      // ... complicated logic using otherService ...
>    }
>  }
>
>  @Component
>  @Provides
>  public class ConcreteService extends AbstractService {
>  }
>
> And when I get to doComplicatedStuff(), otherService is always null.

iPOJO manipulates the implementation class to support field injection.  
So, parent class fields are not injected. However, bind and unbind  
methods are supported . So, you can change your class as follow :


>  @Component
>  public class AbstractService implements Service {
>    private OtherService otherService;

       public synchronized void bindOtherService(OtherService svc) {
		otherService = svc;
        }


       public synchronized void unbindOtherService(OtherService svc) {
		otherService = null;
        }
>
>    @Override
>    public synchronized void doComplicatedStuff() {
>      // ... complicated logic using otherService ...
>    }
>  }


With the following metadata:
<ipojo>
     <component classname="...ConcreteService">
	<requires interfqce="...OtherService">
		<callback type="bind" method="bindOtherService"/>
                 <callback type="unbind" method="unbindOtherService"/>
        </requires>
    </component>
</ipojo>

>
>
> Does the iPOJO voodoo just not support this situation?  The same logic
> with the same service on the concrete class works fine so I expected
> it to work here too, and I didn't see any warnings at the time it
> mangled the classes or at runtime, indicating any problem...

  iPOJO should warn you that a field does not exist in the class, and  
the component type cannot be started correctly. I will check it...


Regards,


Clement





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