Re: [Springframework-developer] CGLIB question

[Rod J. <rod...@in...>]

Chris,

Actually I guess what I'm trying to do here doesn't make sense, and that
CGLIB's behavior is correct.

I need to override the method to invoke the original target via reflection.
Otherwise I guess CGLIB creates a new subclass that won't invoke my
instance, which is in the state I want after its properties have been set.

Does CGLIB provide any way of copying the state from my original instance of
the class into the new subclass? Or would I need to write code to do that
manually, assuming I could rely on the no-arg constructor and copy JavaBean
properties?

Regards,
Rod

----- Original Message ----- 
From: "Rod Johnson" <rod...@in...>
To: <spr...@li...>
Sent: Friday, November 28, 2003 2:47 PM
Subject: [Springframework-developer] CGLIB question


> Chris,
>
> I'm sure you can help with this one.
>
> I guessed that the CGLIB MethodFilter interface was what I needed to get
> CGLIB override to get only those methods with advice overloaded. However,
> when I do that I find that behavior changes.
>
> Here's how I've changed the inner classes in
> org.springframework.aop.framework.AopProxy. I want only methods that have
an
> advice chain to be proxied.
>
>
>  private class CglibProxyFactory {
>
>   private Object createProxy() {
>    try {
>     return Enhancer.enhance(advised.getTarget().getClass(),
>      completeProxiedInterfaces(),
>      new MethodInterceptor() {
>       public Object intercept(Object handler, Method method, Object[]
> objects, MethodProxy methodProxy) throws Throwable {
>        return invoke(handler, method, objects);
>       }
>      },
> // I've added the three following arguments
>      null,  // ClassLoader: use default
>      null, // Method replace: what does this mean? I couldn't work out
from
> CGLIB Javadoc
>      new SelectiveOverrideMethodFilter()
>     );
>    }
>    catch (CodeGenerationException ex) {
>     throw new AspectException("Couldn't generate CGLIB subclass of class
'"
> + advised.getTarget().getClass() + "': " +
>       "Common causes of this problem include using a final class, or a
> non-visible class", ex);
>    }
>   }
>  }
>
>
>  private class SelectiveOverrideMethodFilter implements MethodFilter {
>
>   public boolean accept(Member member) {
>    // Proxy is not yet available, but that shouldn't matter
>    //List chain =
>
advised.getAdvisorChainFactory().getInterceptorsAndDynamicInterceptionAdvice
> (advised, null, (Method) member, advised.getTarget().getClass());
>    //return !chainIsOptimizableToDirectTargetInvocation(chain);
>    return true;
>   }
>
>  }
>
> The two lines I've commented out in the accept() method produce a 2.5x
> performance improvement in non-advised methods (as you'd expect) but they
> also produce different behavior, compared to returning true.
>
> It appears that now CGLIB is creating a new instance of the target and
> somehow now copying its state. Previously a property I'd set on the target
> was visible through the proxy; now it isn't.
>
> Overall I really like CGLIB: it does what I expect of it with no fuss, and
> it's a cool concept. But the Javadoc really is inadequate.
>
> Regards,
> Rod
>
>
>
>
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