Re: accessing subclasse methods and fields with introspection / reflection

From:
"Samy" <samy@samy.com>
Newsgroups:
comp.lang.java.help
Date:
Thu, 3 Aug 2006 11:40:17 +0200
Message-ID:
<easemo$s9p$1@reader1.imaginet.fr>
hmm, it happens that I can't use it that straight forward. The way you call
it you make a reference to class D. which I can't do when i am in class A.

The main problem is : 'Can an object know it's instanciation type?'.
From a purely object point of view it is impossible. An object doesn't have
to know anything from it's derived objects. This is just impossible.
But if it can't be done by the object by it's own resources, maybe it can be
achieved from the external. If the JVM could be asked by an object what it's
instanciation class is, it would solve my problem. But I have no idea of how
to do it ;-(

Does anyone have a clue ?

"Samy" <samy@samy.com> wrote in message
news:easa53$rdm$1@reader1.imaginet.fr...

I didn't know of that proxy class. I will check in that area. Thank you

"Remi Arntzen" <Remi.Arntzen@gmail.com> wrote in message
news:1154543577.335649.21480@i42g2000cwa.googlegroups.com...

Samy wrote:

Hi everyone,

Now I would like to have a A.listMyMethods() which would return all the
processA, processB, processC and processD (since they are all abstract
except D meaning that an instance of my classes would could not be
something
else than D)


I took a quick look at the java.lang.Class documentation and couldn't
find a way to find a way to determin it's subclasses.

From my tests, when I instanciate a D object and invoke a
myDObject.getClass().getMethods() I have what I want. But what I really
would want is to call myDObject.listMyMethods(). So that the object
itself
would tell me it's methods.


java.lang.reflect.Proxy.newProxyInstance(D.getClass().getClassLoader(),
blah, k);

where k = new InvocationHandler() {
       Object invoke(Object proxy, Method method, Object[] args)
throws Throwable {
           if (method.getName() == "listMyMethods") {
               return proxy.getClass().getMethods();
           } else {
               return method.invoke(proxy, args);
           }
       }
}

pragmatically override any method. muhahahaaaa!
also note that I haven't actually used this method in a while, so my
understanding of it might not be completely accurate/(work at all).

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