Proxying with Generics

Question

I use java.lang.reflect.Proxy to proxy objects.

I have this class:

public class TransportableImpl extends Transportable{
  public class OrderInvoker extends InvocationHandler{
           ...
  }
}

Here i build the Proxy:

Transportable t = new TransportableImpl();
Order myOrder = new OrderImpl();
Class proxyClass = Proxy.getProxyClass(getClass().getClassLoader(), Transportable.class, Order.class);
Object serializable = proxyClass.getConstructor(new Class[]{InvocationHandler.class}).newInstance(t.new OrderInvoker(myOrder));

Problem is: Class is raw type and

Class<? extends Order & Transportable> proxyClass =
     (Class<? extends Order & Transportable>) 
     Proxy.getProxyClass(getClass().getClassLoader(), 
     Transportable.class, Order.class);

is hard to read.

Any ideas?

Counter question: what would you like to write, i.e. what would you consider precise enough and yet easy to read? Can you provide some pseudo code which would help us understand what you're aiming at? — Thomas, Jan 09 '14 at 13:39
If it's about readability, I would suggest to move this question to CodeReview http://codereview.stackexchange.com/ — Raffaele Rossi, Jan 09 '14 at 13:41
The fact that you are using a raw class is only a problem if you were planning on using the generic type arguments, but I don't see how. — Sotirios Delimanolis, Jan 09 '14 at 14:31
`Class extends Order & Transportable>` is invalid syntax anyway. — Paul Bellora, Jan 09 '14 at 17:09

score 2 · Accepted Answer · answered Jan 09 '14 at 18:49

The Proxy#getProxyClass(ClassLoader, Class) method is declared as

public static Class<?> getProxyClass(ClassLoader loader,
                                     Class<?>... interfaces)

Its return type is therefore Class<?>. The normal syntax would be

Class proxyClass<?> = Proxy.getProxyClass(getClass().getClassLoader(), Transportable.class, Order.class);

Technically you could do (with a warning)

public <T extends Order & Transportable> void doSomething() {
    Class<T> proxyClass = (Class<T>) Proxy.getProxyClass(Driver.class.getClassLoader(),
            Transportable.class, Order.class);
}

but that gains you nothing as you will pretty much never need to use that T variable. The Class class provides very little methods that makes use of it, namely getConstructor(Class...) and newInstance(). But again, the whole point of reflection is that you only know the class types at run time, not at compile time where generics are useful.

Yes, thats it. I named it PROXY instead of T. – Grim Jan 10 '14 at 10:25 — Grim, Jan 10 '14 at 10:25

Proxying with Generics

1 Answers1