[cap-talk] David Wagner's Google techtalk is now up!

[Mike Samuel]

On 12/12/2007, David Wagner <daw at cs.berkeley.edu> wrote:
>
> Mike Samuel <mikesamuel at gmail.com> writes:
> >Does Joe-E provide a tamed equivalent to
> >java.lang.reflect.Proxy.newProxyInstance?
>
> Yes: org.joe_e.reflect.Proxies.proxy().
>
> >If it does, then having access to an interface's class object allows you
> to
> >proxy that interface.
>
> In Joe-E, Class objects are ambiently available and therefore must


Public classes, and classes within the same package are ambiently available,
but you contradict a lot of people's assumptions if you make private inner
classes ambiently available.




not (and do not) convey authority.  For instance, you can always write
>   Class c = Foo.class;
> to get a Class object for class Foo.
>
> By the way, you don't need reflection to proxy an interface.  If you
> know statically what interface you want to proxy and how you want to
> handle all method calls to that interface, you can just write a class
> that implements that interface, and Bob's your uncle.


Not true.  Proxying allows you to do things with private inner classes and
package private classes that you can't do statically.  See the below
program.

import java.lang.reflect.*;

public class Foo {
  public static void main(String[] args) {
    Object baz = Proxy.newProxyInstance(
        Foo.class.getClassLoader(),
        new Class[] { Bar.c },
        new InvocationHandler() {
          public Object invoke(
              Object proxy, Method method, Object[] args) {
            System.err.println("Invoked " + method);
            return null;
          }
        });
    Bar.exec(baz);
  }
}

class Bar {
  // Class is private
  private interface Baz {
    void foo();
  }

  // but class object is exposed, either as a class, or because
  // Bar passes out an instance whose class is available via
  // getClass()
  static Class c = Baz.class;

  // The enclosing class unwraps an instance and assumes only
  // it could have created it.
  static void exec(Object o) {
    ((Baz) o).foo();
  }
}





This may be an obscure tangent; if so, my apologies....
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