Proxying alreade created objects.

Question

With reflection Proxies can be created for defined interfaces. (using:
Foo f = (Foo) Proxy.newProxyInstance(Foo.class.getClassLoader(),
new Class[] { Foo.class },
handler);
Is it possible to create a proxy for already created objects?.
With that i mean for example: I have a instance of class Foo. Foo has one method bar(). When bar() is invoked on this particular instance of Foo I want the same behavior as with a Proxy/InvocationHandler with an invocation on the invoke() method on the InvocationHandler.

Answer 1

AFAIKS all you need to do is to create the a Invokation handler that passes all calls to your concrete class instance.
You might do something like
public Foo wrapFoo(final Foo concreteFoo) {
    return proxy.newProxyInstance(Foo.class.getClassLoader, new Class[]{Foo.class}, new InvocationHandler() {
    public Object invoke(Object proxy, Method method, Object[]args) throws Exception {
      try {
     // insert tracing code etc. here
       return method.invoke(concreteFoo, args);
          } catch (InvocationTargetExcepion e) {
             throw e.getCause();
  }Of course, Foo must be an interface.