code: public InvocationHandler getInvocationHandler(Object proxy) {
          Field field = getInvocationHandlerField();
          try {
              return (InvocationHandler) field.get(proxy);
          } catch (IllegalArgumentException e) {
              throw new RuntimeException("Object is not a proxy of correct type", e);
          } catch (IllegalAccessException e) {
              throw new RuntimeException(e);
          }
      }
docs: Returns the invocation handler for a proxy created from this factory.
  
  @param proxy the proxy
  @return the invocation handler