Hi Peter,
Thanks for reviewing.
This is a transition step to removing the finalize method completely
while giving subclasses
notice to upgrade their cleanup activities and yet gain the performance
benefits sooner.
Later, finalize() and related compatibility mechanisms will be removed.
Simpler code, even if sometimes less than optimal is preferred to
maintain compatibility in the interim.
...
On 12/4/2017 9:25 AM, Peter Levart wrote:
Hi Roger,
On 12/04/2017 03:09 PM, Peter Levart wrote:
On 12/04/2017 02:25 PM, Peter Levart wrote:
Hi Rogger,
On 12/04/2017 02:17 PM, Peter Levart wrote:
Hi Rogger,
Interesting approach. Conditional finalization. You use
finalization to support cases where user overrides finalize()
and/or close() and Cleaner when he doesn't.
I wonder if it is the right thing to use AltFinalizer when user
overrides finalize() method. In that case the method is probably
not empty and calls super.finalize() (if it is empty or doesn't
call super, user probably doesn't want the finalization to close
the stream) and so normal finalization applies. If you register
AltFinalizer for such case, close() will be called twice.
Ah, scrap that. I forgot that XXXStream.finalize() is now empty, so
user overriding it and calling super does not in fact close the
stream. You have to register AltFinalizer in that case. But now I
wonder if the logic should still be 3-state and do the following:
- if user overrides finalize() - use AltFinalizer to call both:
first finalize() and then close(); else
- if user overrides close() - use AltFinalizer to call close(); else
- use Cleaner
What do you think?
Regards, Peter
I just realized that in the above case when finalize is overridden,
it would be called twice. once by finalization and once by
AltFinalizer. So your logic is as correct as it can be for that case
(to just call close() with AltFinalizer). The only problem is order
which is arbitrary, so it may happen that AltFinalizer calls close()
1st and then finalization calls overridden finalize() method which
might expect the stream to still be open until it calls
super.finalize().
Regards, Peter
Final refinement... (hopefully!)
If user overrides just finalize() and does not override close(), then
it might be best to employ Cleaner to close the stream. Cleaner is
Phantom based and will get fired after finalization invokes overridden
finalize(), enabling the finalize() method to still access the stream
in that case. So this is the final logic (I think):
- if user overrides close(), use AltFinalizer to call close(); else
- use Cleaner to close the stream
The above logic in action:
finalize() close() action
not overridden not overridden Cleaner closes stream
not overridden overridden AltFinalizer calls close()
overridden not overridden finalization calls
finalize() then Cleaner closes stream
overridden overridden finalization calls
finalize() and AltFinalizer calls close() (in arbitrary order)
Right, if close() is not overridden the behavior of close() is known and
the Cleaner can be used.
The contents of an overridden finalize() method are unknowable, it may
or may not call close() itself
and may or may not call super.finalize(). If close() is called, then
the Cleaner will be removed; otherwise it will release the resources.
The close method should be idempotent, calling it twice should not be a
problem.
This does simplify the logic.
Thanks, Roger
Regards, Peter
