RFR 9: 8138696 : java.lang.ref.Cleaner - an easy to use alternative to finalization

[Roger Riggs]

Hi Lance,

Cleaner class level javadoc defines the behavior:

"Unless otherwise noted, passing a null argument to a constructor or 
method in any class or interface in this package will cause a 
NullPointerException to be thrown."

Roger


On 12/02/2015 04:09 PM, Lance Andersen wrote:
> Hi Roger,
>
> Should the javadocs in the Cleaner methods include NPE given they use 
> Objects.requireNonNull?
>
> Best
> Lance
> On Dec 2, 2015, at 3:23 PM, Roger Riggs <Roger.Riggs at oracle.com 
> <mailto:Roger.Riggs at oracle.com>> wrote:
>
>> Please review the java.lang.ref.Cleaner and tests following the 
>> recommendation to simplify the public
>> interface to support only phantom cleanup.
>>
>> Webrev:
>> http://cr.openjdk.java.net/~rriggs/webrev-cleaner-8138696/ 
>> <http://cr.openjdk.java.net/%7Erriggs/webrev-cleaner-8138696/>
>>
>> Javadoc:
>> http://cr.openjdk.java.net/~rriggs/cleaner-doc/index.html 
>> <http://cr.openjdk.java.net/%7Erriggs/cleaner-doc/index.html>
>>
>> Thanks, Roger
>>
>>
>> On 11/23/2015 5:32 PM, mark.reinhold at oracle.com 
>> <mailto:mark.reinhold at oracle.com> wrote:
>>> ( Finally getting back to this, after too many weeks of travel ... )
>>>
>>> 2015/10/20 11:28 -0700, roger.riggs at oracle.com 
>>> <mailto:roger.riggs at oracle.com>:
>>>> Sorry for the silence, JavaOne preparations and the availability of
>>>> folks who wanted to review have stretched things out.
>>>>
>>>> The Cleaner API was very simple and saw feature creep as the ideas for
>>>> how it might be used were explored.  There are concerns about
>>>> committing to supporting subclassable CleanableReferences in all
>>>> future JDK versions before there had been a chance to see how if they
>>>> would be useful and necessary to address the need to reduce the use of
>>>> finalization within the OpenJDK and beyond.
>>>>
>>>> ...
>>>>
>>>> Updated Javadoc:
>>>> http://cr.openjdk.java.net/~rriggs/cleaner-doc/ 
>>>> <http://cr.openjdk.java.net/%7Erriggs/cleaner-doc/>
>>>>
>>>> Updated Webrev:
>>>> http://cr.openjdk.java.net/~rriggs/webrev-cleaner-8138696/ 
>>>> <http://cr.openjdk.java.net/%7Erriggs/webrev-cleaner-8138696/>
>>> I'm very happy to see this API return to something like its original
>>> simple form, but I think it can be simplified even further.
>>>
>>> We have a very strong need for phantom-ref-based cleaners, so as to
>>> discourage people from relying upon flaky finalization. The arguments in
>>> support of the weak and soft forms have, by contrast, been rather weak
>>> (and soft?).  I don't think it's right to bake methods into a core API
>>> based on just a couple of hypothetical use cases.  I'd much rather see
>>> the Cleaner::{phantom,soft,weak}Cleanable methods reduced to a single
>>> register method,
>>>
>>>     Cleaner.Cleanable register(Object, Runnable);
>>>
>>> which would create the phantom form only.  If strong justification for
>>> the other forms arise then we can generalize this later, either to
>>> distinct register{Soft,Weak} methods or, perhaps, to a method that takes
>>> a type token.
>>>
>>> - Mark
>>
>
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> <http://oracle.com/us/design/oracle-email-sig-198324.gif>Lance 
> Andersen| Principal Member of Technical Staff | +1.781.442.2037
> Oracle Java Engineering
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