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

[Lance Andersen]

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> 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/
> 
> Javadoc:
>   http://cr.openjdk.java.net/~rriggs/cleaner-doc/index.html
> 
> Thanks, Roger
> 
> 
> On 11/23/2015 5:32 PM, 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:
>>> 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/
>>> 
>>> Updated Webrev:
>>>     http://cr.openjdk.java.net/~rriggs/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
> 



Lance Andersen| Principal Member of Technical Staff | +1.781.442.2037
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