Hi Eamonn,
Thanks for the comments and correction, the intention was to describe the
behavior consistently.
(I updated the webrev in place with the editorial changes).
Thanks, Roger
On 10/1/2015 11:11 AM, Eamonn McManus wrote:
I think this is a great idea. In addition to the NetBeans precedent
cited in the Issue, I'll note that Guava has
FinalizableReferenceQueue. Like the NetBeans solution, that has proved
tricky to make collectable in a context where its ClassLoader might
become otherwise unreferenced. Having the facility in the JRE obviates
that problem.
As a minor note, the javadoc says "phantomCleanup registers the
Runnable to be run when object is not phantom reachable", which I
don't think is technically accurate. The java.lang.ref definition of
reachability is that an object becomes (for example) phantom reachable
when it is referenced by a phantom reference but no longer has any
stronger level of reachability. So the text here should say "when the
object becomes phantom reachable". Likewise the per-method text "when
the object is unreachable by a PhantomReference" should say "becomes
phantom reachable". And of course the same, mutatis mutandis, for the
soft and weak equivalents.
Éamonn
2015-10-01 7:12 GMT-07:00 Roger Riggs <roger.ri...@oracle.com>:
Please review a proposal for public Cleaner API:
A Cleaner is proposed to provide an easy to use alternative to finalization.
The service would provide easy registration and cancellation of cleanup
functions for objects. Applications create a cleanup service for their own
use and the service terminates when it is no longer in use.
Finalization has a long history of issues both in usage and performance.
PhantomReferences have been proposed as the alternative GC based mechanism
for cleaning functions but it has been left as an exercise to the developer
to construct the necessary mechanisms to handle ReferenceQueues, handle
threading issues and robust termination.
The Cleaner performs cleaning functions when objects are unreachable as
found by garbage collection using the existing mechanisms of
PhantomReference, WeakReference, SoftReferences, and ReferenceQueues. It
manages a thread that dequeues references to unreachable objects and invokes
the corresponding cleaning function. Registered cleaning functions can be
cleared if no longer needed, can be invoked explicitly to perform the
cleanup immediately, or be invoked when the object is not reachable (as
detected by garbage collection) and handled by a cleanup thread.
The java.lang.ref package is proposed for the Cleaner because it is
complementary to the reference classes and reference queues and to make it
easy to find.
It is not a goal to replace all uses of finalization or sun.misc.Cleaner in
the JDK.
Investigation will evaluate if and in what cases the Cleaner can replace
finalization.
A subsequent task will examine uses of finalization and propose specific
changes
on a case by base basis.
Please review and comment:
Javadoc:
http://cr.openjdk.java.net/~rriggs/cleaner-doc/
Webrev:
http://cr.openjdk.java.net/~rriggs/webrev-cleaner-8138696/
Issue:
https://bugs.openjdk.java.net/browse/JDK-8138696
Thanks, Roger
