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 >
