Hi Roger,
Just one thing about implementation:
Since the type exposed to user is Cleaner.Cleanable that has only a
single method clean(), it would be good if the implementation class
(CleanerImpl.PhantomCleanableRef) overrode
CleanerImpl.PhantomCleanable.clear() method and threw
UnsupportedOperationException, otherwise users will be tempted to cast
the returned Cleaner.Cleanable to Reference and invoke clear() method to
de-register cleanup action without invoking it. This is the only
remaining public Reference method that is not disabled this way.
Regards, Peter
On 12/09/2015 07:40 PM, Roger Riggs wrote:
Hi,
The example is revised to caution about inner classes and lambdas.
[1]http://cr.openjdk.java.net/~rriggs/webrev-cleaner-8138696/
[2]http://cr.openjdk.java.net/~rriggs/cleaner-doc/index.html
Thanks, Roger
On 12/9/2015 11:04 AM, Peter Levart wrote:
Hi Chris,
On 12/09/2015 04:03 PM, Chris Hegarty wrote:
Peter,
On 09/12/15 07:05, Peter Levart wrote:
Hi,
I think the only way to try to prevent such things is with a good
example in javadoc that "screams" of possible miss-usages.
public static class CleanerExample implements AutoCloseable {
private static final Cleaner cleaner = ...; // preferably a
shared cleaner
private final PrivateNativeResource pnr;
private final Cleaner.Cleanable cleanable;
public CleanerExample(args, ...) {
// prepare captured state as local vars...
PrivateNativeResource _pnr = ...;
this.cleanable = cleaner.register(this, () -> {
// DON'T capture any instance fields with lambda
since
that would
// capture 'this' and prevent it from becoming
I assume that the WARNING should include anonymous inner classes too
( which I expect are quite common, though less now with lambda ) ?
Is "leaking" 'this' in a constructor a potential issue with respect
to the visibility of pnr? As well as causing red-squiggly lines in
the IDE ;-)
'this' only leaks to the 'referent' field of PhantomReference where
by definition is not accessible.
'this' can become phantom-reachable before CleanerExample constructor
ends. But this is harmless, because the code that may execute at that
time does not access the object any more, so the object may be safely
collected.
Cleanup action can run at any time after registration even before
CleanerExample constructor ends. But this is harmless too, because it
only accesses PrivateNativeResource which is fully constructed before
registration of cleanup action.
I see no issues apart from IDE(s) not seeing no issues.
Regards, Peter
-Chris.
phantom-reachable!!!
_pnr.close();
});
this.pnr = _pnr;
}
public void close() {
cleanable.clean();
}
Regards, Peter
