I posted a reply on Github, but it's not making it to the list (that I
can see) for some reason.
--John
On 05/07/2022 19:18, Michael Strauß wrote:
On Fri, 1 Jul 2022 15:16:24 GMT, John Hendrikx <jhendr...@openjdk.org> wrote:
I have yet another question. The following test passes for `Bindings.select`,
but fails for `ObservableValue.flatMap`:
JMemoryBuddy.memoryTest(test -> {
class ValueHolder {
final StringProperty value = new SimpleStringProperty(this, "value");
StringProperty valueProperty() { return value; }
}
ObjectProperty<ValueHolder> valueHolderProperty = new
SimpleObjectProperty<>();
valueHolderProperty.set(new ValueHolder());
// Map the nested property value
ObservableValue<String> mapped =
valueHolderProperty.flatMap(ValueHolder::valueProperty);
// Note: the test passes when using the following alternative to flatMap:
// ObservableValue<String> mapped = Bindings.selectString(valueHolderProperty,
"value");
// Bind the mapped value to a property that will soon be GC'ed.
ObjectProperty<String> otherProperty = new SimpleObjectProperty<>();
otherProperty.bind(mapped);
test.setAsReferenced(valueHolderProperty);
test.assertCollectable(otherProperty);
test.assertCollectable(mapped); // expectation: the mapped value is
eligible for GC
});
My observation is that a flat-mapped value that was once observed is not
eligible for garbage-collection even when the observer itself is collected.
This seems to be quite unexpected to me, because it means that a bound property
that is collected without being manually unbound will cause a memory leak in
the mapped binding.
Is this by design? If so, I think this can lead to subtle and hard to diagnose
bugs, and should be documented at the very least.
-------------
PR: https://git.openjdk.org/jfx/pull/675
