On Thu, 6 Aug 2026 20:34:13 GMT, Kevin Rushforth <[email protected]> wrote:
> This PR creates a WeakReferenceWrapper object to replace direct uses of > WeakReference in controls where the referent is a user-supplied object of an > unknown type. > > As noted in JEP 401, which is now integrated into JDK 28, "The garbage > collection APIs in java.lang.ref ... do not allow developers to manually > manage value objects in the heap. Attempts to create Reference objects for > value objects throw IdentityException at run time." > > Several core JDK classes such as all of the primitive wrappers (e.g., > `Integer`, `Character`), `Optional`, `LocalDateTime`, and a few others are > now value types if JDK 28 is run with the `--enable-preview` option. > > The `ListView`, `ComboBox`, `TableView`, and `TreeTableView` controls take a > parameterized item type and hold items of that type. The following places in > the implementation create weak references to an item. If that item type is a > value class -- meaning that it does not have identity -- creating the > `WeakReference` fails. > > As noted in the JBS issue, there are 3 cases to consider. > > 1. `SelectedItemsReadOnlyObservableList<E>` -- `E` is the item type (created > by `MultipleSelectionModelBase<T>`) : `ListView`, `TableView`, `ComboBox` > (due to its skin creating a `ListView<T>`) -- replace with > `WeakReferenceWrapper` > > 2. `TablePosition<S,T>` -- `S` is the item type : `TableView` -- the > reference is unused, so I removed it > > 3. `TableCell<S,T>` and `TreeTableCell<S,T>` -- `S` is the item type : > `TableView`, `TreeTableView` -- replace with `WeakReferenceWrapper` > > The new `WeakReferenceWrapper` class takes a referent of any type and either > creates a WeakReference (if it has identity) or directly stores the reference > (if it is null or does not have identity). I added a test for the wrapper. > > All of the controls tests pass with this fix. I did three test runs as > follows: > > 1. JDK 25 > 2. JDK 28 without `--enable-preview` > 3. JDK 28 with `--enable-preview` > > Without the fix, 31 controls tests fails on the 3rd run. > > --------- > - [x] I confirm that I make this contribution in accordance with the [OpenJDK > Interim AI Policy](https://openjdk.org/legal/ai). modules/javafx.controls/src/main/java/com/sun/javafx/scene/control/SelectedItemsReadOnlyObservableList.java line 40: > 38: private final ObservableList<Integer> selectedIndices; > 39: private final Supplier<Integer> modelSizeSupplier; > 40: private final List<WeakReferenceWrapper<E>> itemsRefList; This is still confusing me as also mentioned in the ticket. For example, the `SelectionModel` has a `selectedItem` property, where we save the item `<T>`. So the item `T` is saved, without any `WeakReference` handling. And this is used in e.g. `ComboBox`, which does not seems to leak memory. So I wonder why we use a `WeakReference` here. The `WeakReference` usage in the `TableCell` is also questionable. Maybe worth to research in a follow-up? ------------- PR Review Comment: https://git.openjdk.org/jfx/pull/2250#discussion_r3797497715
