On Fri, 14 Aug 2026 21:32:44 GMT, Andy Goryachev <[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/WeakReferenceWrapper.java > line 40: > >> 38: * In the case of a value object, the referent is never collected, so it >> is only >> 39: * suitable for uses that do not rely on the object being placed onto a >> reference >> 40: * queue. > > I might suggest to include the JBS number for when we need to undo / redo > things due to inevitable change in the value objects JEP (and possibly a link > to the JEP itself). > > Perhaps also say a couple of words about the fact that this class should not > exist had they decided to make the WeakReference implementation handle this > case transparently. There is no JBS issue or JEP that will eliminate the need for this. The restriction is intentional with no current plan to change it. I could add a comment that this class _might_ become unnecessary in the future, if a there is a change in the way `WeakReference` deals with value objects, but it is uncertain if or when that might be. > WeakReference(T) should work as before But that isn't the case. ------------- PR Review Comment: https://git.openjdk.org/jfx/pull/2250#discussion_r3787754994 PR Review Comment: https://git.openjdk.org/jfx/pull/2250#discussion_r3787751549
