This is an implementation of the proposal in https://bugs.openjdk.java.net/browse/JDK-8274771 that me and Nir Lisker (@nlisker) have been working on. It's a complete implementation including good test coverage.
This was based on https://github.com/openjdk/jfx/pull/434 but with a smaller API footprint. Compared to the PoC this is lacking public API for subscriptions, and does not include `orElseGet` or the `conditionOn` conditional mapping. **Flexible Mappings** Map the contents of a property any way you like with `map`, or map nested properties with `flatMap`. **Lazy** The bindings created are lazy, which means they are always _invalid_ when not themselves observed. This allows for easier garbage collection (once the last observer is removed, a chain of bindings will stop observing their parents) and less listener management when dealing with nested properties. Furthermore, this allows inclusion of such bindings in classes such as `Node` without listeners being created when the binding itself is not used (this would allow for the inclusion of a `treeShowingProperty` in `Node` without creating excessive listeners, see this fix I did in an earlier PR: https://github.com/openjdk/jfx/pull/185) **Null Safe** The `map` and `flatMap` methods are skipped, similar to `java.util.Optional` when the value they would be mapping is `null`. This makes mapping nested properties with `flatMap` trivial as the `null` case does not need to be taken into account in a chain like this: `node.sceneProperty().flatMap(Scene::windowProperty).flatMap(Window::showingProperty)`. Instead a default can be provided with `orElse`. Some examples: void mapProperty() { // Standard JavaFX: label.textProperty().bind(Bindings.createStringBinding(() -> text.getValueSafe().toUpperCase(), text)); // Fluent: much more compact, no need to handle null label.textProperty().bind(text.map(String::toUpperCase)); } void calculateCharactersLeft() { // Standard JavaFX: label.textProperty().bind(text.length().negate().add(100).asString().concat(" characters left")); // Fluent: slightly more compact and more clear (no negate needed) label.textProperty().bind(text.orElse("").map(v -> 100 - v.length() + " characters left")); } void mapNestedValue() { // Standard JavaFX: label.textProperty().bind(Bindings.createStringBinding( () -> employee.get() == null ? "" : employee.get().getCompany() == null ? "" : employee.get().getCompany().getName(), employee )); // Fluent: no need to handle nulls everywhere label.textProperty().bind( employee.map(Employee::getCompany) .map(Company::getName) .orElse("") ); } void mapNestedProperty() { // Standard JavaFX: label.textProperty().bind( Bindings.when(Bindings.selectBoolean(label.sceneProperty(), "window", "showing")) .then("Visible") .otherwise("Not Visible") ); // Fluent: type safe label.textProperty().bind(label.sceneProperty() .flatMap(Scene::windowProperty) .flatMap(Window::showingProperty) .orElse(false) .map(showing -> showing ? "Visible" : "Not Visible") ); } Note that this is based on ideas in ReactFX and my own experiments in https://github.com/hjohn/hs.jfx.eventstream. I've come to the conclusion that this is much better directly integrated into JavaFX, and I'm hoping this proof of concept will be able to move such an effort forward. ------------- Commit messages: - Initial proposal Changes: https://git.openjdk.java.net/jfx/pull/675/files Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=675&range=00 Issue: https://bugs.openjdk.java.net/browse/JDK-8274771 Stats: 1501 lines in 11 files changed: 1498 ins; 0 del; 3 mod Patch: https://git.openjdk.java.net/jfx/pull/675.diff Fetch: git fetch https://git.openjdk.java.net/jfx pull/675/head:pull/675 PR: https://git.openjdk.java.net/jfx/pull/675
