When Builders Aren't...

Question

Why do none of the FooBuilder classes implement javafx.util.Builder? In particular, I'm confused as to how to work with the FXMLLoader.setBuilderFactory() method. I would expect that give something like this:
public class MyLabelBuilderExt<B extends LabelBuilderExt<B>> extends LabelBuilder<B> {
    public LabelBuilderExt<B> styleClasses(String classes) {
        styleClass(Array.asList(classes.split(",")));
        return this;
public class BuilderFactoryExt implements BuilderFactory {
    private JavaFXBuilderFactory defaultFactory = new JavaFXBuilderFactory();
    @Override
    public Builder<?> getBuilder(Class<?> aClass) {
        if (Label.class.equals(aClass)) {
            return new MyLabelBuilderExt();
        return defaultFactory.getBuilder(aClass);
}then the following should work:
FXMLLoader loader = new FXMLLoader();
loader.setBuilderFactory(new BuilderFactoryExt());but obviously it fails, because MyLabelBuilderExt cannot be cast to Builder. Easy, just add the required implements clause, no other changes are needed as it already has all of the necessary methods, but it still fails when I try to use it in FXML as it says that the styleClasses property cannot be found.
Does anybody have an example of creating a custom builder and using it from FXML that they'd be willing to share?

Answer 1

Hi,
This issue is currently being tracked here:
http://javafx-jira.kenai.com/browse/RT-14875
Here's an example of a builder factory that produces Label builders. I used a similar example in my recent talk on FXML at JavaOne:
package examples.fxml.builder;
import javafx.fxml.JavaFXBuilderFactory;
import javafx.scene.control.Label;
import javafx.util.Builder;
import javafx.util.BuilderFactory;
public class ExampleBuilderFactory implements BuilderFactory {
    private JavaFXBuilderFactory defaultBuilderFactory = new JavaFXBuilderFactory();
    @Override
    public Builder<?> getBuilder(Class<?> type) {
        return (type == Label.class) ? new LabelBuilder() : defaultBuilderFactory.getBuilder(type);
package examples.fxml.builder;
import javafx.scene.control.Label;
import javafx.util.Builder;
public class LabelBuilder implements Builder<Label> {
    private String text = "";
    public String getText() {
        return text;
    public void setText(String text) {
        this.text = text;
    @Override
    public Label build() {
        Label label = new Label();
        label.setText(text);
        return label;
}Here's an example app you can use to test the builder factory:
package examples.fxml.builder;
import javafx.fxml.FXMLLoader;
import javafx.scene.control.Label;
public class BuilderExample {
    public static void main(String[] args) throws Exception {
        Label label = FXMLLoader.load(BuilderExample.class.getResource("builder_example.fxml"),
            null, new ExampleBuilderFactory());
        System.out.println(label.getText());
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.*?>
<Label text="Hello World!"/>Hope this helps,
Greg