ADDITIONAL SYSTEM INFORMATION :
Windows 10 / JDK 17 ea 31 / openjfx-17-ea+15/ Open JDK 64 Bit Server VM (build 17-ea+31-2664, mixed mode, sharing)

A DESCRIPTION OF THE PROBLEM :
In Windows 10 with JDK 17-ea+15 but also with others JDK from 8 to 17 when i call the Method showPrintDialog in the Class PrinterJob in package package javafx.print is not working.
Dialog will not appear but the returned boolean is always true.
Reason is a flag headless (java.awt.headless) which in Spring is true initialized.
In the Implementation in Java Class J2DPrinterJob we have:

    public boolean showPrintDialog(Window owner) {

        if (jobRunning || jobDone) {
            return false;
        }

        if (GraphicsEnvironment.isHeadless()) {
            return true;
        }

Returning true to the call of the method showPrintDialog and not printing the dialog if the application is headless.

In my Opinion the bug should be repair just with a return false, because if i run the application with a headless modus and call the showPrintdialog it should not be possible and not return a true.

Or at least throw an Exception.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Create a Springboot Project in https://start.spring.io/ with maven, java and packaging jar. Version doesnt matter.
2. Change pom to include a JavaFX project.

<dependency>
            <groupId>org.openjfx</groupId>
            <artifactId>javafx-controls</artifactId>
            <version>17-ea+15</version>
        </dependency>

and under plugin

<plugin>
                <groupId>org.openjfx</groupId>
                <artifactId>javafx-maven-plugin</artifactId>
                <version>0.0.6</version>
                <executions>
                    <execution>
                        <!-- Default configuration for running -->
                        <!-- Usage: mvn clean javafx:run -->
                        <id>default-cli</id>
                        <configuration>
                            <mainClass>com.example.javafxprintdialog.JavafxprintdialogApplication</mainClass>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

3. In der Main Class, overried the start method with the next Snip:

package com.example.javafxprintdialog;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import javafx.application.Application;
import javafx.application.Platform;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.print.PrinterJob;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextArea;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

@SpringBootApplication
public class JavafxprintdialogApplication extends Application {

    private Label jobStatus;

    @Autowired
    public JavafxprintdialogApplication() {
        this.jobStatus = new Label();
    }

    public static void main(String[] args) {
        SpringApplication.run(JavafxprintdialogApplication.class, args);
        Application.launch(args);

    }

    @Override
    public void start(final Stage stage) {
        // Create the Text Label
        Label textLabel = new Label("Please insert your Text:");

        // Create the TextArea
        final TextArea textArea = new TextArea();

        // Create the Buttons
        Button pageSetupButton = new Button("Page Setup and Print");

        // Create the Event-Handlers for the Button
        pageSetupButton.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent event) {

                pageSetup(textArea, stage);
            }
        });

        // Create the Status Box
        HBox jobStatusBox = new HBox(5, new Label("Job Status: "), jobStatus);
        // Create the Button Box
        HBox buttonBox = new HBox(pageSetupButton);

        // Create the VBox
        VBox root = new VBox(5);

        // Add the Children to the VBox
        root.getChildren().addAll(textLabel, textArea, buttonBox, jobStatusBox);
        // Set the Size of the VBox
        root.setPrefSize(400, 300);

        // Set the Style-properties of the VBox
        root.setStyle("-fx-padding: 10;" +
            "-fx-border-style: solid inside;" +
            "-fx-border-width: 2;" +
            "-fx-border-insets: 5;" +
            "-fx-border-radius: 5;" +
            "-fx-border-color: #ffffff;");

        // Create the Scene
        Scene scene = new Scene(root);
        // Add the scene to the Stage
        stage.setScene(scene);
        // Set the title of the Stage
        stage.setTitle("A Printing Dialog Example");
        // Display the Stage
        stage.show();
    }

    private void pageSetup(Node node, Stage owner) {
        // Create the PrinterJob
        PrinterJob job = PrinterJob.createPrinterJob();

        if (job == null) {
            return;
        }

        // Show the page setup dialog
        Platform.runLater(() -> showpagesetupdialog(node, owner, job));
    }

    private void showpagesetupdialog(Node node, Stage owner, PrinterJob job) {
        System.out.println("Printer:" + job.getPrinter().toString());
        System.out.println("Settings:" + job.getJobSettings().toString());
        boolean proceed = job.showPageSetupDialog(owner.getScene().getWindow());

        if (proceed) {
            print(job, node);
        }
    }

    private void print(PrinterJob job, Node node) {
        // Set the Job Status Message
        jobStatus.textProperty().bind(job.jobStatusProperty().asString());

        // Print the node
        boolean printed = job.printPage(node);

        if (printed) {
            job.endJob();
        }
    }
}

4. run mvn clean install javafx:run


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
boolean should be false if the showPrintDialog doesnt appear.
ACTUAL -
boolean result of the method showPrintDialog is true but the Dialog is not appearing.

---------- BEGIN SOURCE ----------
package com.example.javafxprintdialog;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import javafx.application.Application;
import javafx.application.Platform;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.print.PrinterJob;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextArea;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

@SpringBootApplication
public class JavafxprintdialogApplication extends Application {

    private Label jobStatus;

    @Autowired
    public JavafxprintdialogApplication() {
        this.jobStatus = new Label();
    }

    public static void main(String[] args) {
        SpringApplication.run(JavafxprintdialogApplication.class, args);
        Application.launch(args);

    }

    @Override
    public void start(final Stage stage) {
        // Create the Text Label
        Label textLabel = new Label("Please insert your Text:");

        // Create the TextArea
        final TextArea textArea = new TextArea();

        // Create the Buttons
        Button pageSetupButton = new Button("Page Setup and Print");

        // Create the Event-Handlers for the Button
        pageSetupButton.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent event) {

                pageSetup(textArea, stage);
            }
        });

        // Create the Status Box
        HBox jobStatusBox = new HBox(5, new Label("Job Status: "), jobStatus);
        // Create the Button Box
        HBox buttonBox = new HBox(pageSetupButton);

        // Create the VBox
        VBox root = new VBox(5);

        // Add the Children to the VBox
        root.getChildren().addAll(textLabel, textArea, buttonBox, jobStatusBox);
        // Set the Size of the VBox
        root.setPrefSize(400, 300);

        // Set the Style-properties of the VBox
        root.setStyle("-fx-padding: 10;" +
            "-fx-border-style: solid inside;" +
            "-fx-border-width: 2;" +
            "-fx-border-insets: 5;" +
            "-fx-border-radius: 5;" +
            "-fx-border-color: #ffffff;");

        // Create the Scene
        Scene scene = new Scene(root);
        // Add the scene to the Stage
        stage.setScene(scene);
        // Set the title of the Stage
        stage.setTitle("A Printing Dialog Example");
        // Display the Stage
        stage.show();
    }

    private void pageSetup(Node node, Stage owner) {
        // Create the PrinterJob
        PrinterJob job = PrinterJob.createPrinterJob();

        if (job == null) {
            return;
        }

        // Show the page setup dialog
        Platform.runLater(() -> showpagesetupdialog(node, owner, job));
    }

    private void showpagesetupdialog(Node node, Stage owner, PrinterJob job) {
        System.out.println("Printer:" + job.getPrinter().toString());
        System.out.println("Settings:" + job.getJobSettings().toString());
        boolean proceed = job.showPageSetupDialog(owner.getScene().getWindow());

        if (proceed) {
            print(job, node);
        }
    }

    private void print(PrinterJob job, Node node) {
        // Set the Job Status Message
        jobStatus.textProperty().bind(job.jobStatusProperty().asString());

        // Print the node
        boolean printed = job.printPage(node);

        if (printed) {
            job.endJob();
        }
    }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Setting the default headless to false in Spring with:
SpringApplicationBuilder builder = new SpringApplicationBuilder(App.class);
        builder.headless(false).run(args);
will show the dialog

FREQUENCY : always