[FIXED] Copy external resource files after building JavaFX app with Maven

Issue

Our JavaFX application is built with mvn clean javafx:jlink to create a standalone package for distribution. Now I need to include external resources (by that I mean config/content files in JSON that are not packaged into the application but reside outside in a freely accessible folder structure) into that bundle, preferably within the build process with maven.

So I would like to achieve the following: Copy MyProject/res/* to MyProject/target/MyProject/res

Many solutions I've found use the maven resources plugin and I tried the following to no avail:

<plugin>
            <artifactId>maven-resources-plugin</artifactId>
            <version>3.3.0</version>
            <executions>
                <execution>
                    <id>copy-external-resources</id>
                    <phase>generate-sources</phase>
                    <goals>
                        <goal>copy-resources</goal>
                    </goals>
                    <configuration>
                        <outputDirectory>${basedir}/target/res</outputDirectory>
                        <resources>
                            <resource>
                                <directory>res</directory>
                            </resource>
                        </resources>
                    </configuration>
                </execution>
            </executions>
        </plugin>

I know the path itself (/target/res) isn't necessarily right since I want it in the MyProject folder, but either way, no folder is copied at all. What am I doing wrong here? Please note that I'm not too familiar with Maven and it's phases and different stages.

This is how it's supposed to look like:

The red path is what's supposed to be copied to the target folder after build.

Solution

As suggested in the comments, one strategy for this is to use a "known location" (typically somewhere in the hierarchy under the user's home directory) for the file. Keep a default version of the file as a resource in the application bundle. At startup, check if the file exists in the expected location, and if not, copy the contents from the resource.

Here is a complete example. Note this will generate a folder (.configApp) in your home directory, and a file (config.properties) inside that folder. For convenience, pressing "OK" in the dialog on exit will remove these artifacts. You probably don't want this in production, so press "Cancel" to see how it works, and run it again and press "OK" to keep your filesystem clean.

package org.jamesd.examples.config;

import javafx.application.Application;
import javafx.application.Platform;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Button;
import javafx.scene.control.ButtonType;
import javafx.scene.control.Label;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Properties;

public class ConfigExample extends Application {

    private static final Path CONFIG_LOCATION
            = Paths.get(System.getProperty("user.home"), ".configApp", "config.properties");

    private Properties readConfig() throws IOException {
        if (!Files.exists(CONFIG_LOCATION)) {
            Files.createDirectories(CONFIG_LOCATION.getParent());
            Files.copy(getClass().getResourceAsStream("config.properties"), CONFIG_LOCATION);
        }
        Properties config = new Properties();
        config.load(Files.newBufferedReader(CONFIG_LOCATION));
        return config ;
    }
    
    @Override
    public void start(Stage stage) throws IOException {
        Properties config = readConfig();
        Label greeting = new Label(config.getProperty("greeting"));
        Button exit = new Button("Exit");
        exit.setOnAction(e -> Platform.exit());
        VBox root = new VBox(10, greeting, exit);
        root.setAlignment(Pos.CENTER);
        root.setPadding(new Insets(20));
        Scene scene = new Scene(root);
        stage.setScene(scene);
        stage.show();
    }

    @Override
    // Provide option for cleanup. Probably don't want this for production.
    public void stop() {
        Alert confirmation = new Alert(Alert.AlertType.CONFIRMATION, "Delete configuration after exit?");
        confirmation.showAndWait().ifPresent(response -> {
            if (response == ButtonType.OK) {
                try {
                    Files.delete(CONFIG_LOCATION);
                    Files.delete(CONFIG_LOCATION.getParent());
                } catch (IOException exc) {
                    exc.printStackTrace();
                }
            }
        });
    }


    public static void main(String[] args) {
        launch();
    }
}

with config.properties under src/main/resources and in the same package as the application class:

greeting=Hello

Answered By - James_D
Answer Checked By - David Goodson (JavaFixing Volunteer)