Cannot access Java resource when packaged in Mac app bundle

Question

I am accessing a Java resource to use in my JavaFX application..

URL resource = getClass().getClassLoader().getResource("/image.jpg");
File file = new File(resource.getFile());
if (!file.exists()) {
    throw new FileNotFoundException("No image: " + file)
}

Everything works fine and the resource is found when running as the Java application.

However, now I am bundling my JavaFX application in a native Mac app using zenjava's Maven plugin:

<plugin>
    <groupId>com.zenjava</groupId>
    <artifactId>javafx-maven-plugin</artifactId>
    <version>2.0</version>
    <configuration>
        <mainClass>
            com.seaniscool.foobar.FooBar
        </mainClass>
    </configuration>
</plugin>

I build with the native plugin using:

mvn clean jfx:native

Now, when I run the application by running the Mac .app file, this resource can no longer be resolved to a file. getResource returns this URL:

jar:file:/Projects/foobar/target/foobar.app/Contents/Java/foobar-jfx.jar!/image.jpg

But it cannot be found when used as a File path.

Answer 1

The URL in

URL resource = getClass().getClassLoader().getResource("/image.jpg");

is a uniform resource locator. In this case it locates the resource identified by /image.jp in a .jar file. Which, as it turns out, is a type of zip file.

jar:file:/Projects/foobar/target/foobar.app/Contents/Java/foobar-jfx.jar!/image.jpg

A zip entry is not a file, it's just a bunch of bytes that have some meaning to a zip file. If you want to get those bytes as an InputStream, inflated, you can simply call

InputStream inputStream = resource.openStream();

See the javadoc of URL#openStream().

Answer 2

You must use the fully qualified name meaning : /package1/package2/.../file-name not /file-name directly