getResourceAsStream() == null when run from JAR

[u/sparkless12]

hello!

I have line of code such as this:

final Image roll_bg = new Image(this.getClass().getResourceAsStream("../resources/roll_bg.png"));

in IDE image is found and is rendered on canvas as expected, when exported to JAR, run ends with error. For JAR runs then, I did most hacky thing possible to extract what is wrong like so:

URL path = App.class.getResource("App.class");
if (path.toString().contains("jar")) {
    PrintStream ps = new PrintStream("./log.txt");
    System.setErr(ps);
    System.setOut(ps);
    System.out.println("Stream OUT: rerouted!");
    System.err.println("Stream ERR: rerouted!");
}

and log.txt says that InputStream is null (presumably did not found resource)

Caused by: java.lang.NullPointerException: Input stream must not be null
    at javafx.graphics/javafx.scene.image.Image.validateInputStream(Unknown Source)
    at javafx.graphics/javafx.scene.image.Image.<init>(Unknown Source)
    at com.engine.Engine.<init>(Engine.java:32)
    at com.engine.Engine.get(Engine.java:94)
    at com.App.start(App.java:60)

most online resources point to this method being able to reach resources from within JAR, does not work for me though. Thank you for any help offered!

[u/morhp]

Does the jar file contain the roll_bg.png in the right directory? (You can open it by changing the extension to .zip). If not, there's probably a problem with how you create the jar file. Unfortunately you haven't written anything about how you do that.

[u/wildjokers → u/morhp]

(You can open it by changing the extension to .zip).

Or just jar tvf YourJarName.jar from the command-line.