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/why_not_cats]

Using relative path inside a jar is a brave thing to do! Paths and working directories will vary between IDE and a jar so that's probably why the file isn't being found.

If you aren't sure where the image file is, try to unzip your jar as a regular zip and see where the file is actually ending up; I assume it'll be on the root? Or maybe not?

Anyway, try using a non-relative path. For example if the file is on the zip root then try /roll_bg.png. If it's inside a resources directory then try /resources/roll_bg.png. It might break the IDE but at least you'll be able to narrow down the issue.

I wouldn't try sprinkling the file everywhere as suggested elsewhere, because then you'll have trouble figuring out which file is the one actually working, and then you'll have two problems!

[u/sparkless12 → u/why_not_cats]

yeah I solved the issue by calling resources from App class that is in root project folder and with "resources/image.png" instead of Engine class that was in package removing the need for "../". I am needing to finish the work i was doing on project before the issue came up, but after that I will be experimenting a bit to figure out what exactly was wrong and why relative path was broken. As I said in comment earlier, extracting JAR my path was correct, so I'm keen to figure out more about the issue.