Java：无法弄清楚如何使用class.getClassLoader（）。getResourceAsStream（），因此在构建工件时可以使用

Question

I have been tasked with developing a discord bot for a friend of mine and need to load some strings from a file. Now, to make this work when i export the project into a jar, someone told me to use class.getClassLoader().getResourceAsStream()

After fiddling around for 2 hours, reading documentation and asking again, i got it to work in intelliJ. It still does not work when i build the project though.

Project Structure My Code:

static final ArrayList<String> QUOTES = new ArrayList<>();

public static void loadArray() {
    try{
        //File fin = new File("src/main/java/com/github/MarvelousAdain/Quotes");
        //FileInputStream fis = new FileInputStream(fin);
        System.out.println("Called loadArray Method");
        BufferedReader br = new BufferedReader(new InputStreamReader(Utilities.class.getClassLoader().getResourceAsStream("Quotes")));

        String line;
        while ((line = br.readLine()) != null) {
            QUOTES.add(line);
        }
        System.out.println("Quotes loaded, no Problem.");
        br.close();
    }catch(IOException e){e.printStackTrace();}
}

If i try running my code in the jar, this throws a NullPointerException.

Stacktrace:

Exception in thread "main" java.lang.NullPointerException
    at java.io.Reader.<init>(Unknown Source)
    at java.io.InputStreamReader.<init>(Unknown Source)
    at com.github.MarvelousAdain.Utilities.loadArray(Utilities.java:31)
    at com.github.MarvelousAdain.Main.main(Main.java:18)

Help would be greatly appreciated.

Answer 1

Is the tool that creates the jar including the resource?

You can check with

jar tf myjar.jar

Or indeed, your favourite zip tool.

Peculiarly getResourceAsStream() returns null instead of throwing some kind of IOException like a normal API would.

Also note that ClassLoader.getResourceAsStream will take the name relative to the classpath, but Class.getResourceAsStream will modify the path using the name of the package of the specified class (ie in the same "directory" as the .class file).

Answer 2

So, this might be more of a work around, but it was the only way i got it to work right now. If someone has a better idea, which i'm sure someone has, then i'd still like to hear it.

I built the jar, opened it with winrar and put the 3 files that i want to read in there. It worked. If i put them in the same place within the IDE, it did not. I have no idea how/why this is the case, but for now this works for me. I'll update this if i find something better!