getResourceAsStream() returns null only when in jar file

Question

I know the same question has been asked many many times, but going through all the answers already posted I couldn't find a solution.

First of all here's the code I'm using to test the issue after i encountered it in my project :

InputStream test;

System.out.println(this.getClass());
System.out.println(("classpath is: " + System.getProperty("java.class.path")));

test = getClass().getResourceAsStream("/pairs/images/100/back/back1.png");

if (test == null)
{
    System.out.println("getClass().getResourceAsStream(\"/pairs/images/100/back/back1.png\") is null");
    test = GridPanel.class.getClassLoader().getResourceAsStream("pairs/images/100/back/back1.png");
}

if (test == null)
{
    System.out.println("GridPanel.class.getClassLoader().getResourceAsStream(\"pairs/images/100/back/back1.png\") is null");
    test = ClassLoader.getSystemClassLoader().getResourceAsStream("pairs/images/100/back/back1.png");
}

if (test == null)
{
    System.out.println("ClassLoader.getSystemClassLoader().getResourceAsStream(\"pairs/images/100/back/back1.png\") is null");
    Thread.currentThread().getContextClassLoader().getResourceAsStream("pairs/images/100/back/back1.png");
}

if (test == null)
    System.out.println("Thread.currentThread().getContextClassLoader().getResourceAsStream(\"pairs/images/100/back/back1.png\") is null");

So as per title everyone of these calls to getResourceAsStream() returns null, but only when executin the jar file, when launching inside the IDE (Netbeans 8.0.2) they all return the correct stream (tested individually not with this piece of code) and I can work with it.

The jar file contents are as follow:

While the src folder in the netbeans project folder is the following:

So I'm really baffled at the moment, I've tried using the default settings when building with netbeans but I'm losing my head around this issue.

Any hints or ideas would be much appreciated!

Answer 1

I think the getResourceAsStream is not reading from filesystem, the leading slash will try to read from the root of the classpath (if you add a directory will read from the root). If you don't put the leading slash, you will read from the package the class is from.

Did you add the directory/subdirectories you want to read the file from in the classpath?