How to read a file from JAR using NIO?

Question

Reading a file from the executable JAR file itself using ClassLoader.getResourceAsStream(...) is a known concept to me, but how would I do the same using Java NIO?

The target is to have a function as follows:

static String readFullyFromJar(String filename) {
    final Path path = Paths.get(Main.class.getResource(fileName).toURI());
    final byte[] bytes = Files.readAllBytes(path);
    return new String(bytes, CHARSET_ASCII);
}

While this works fine in the IDE, I get a

java.nio.file.FileSystemNotFoundException
    at com.sun.nio.zipfs.ZipFileSystemProvider.getFileSystem(ZipFileSystemProvider.java:171))

when I try this with the real JAR, even though the target file is in the correct place.

Answer 1

It turns out that my code above is actually correct, the issue is within Java itself.

According to this Bug ID , Java is not properly using the ZipFileSystemProvider as it should. Supposed to be fixed in Java 8. (My actual problem is described in this duplicate report )