How to use Files.getFileStore() for substed drive (on Windows)?

Question

When invoking Files.getFileStore() on a substed drive (on Windows), this results in following error:

The directory is not a subdirectory of the root directory

For example with:

subst P: C:\temp

running:

public static void main(String[] args) throws IOException {
    final Path dir = Paths.get("P:/sub");
    final FileStore fileStore = Files.getFileStore(dir);
    fileStore.isReadOnly();
}

results in:

Exception in thread "main" java.nio.file.FileSystemException: P:\sub: The directory is not a subdirectory of the root directory.

    at sun.nio.fs.WindowsException.translateToIOException(WindowsException.java:86)
    at sun.nio.fs.WindowsException.rethrowAsIOException(WindowsException.java:97)
    at sun.nio.fs.WindowsException.rethrowAsIOException(WindowsException.java:102)
    at sun.nio.fs.WindowsFileStore.create(WindowsFileStore.java:92)
    at sun.nio.fs.WindowsFileSystemProvider.getFileStore(WindowsFileSystemProvider.java:482)
    at java.nio.file.Files.getFileStore(Files.java:1411)
    at utils.FileStoreMain.main(FileStoreMain.java:16)

How to fix this problem and receive the appropriate FileStore for P:?

Answer 1

Have a look at this bug report JDK-8034057 and at a related answer from Alan Bateman.

Answer 2

The problem is that a "substed drive" is not a file store; it just associates a drive letter with a path on an existing drive.

You did:

subst p: c:\temp

which means, in fact, that the real filestore of your p:\sub is the drive associated with c:.

Note: that's just a hypothesis, I don't actually run windows. But if you try and iterate over the filestores (ie, by calling .getFileSystem().getFileStores() on your Path instance) then P: will not appear.

Now, the question remains as to how to obtain the real filestore, if it's possible at all. Maybe a FileAttributeView exists which can provide you with this information; try and see what attribute views are available to you, and their parameters, by using this code:

// using some Path instance named path...
final FileSystem fs = path.getFileSystem();
final Set<String> viewNames = fs.supportedFileAttributesView();

for (final String viewName: viewNames) {
    System.out.println("View " + viewName + ':');
    System.out.println(Files.readAttributes(path, viewName + ":*"));
}

Maybe there exists a view with the information you are looking for... No guarantee though.