java.nio.Path relativize between Paths does assumptions, which I cannot check

Question

I am using the new Path object of java 7 and I am running into an issue.

I have a file storage system with a base directory and I create my own relative path. In the end I want to store just this relative path somewhere. I am running into a problem with Path.relativize though.

I have two usecases. 1.

Path baseDir = Paths.get("uploads");
Path filename = Paths.get("uploads/image/test.png")

return baseDir.relativize(filename);

This returns a Path image/test.png , which is perfect.

However, usecase 2:

Path baseDir = Paths.get("uploads");
Path filename = Paths.get("image/test.png")

return baseDir.relativize(filename);

returns ../image/test.png . I just want it to return "image/test.png"

In the Path tutorial it says

In the absence of any other information, it is assumed that 2 Paths are siblings

What I want is to be able to detect that this is the case. In this case, I want to just return the filename and ignore the baseDir.

I currently solve it like this, but I was hoping there was a better way:

Path rootEnding = getRootDirectory().getName(getRootDirectory().getNameCount() - 1);

for (Path part : path) {
    if (part.equals(rootEnding)) {
        return getRootDirectory().relativize(path);
    }
}

return path;

So my question is, is there any better way of checking this?

Answer 1

Try adding a normalize() after relativize() . It seems to intended to do exactly this (remove unnecessary .. and . ). Don't miss the caution about symlinks in the javadoc.

Answer 2

This isn't 100% equivalent to what you wrote above, but I think it does what you want. Basically, let baseDir be a relative path. Pretend that whatever baseDir is relative to is the root of the file system. Then allow filename to be either relative or absolute from this "simulated root".

What about:

if (filename.startsWith(baseDir)) {
    filename = baseDir.relativize(filename);
}