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nio2

nio2: detect '..' and suchlike elements

I wish to use a string handed to me as a parameter as an element of a pathname. I do not wish to be troubled with 'Little Bobby Tables'. That is, I don't want '..' to be acceptable. I want this to work with an arbitrary NIO2 FileSystem, so just looking for the string .. isn't good enough. I can make some checks, such as !path.isAbsolute(), and path.getNameCount() == 1 to filter out other problem cases, but can I do anything other than pass it to resolve and look for the wrong name count to tell if it has the semantics of ..?

Solution

  • toRealPath()

    Is mostly the answer. The method on a path after resolved gives you the real path after resolving parent (e.g. "..") and links.

    You can then use root.startsWith( path ) to quickly check that it is in your subtree.

    But: Works only for existing files.