Is there a cross-platform Java method to remove filename special chars?

user_68507 0
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I'm making a cross-platform application that renames files based on data retrieved online. I'd like to sanitize the Strings I took from a web API for the current platform.

I know that different platforms have different file-name requirements, so I was wondering if there's a cross-platform way to do this?

Edit: On Windows platforms you cannot have a question mark '?' in a file name, whereas in Linux, you can. The file names may contain such characters and I would like for the platforms that support those characters to keep them, but otherwise, strip them out.

Also, I would prefer a standard Java solution that doesn't require third-party libraries.

filenames filesystems cross-platform java
8 Answers

It is not clear from your question, but since you are planning to accept pathnames from a web form (?) you probably ought block attempts renaming certain things; e.g. "C:\Program Files". This implies that you need to canonicalize the pathnames to eliminate "." and ".." before you make your access checks.

Given that, I wouldn't attempt to remove illegal characters. Instead, I'd use "new File(str).getCanonicalFile()" to produce the canonical paths, next check that they satisfy your sandboxing restrictions, and finally use "File.exists()", "File.isFile()", etc to check that the source and destination are kosher, and are not the same file system object. I'd deal with illegal characters by attempting to do the operations and catching the exceptions.

user_1399850

Paths.get(...) throws a detailed exception with the position of the illegal character.

public static String removeInvalidChars(final String fileName)
{
  try
  {
    Paths.get(fileName);
    return fileName;
  }
  catch (final InvalidPathException e)
  {
    if (e.getInput() != null && e.getInput().length() > 0 && e.getIndex() >= 0)
    {
      final StringBuilder stringBuilder = new StringBuilder(e.getInput());
      stringBuilder.deleteCharAt(e.getIndex());
      return removeInvalidChars(stringBuilder.toString());
    }
    throw e;
  }
}
user_4025170
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