Question

I have a servlet that needs to write out files that have a user-configurable name. I am trying to use URI encoding to properly escape special characters, but the JRE appears to automatically convert encoded forward slashes %2F into path separators.

Example:

File   dir = new File("C:\Documents and Setting\username\temp");
String fn  = "Top 1/2.pdf";
URI    uri = new URI( dir.toURI().toASCIIString() + URLEncoder.encoder( fn, "ASCII" ).toString() );
File   out = new File( uri );

System.out.println( dir.toURI().toASCIIString() );
System.out.println( URLEncoder.encode( fn, "ASCII" ).toString() );
System.out.println( uri.toASCIIString() );
System.out.println( output.toURI().toASCIIString() );

The output is:

file:/C:/Documents%20and%20Settings/username/temp/
Top+1%2F2.pdf   
file:/C:/Documents%20and%20Settings/username/temp/Top+1%2F2.pdf
file:/C:/Documents%20and%20Settings/username/temp/Top+1/2.pdf

After the new File object is instantiated, the %2F sequence is automatically converted to a forward slash and I end up with an incorrect path. Does anybody know the proper way to approach this issue?

The core of the problem seems to be that

uri.equals( new File(uri).toURI() ) == FALSE

when there is a %2F in the URI.

I’m planning to just use the URLEncoded string verbatim rather than trying to use the File(uri) constructor.

Answer 1

The new File(URI) constructs the file based on the path as obtained by URI#getPath() instead of -what you expected- URI#getRawPath(). This look like a feature “by design”.

You have 2 options:

1. Run URLEncoder#encode() on fn twice (note: encode(), not encoder()).
2. Use new File(String) instead.