Tomer Gabel's annoying spot on the 'net RSS 2.0
# Monday, August 3, 2009

Apparently Java has quite a few known but practically undocumented issues with its handling of UNC paths under Windows. I’ve specifically encountered this bug albeit in a slightly different scenario:

public void test() throws URISyntaxException {
final URI uri = new URI( "file://c:/temp/test/ham.and.eggs" );
new File( uri ); // IllegalArgumentException thrown here

Apparently the two slashes after file: are misinterpreted as the authority part of the URI; this thread on StackOverflow may give a few starting points if want to delve deeper. It seems Java implements an older RFC for URIs which has slightly different tokenization rules.
At any rate, so far the only sensible solution I’ve managed to come with is to manually remove or add (depending on your tastes…) a slash:

* Resolves the specified URI, and returns the file
* represented by the URI.
* @param uri The URI for which to return an absolute path.
* @return The {@link File} instance represented by the
* specified URI.
* @throws IllegalArgumentException <ul><li>The URI cannot
* be null.</li><li>Wrong URI scheme for path resolution;
* only file:// URIs are supported.</li></ul>
public static File getFile( URI uri )
throws IllegalArgumentException {
if ( uri == null )
throw new IllegalArgumentException(
"The URI cannot be null." );

if ( !"file".equals( uri.getScheme() ) )
throw new IllegalArgumentException( "Wrong URI " +
"scheme for path resolution, expected \"file\" " +
"and got \"" + uri.getScheme() + "\"" );

// Workaround for the following bug:
// Remove extra slashes after the scheme part.
if ( uri.getAuthority() != null )
try {
uri = new URI( uri.toString().replace(
"file://", "file:/" ) );
} catch ( URISyntaxException e ) {
throw new IllegalArgumentException( "The specified " +
"URI contains an authority, but could not be " +
"normalized.", e );

return new File( uri );

This is definitely a workaround, but according to newsgroup and forum posts these bugs have been around forever. If anyone has a more elegant solution I’d love to know.
Monday, August 3, 2009 7:00:20 AM (Jerusalem Standard Time, UTC+02:00)  #    -
Development | Java
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