Converting URLs to Files

Converting a File to a URL is difficult across different versions of Java; and across different platforms is tough.

File	URL
file.txt	file:file.txt
/Users	file:/Users
C:	file:///C:/
C:Users	file:///C:/Users
C:direct with a spacefile.txt	file://C:/directory%20with%20a%20space/file.txt
\host.orgsharedirectoryfile.txt	file://///host.org/share/directory/file.txt
/Users/Jody/java	file:///Users/Jody/java/

org.geotools.util.URLs in gt-metadata provides methods to centralise the handling of platform eccentricities, and ensure the correct encoding and decoding of characters such as spaces that are permitted in file paths but not in URLs. Use them wherever possible.

URLs.fileToUrl

Here is how to create a URL for a File in GeoTools:

URL url = URLs.fileToUrl(file);

The official Java 6 way to do this is to use:

URL url = file.toURI().toURL(); // can produce problems on Mac OSX

The traditional Java 1.4 way is now deprecated:

URL url = file.toURL(); // will produce invalid URL if spaces are in the path

URLs.urlToFile

When presented with a URL it is hard to know what to do - since we cannot know how a user has constructed the URL. So we have to assume the worst and try every possible way to untangle the provided URL.

We have spent a lot of time trying to package up a nice clean way of doing this for our code:

File f = URLs.urlToFile(url);

An early workaround for Java 1.4 code was to use the file authority information (to account for drive letters like “C:” and “D:”). If you find any of this code please update it to use URLs.urlToFile(url).:

File f = url.getAuthority() == null ?
            new File( url.getPath() ) :
            new File("//" + url.getAuthority() + url.getPath());