The copy of resolver.jar here is actually a slightly modified version of version 1.2
of Apache XML Commons Resolver. I believe it trips up on a bug in JDK 5 (apaprently
not found in 1.4 or 6) wherein java.net.URL.toString() returns an invalid URL
representation beginning with only "file://" instead of "file:/" or "file:///",
and when reparsed later into a URL in the code it yields an UnknownHostException,
which prevents the library from using DTDs stored on the local file system.
See http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6351751

My workaround is to add code before this line in CatalogResolver.resolveEntity():

	URL url = new URL(resolved);

Like so:

    if (resolved.startsWith("file://") &&
        !resolved.startsWith("file:///")) {
      resolved = "file:///" + resolved.substring(7);
    }

	URL url = new URL(resolved);


Also, if you are using Java 6 to compile for this project, the Ant build file resolver.xml
should be modified so that <javac> targets specify source="1.5" and target="1.5".


Finally we realized this library isn't designed to load resources from the classpath. A
little more hacking does it. In the same method,

    URL url = new URL(resolved);
	InputStream iStream = url.openStream();

Should change to:

	URL url = new URL(resolved);

	InputStream iStream = null;
	try {
	  iStream = url.openStream();
	} catch (FileNotFoundException fnfe) {
	  // also added by srowen
      // If file not available, look in classpath
      resolved = getResourceFromAbsoluteFilename(resolved);
      iStream = getClass().getResourceAsStream("/" + resolved);
    }

	...

	private static String getResourceFromAbsoluteFilename(final String systemId) throws MalformedURLException {
		// systemId is something like file:///foo/bar/dtd/stuff.dtd
		// This will generate something like file:///foo/bar/:
		final String baseFileName = FileURL.makeURL("").toString();
		// We need to pick out "dtd/stuff.dtd", but can't do it with a simple substring call.
		// There are issues with, for example, how many slashes follow the file: protocol
		final int systemIdSlashEnd = findEndOfSlashes(systemId);
		final int baseFileNameSlashEnd = findEndOfSlashes(baseFileName);
		final int prefixLength = baseFileName.length() - baseFileNameSlashEnd;
		return systemId.substring(systemIdSlashEnd + prefixLength);
	}

	private static int findEndOfSlashes(final String s) {
		int i = 0;
		while (s.charAt(i) != '/') {
			i++;
		}
		while (s.charAt(i) == '/') {
			i++;
		}
		return i;
	}

-srowen