Cleanup URIUtil.toURI() for windows, document rationale behind each decision.

Author: joakime

jetty-core/jetty-util/src/main/java/org/eclipse/jetty/util/URIUtil.java

@@ -1932,7 +1932,21 @@ public static URI toURI(String reference)
              */
             URI uri = URI.create(reference);
             if (uri.isAbsolute())
-                return uri;
+            {
+                // At this point we have a string detected as a URI.
+                // But that could also include Windows paths like "C:\path\to\foo.jar" or "C:/path/to/foo.jar"
+                String scheme = uri.getScheme();
+                if (scheme.length() == 1 && Character.isLetter(scheme.charAt(0)))
+                {
+                    // Single character schemes are assumed to be windows.
+                    // Make it a file: URI and process it separately.
+                    return toURI("file:///" + uri.toASCIIString());
+                }
+                {
+                    // Anything else, scheme wise, is acceptable.
+                    return uri;
+                }
+            }
             if (LOG.isDebugEnabled())
                 LOG.debug("Input string is detected as a non-absolute URI \"{}\"", reference);
             throw new IllegalArgumentException("Non-absolute URI reference strings not supported");