Distinguish between relative and absolute resource paths

Absolute paths begin with a / character and are interpreted relatively to the
ClassLoader default resource path.

src/main/java/de/tudresden/inf/mci/brailleplot/configparser/JavaPropertiesConfigurationParser.java

@@ -152,15 +152,23 @@ public final class JavaPropertiesConfigurationParser extends ConfigurationParser
      */
     private void includeResources(final String fileList, final URL parentUrl) throws ConfigurationParsingException, ConfigurationValidationException {
         for (String s : fileList.split(",")) {
+            s = s.trim();
+            boolean isAbsolutePath = s.startsWith("/");
 
             URL newUrl = null;
-            try {
-                newUrl = new URL(parentUrl.getProtocol(), parentUrl.getHost(), UrlHelper.getPathString(parentUrl) + "/" + s.trim() + INCLUDE_FILE_EXTENSION);
-            } catch (MalformedURLException e) {
-                throw new ConfigurationParsingException("Could not generate URI", e);
+            // If the value begins with a "/", treat path as absolute path in resources
+            if (isAbsolutePath) {
+                newUrl = getClass().getClassLoader().getResource(s.substring(1) + INCLUDE_FILE_EXTENSION);
+                // else treat relative
+            } else {
+                try {
+                    newUrl = new URL(parentUrl.getProtocol(), parentUrl.getHost(), UrlHelper.getPathString(parentUrl) + "/" + s.trim() + INCLUDE_FILE_EXTENSION);
+                } catch (MalformedURLException e) {
+                    throw new ConfigurationParsingException("Could not create URL to relative resource", e);
+                }
             }
 
-            mLogger.debug("Prepare recursive parsing of properties file in the java resources at \"{}\"", newUrl);
+            mLogger.debug("Prepare recursive parsing of properties file in the java resources at \"{}\"", UrlHelper.getString(newUrl));
 
             try (InputStream is = newUrl.openStream()) {
                 parse(is, UrlHelper.getParentUrl(newUrl));

src/main/java/de/tudresden/inf/mci/brailleplot/util/UrlHelper.java

@@ -26,6 +26,10 @@ public final class UrlHelper {
         return URLDecoder.decode(url.getPath(), StandardCharsets.UTF_8);
     }
 
+    public static String getString(final URL url) {
+        return URLDecoder.decode(url.toString(), StandardCharsets.UTF_8);
+    }
+
     /**
      * Returns the URL to the parent directory of a File / Resource.
      * @param resourcePath The URL to analyze.
@@ -33,7 +37,7 @@ public final class UrlHelper {
      * @throws RuntimeException if the generated URL is not a valid URL.
      */
     public static URL getParentUrl(final URL resourcePath) throws ConfigurationParsingException {
-        String fileString = getPathString(resourcePath);
+        String fileString = getString(resourcePath);
         String parentString = fileString.substring(0, fileString.lastIndexOf("/"));
         try {
             return new URL(resourcePath.getProtocol(), resourcePath.getHost(), parentString);