for (final WebResource possibleJar : possibleJars) {
            if (possibleJar.isFile() && possibleJar.getName().endsWith(".jar")) {
                try (final JarFile jarFile = new JarFile(possibleJar.getCanonicalPath())) {
                    final Manifest manifest = jarFile.getManifest();
                    if (manifest != null && manifest.getEntries() != null) {
                        final Attributes attributes = manifest.getMainAttributes();

        if (jarFiles == null) {
            return nameSet.stream().sorted().collect(Collectors.toList());
        }
        for (final File jarFile : jarFiles) {
            try (FileSystem fs = FileSystems.newFileSystem(jarFile.toPath(), ClassLoader.getSystemClassLoader())) {
                final Path xmlPath = fs.getPath("fess_ds++.xml");
                if (!Files.exists(xmlPath)) {

                    final JarURLConnection jarURLConnection = (JarURLConnection) resource.openConnection();
                    try (JarFile jarFile = jarURLConnection.getJarFile()) {
                        final Enumeration<JarEntry> entries = jarFile.entries();
                        while (entries.hasMoreElements()) {
                            final JarEntry entry = entries.nextElement();