private static String getLibraryJarfiles(String dir) {
        try {

            String ret = "";
            for (File item : new File(dir).listFiles()) {
                if (item.isDirectory()) {
                    ret += getLibraryJarfiles(item.getCanonicalPath());
                } else {
                    if (item.getName().endsWith(".jar")) {
                        ret += item.getCanonicalPath() + ";";
                    }
                }
            }
            return ret;

        } catch (Exception ex) {
            Logger.error("PackBuilder.getLibraryJarfiles", ex.getMessage(), false, ex);
            return null;
        }
    }