code: private static String loadVersion(ClassLoader classLoader) throws IOException {
      try {
        Enumeration<URL> resources = classLoader.getResources("META-INF/MANIFEST.MF");
  
        while (resources.hasMoreElements()) {
          final URL url = resources.nextElement();
          final Manifest manifest = new Manifest(url.openStream());
          final Attributes mainAttributes = manifest.getMainAttributes();
          final String value = mainAttributes.getValue(IMPL_VERSION);
  
          if (value != null) {
            return value;
          }
        }
  
      } catch (IOException e) {
        LOG.error("Failed to read manifest", e);
        throw new IOException("Failed to find manifest", e);
      }
  
      return null;
    }
docs: Tries to load the first "Implementation-Version" manifest entry it can find in the given
  classloader.
  
  @param classLoader  The classloader to load manifests from
  @return a version string
  @throws IOException