code: public static String getJarManifestValue(Class clazz, String attrName) {
          URL url = getResource("/" + clazz.getName().replace('.', '/')
                  + ".class");
          if (url != null)
              try {
                  URLConnection uc = url.openConnection();
                  if (uc instanceof java.net.JarURLConnection) {
                      JarURLConnection juc = (JarURLConnection) uc;
                      Manifest m = juc.getManifest();
                      return m.getMainAttributes().getValue(attrName);
                  }
              } catch (IOException e) {
                  return null;
              }
          return null;
      }
docs: <p>getJarManifestValue.</p>
  
  @param clazz    a {@link java.lang.Class} object.
  @param attrName a {@link java.lang.String} object.
  @return a {@link java.lang.String} object.