code: protected String getManifestAttributeValue(Attributes.Name attributeName) {
          try {
              String value = attributes.getValue(attributeName);
              return value != null ? value : "undefined";
          } catch (NullPointerException e) {
              return "undefined";
          } catch (IllegalArgumentException e) {
              logger.error("Invalid attribute name when reading jar manifest for reading version information: " + e.getMessage());
              return "undefined";
          }
      }
docs: Gets the value of an attribute of the manifest.
  
  @param attributeName the name of the attribute
  @return the value of the attribute, or "undefined" if the attribute couldn't be read