code: @Override
      public String getSessionId() {
          return sessionSharedStorage.flatMap(storage -> storage.getSessionId()).orElseGet(() -> {
              if (isSuppressHttpSession()) { // needs to check because of or-created
                  String msg = "Not found the session ID of shared storage. (required if no http session)";
                  throw new IllegalStateException(msg);
              }
              return getSessionOrCreated().getId(); // normally here
          });
      }
docs: ================