code: private HttpSession2 buildSession(boolean create) {
          if (create) {
              session = buildSession(sessionManager.getSessionIdGenerator().generate(request), true);
              log.debug("Build new session[{}].", session.getId());
              return session;
          } else {
              return null;
          }
      }
docs: build a new session
  @param create create session or not
  @return session