code: @Override
      public String changeSessionId() {
          WebApp webapp = ((WebAppDispatcherContext) this._dispatchContext).getWebApp();
          
          HttpSession thisSession = ((SRTRequestContext31)_requestContext).generateNewId(webapp);
          
          return thisSession.getId();
      }
docs: /* (non-Javadoc)
  @see javax.servlet.http.HttpServletRequest#changeSessionId()