docs: public void invalidate ()
    {
      if (m_bInvalidated)
        throw new IllegalArgumentException ("Servlet pool already invalidated!");
      m_bInvalidated = true;
  
      // Destroy all servlets
      for (final ServletItem aServletItem : m_aServlets)
        try
        {
          aServletItem.getServlet ().destroy ();
        }
        catch (final Exception ex)
        {
          if (LOGGER.isErrorEnabled ())
            LOGGER.error ("Failed to destroy servlet " + aServletItem, ex);
        }
  
      m_aServlets.clear ();
    }