code: static void setPreventCache( ServletRequest request ) {
          assert request != null;
          request.setAttribute(PREVENT_CACHE_ATTR, Boolean.TRUE);
      }
docs: Make sure that when this page is rendered, it will set headers in the response to prevent caching.
  Because these headers are lost on server forwards, we set a request attribute to cause the headers
  to be set right before the page is rendered.  This attribute can be read via
  {@link #isPreventCache(javax.servlet.ServletRequest)}.
  
  @param request the servlet request