docs: @Override
      public void onApplicationEvent(final ProfileSelectionEvent event) {
          final HttpSession session = event.getRequest().getSession(false);
  
          Assert.notNull(session, "Cannot store a profile selection into a null session.");
  
          session.setAttribute(this.attributeName, event.getRequestedProfileKey());
  
          logger.trace(
                  "Stored desired profile key [{}] into session (at attribute [{}]).",
                  event.getRequestedProfileKey(),
                  attributeName);
  
          final String fnameTheKeyMapsTo = this.mappings.get(event.getRequestedProfileKey());
  
          if (null == fnameTheKeyMapsTo) {
              logger.warn(
                      "The desired profile key {} has no mapping so will have no effect.",
                      event.getRequestedProfileKey());
          }
      }