code: public void checkSkinName(final HttpServletRequest request) {
      String reqpar = request.getParameter(getSkinNameRequestName());
  
      if (reqpar != null) {
        if (reqpar.equals("!")) {
          // Go back to unsticky SkinName
          setSkinNameSticky(false);
        } else {
          setSkinName(reqpar);
          setSkinNameSticky(false);
        }
      }
  
      reqpar = request.getParameter(getSkinNameStickyRequestName());
      if (reqpar != null) {
        if (reqpar.equals("!")) {
          // Go back to unsticky SkinName
          setSkinNameSticky(false);
        } else {
          setSkinName(reqpar);
          setSkinNameSticky(true);
        }
      }
    }
docs: Allow user to explicitly set the skin name.
  
  @param request  Needed to locate session