R12.1.3 OAF Controller Extension Can't seem to get value of DFF returned

I have a requirement to check the value of a DFF that is entered during requisition checkout.

I've extended CheckoutSummaryCO, and have this in my processFormRequest:

  public void processFormRequest(OAPageContext oapagecontext, OAWebBean oawebbean) {

       OAApplicationModule oaapplicationmodule = oapagecontext.getApplicationModule(oawebbean);

       String             s                  = oapagecontext.getParameter("event");

       if ("goto".equals(s) || "submit".equals(s) || "save".equals(s) || "editLines".equals(s)){

           String             current_user_id    = oapagecontext.getUserId()+"";

           OAApplicationModule appModule= oapagecontext.getApplicationModule(oawebbean);

           OADescriptiveFlexBean dff = (OADescriptiveFlexBean)oawebbean.findChildRecursive("ReqHeaderDFF");

           dff.processFlex(oapagecontext);

           OAWebBean dffBean=(OAWebBean)dff.findChildRecursive("ReqHeaderDFF4");

           OAMessageTextInputBean Stylebean = (OAMessageTextInputBean)dffBean;

           String first_approver = (String)Stylebean.getText(oapagecontext);

           OAException descMesg = new OAException("current user: "+current_user_id+" , first_approver: "+first_approver);