Rapidly clicking on a button causes exceptions to be thrown

 13:33:50,218 ERROR [D2DFaceletViewHandler] Problem in renderResponse:
      /pricing/viewAdjustPremium.jspx @39,80 itemValue="${layer.value}":
      /pricing/viewAdjustPremium.jspx @38,110 items="#{ctrl.pricingConversation.x}":
      Exception getting value of property pricingConversation of base of type :
      com.agcs.pricing.web.controller.ViewAdjustPremiumController_$$_javassist_39
 javax.faces.el.EvaluationException: /pricing/viewAdjustPremium.jspx @39,80 itemValue="${x.value}":
      /pricing/viewAdjustPremium.jspx @38,110 items="#{viewadjustpremiumcontroller.pricingConversation.x}":
      Exception getting value of property pricingConversation of base of type :
      com.agcs.pricing.web.controller.ViewAdjustPremiumController_$$_javassist_39
      at com.sun.facelets.el.LegacyValueBinding.getValue(LegacyValueBinding.java:60)
      ....

The following change has been suggested, however, synchronization must be considered carefully as it can lead to deadlock or performance problems:

 public class ViewBoundAdaptingServlet extends BasicAdaptingServlet {
 
     synchronized public void service(HttpServletRequest request, HttpServletResponse response) throws Exception {
        ...
     }
 }