Programmatically changing validation property in view criteria

In many cases we need to conditionally change the validation property of view criteria  ( we can change required / Selectively Required / Optional property in Query panel ).There is a method called setRequiredString(String) in ViewCriteriaItem object for achieving this requirement. Argument of this method is “Optional ” or “Required” or “SelectivelyRequired”. I am calling changeValidation() from queryOperationListener of af:Query component.In UI you can refresh your query component by self reference of partial trigger. Below code is self explanatory .    

<af:query id="qryId1" headerText="Search" disclosed="true"
                    value="#{bindings.Search_region_Name.queryDescriptor}"
                    model="#{bindings.Search_region_Name.queryModel}"
                    queryListener="#{backingBeanScope.BeanName.processQuery}"
                    queryOperationListener="#{backingBeanScope.BeanName.queryOperationListener}"
                    partialTriggers="::qryId1"/>

Managed Bean Code
    public void queryOperationListener(QueryOperationEvent queryOperationEvent)

    {
        JSFUtils.resloveMethodExpression("#{bindings.Employees1.collectionModel.makeCurrent}",
                                         Object.class,
                                         new Class[] { QueryOperationEvent.class },
                                         new Object[] { queryOperationEvent });

        if (queryOperationEvent.getOperation().equals(QueryOperationEvent.Operation.CRITERION_UPDATE)) {
            changeValidation();
        }
    }

    private void changeValidation() {


        DCDataControl dataControl =
            BindingContext.getCurrent().findDataControl("xxxAppModuleDataControl");
        ApplicationModule am =
            (ApplicationModule)dataControl.getDataProvider();


        ViewObject vo = am.findViewObject("VO_Instance_Name");
        ViewCriteria viewCriteria =
            vo.getViewCriteriaManager().getViewCriteria("View_Criteria_Name");
        ArrayList criteriaItems =
            (ArrayList)((ViewCriteriaRow)viewCriteria.getRows().get(0)).getCriteriaItems();
        Iterator iterator = criteriaItems.iterator();


        while (iterator.hasNext()) {
            ViewCriteriaItem item = (ViewCriteriaItem)iterator.next();
            if (item.getName().equalsIgnoreCase("View_Attribute_Name")) {
                ((ViewCriteriaItem)criteriaItems.get(2)).setRequiredString("SELECTIVELY_REQUIRED");


                if ((null != item.getValue())) {


                    ((ViewCriteriaItem)criteriaItems.get(0)).setRequiredString("Optional");
                    ((ViewCriteriaItem)criteriaItems.get(1)).setRequiredString("Optional");
                } else {
                    ((ViewCriteriaItem)criteriaItems.get(0)).setRequiredString("SelectivelyRequired");
                    ((ViewCriteriaItem)criteriaItems.get(1)).setRequiredString("Required");
                }
            }
        }
    }