General Rule on manipulating ViewObjects inside backing bean

Question

I've read in some articles and thread posts by that it is not advisable to manipulate ViewObjects inside a backin bean?
Are there any exceptions to this rule?
I have scenario where in my ViewObject is initially created and set to a MaxFetchSize(0) so that on the initial page load, I will just create a new blank row and BC4J will not query any data. However, there is also Search/Find buttons on the same page/viewobject that will query the database. So i will need to edit MaxFetchSize to a positive number so only then, data is queried from the DB. I put it in a backing bean method:
public String find() {
OperationBinding ob = (OperationBinding)bindings.get("Execute");
ViewObject vo = iteratorBinding.getViewObject();
vo.setMaxFetchSize(10);
ob.execute();
}So in effect, I manipulated the ViewObject inside the backing bean. Can this be considered an exception to the rule or best practice?
regards,
Anton

Answer 1

Anton,
you can call that method without writing a custom method in the VO. Just add an entry like this to your page def:
<methodAction IterBinding="SomeView1Iterator" id="setMaxFetchSize" MethodName="setMaxFetchSize"
                  RequiresUpdateModel="true" Action="999" IsViewObjectMethod="true" DataControl="AppModuleDataControl"
                  InstanceName="AppModuleDataControl.SomeView1">
      <NamedData NDName="val" NDValue="10" NDType="int"/>
    </methodAction>and in your backing bean:
    public String setMaxFetchSize_action() {
         FacesContext fc = FacesContext.getCurrentInstance();
         ValueBinding vb = fc.getApplication().createValueBinding("#{bindings}");
         DCBindingContainer dc = (DCBindingContainer) vb.getValue(fc);
         OperationBinding operationBinding = dc.getOperationBinding("setMaxFetchSize");
         operationBinding.execute();
         if (operationBinding.getErrors().isEmpty()){
             System.out.println("operation successful");
         else
             System.out.println("operation failed");
        return null;
    }no need to write and expose a VO client method.
Brenden