Select One Choice attribute' LoV based on two bind variables, best practice

Question

Hello there,
I am in the process of learning the ADF 11g, I have following requirement,
A page must contain a list of school names which is needed to be fetched based on two parameters, the parameters are student information been inserted in the previous page.
I have defined a read only view "SchoolNamesViewRO", it's query depends on two bind variables :stdDegree and stdCateg.
added that RO View as a view accessor to the entity to which the name attribute belongs, and then add LoV for the name attribute using the ReadOnly view,
added the name attribute as Select One Choice to page2,
and now I need to pass the values of the bind variables of the ReadOnly view,
the information needed to be passed as the bind variables is inserted in the previous page, I could have the data as bindings attribute values in the page2 definition
I have implemented the next two appraoches but both resulted in an empty list :
* added ExecuteWithParams Action to the bindings of the page and then defined an Invoke Action (set refresh condition) in the executable s, set the default values of the parameters to be the attributes values' input value,
in the trace I code see that the binding fetches correct values as supposed , but the select list appears empty, does the this execution for the query considered to be connected to the list ?
* added a method to the ReadOnly view Imp java class to set the bind variables, then I define it as a MethodAction in the bindings , and then create an Invoke action for it , also the select is empty,
if the query been executed with the passed variables, then why the list is empty? is it reading data from another place than the page!
and what is the best practice to implement that requirement?
would the solution be : by setting the default value of the bind variables to be some kind of Expression!
please notice that query execution had the bound variables ( I see in the trace) are set to the correct values.
would you give some hints or redirect me to a useful link,
Thanks in advance
Regards,

Answer 1

please give me any example using backing bean .for example
<?xml version='1.0' encoding='UTF-8'?>
<jsp:root xmlns:jsp="http://java.sun.com/JSP/Page" version="2.1"
xmlns:f="http://java.sun.com/jsf/core"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:af="http://xmlns.oracle.com/adf/faces/rich">
<jsp:directive.page contentType="text/html;charset=UTF-8"/>
<f:view>
<af:document id="d1">
<af:form id="f1">
<af:selectOneChoice label="Label 1" id="soc1" binding="#{Af.l1}"
autoSubmit="true">
<af:selectItem label="A" value="1" id="si1"/>
<af:selectItem label="B" value="2" id="si2"/>
</af:selectOneChoice>
<af:selectOneChoice label="Label 2" id="soc2" disabled="#{Af.l1=='2'}"
partialTriggers="soc1">
<af:selectItem label="C" value="3" id="si3"/>
<af:selectItem label="D" value="4" id="si4"/>
</af:selectOneChoice>
</af:form>
</af:document>
</f:view>
</jsp:root>
package a;
import oracle.adf.view.rich.component.rich.input.RichSelectOneChoice;
public class A {
private RichSelectOneChoice l1;
public A() {
public void setL1(RichSelectOneChoice l1) {
this.l1 = l1;
public RichSelectOneChoice getL1() {
return l1;
is there any mistake