SimpleSelection doesn't work in Seam

[dxxvi]

I have 2 Seam components:

@Stateful
@Name("customerList")
public class CustomerListImpl implements CustomerList {
 @Logger
 protected Log log;

 @PersistenceContext(type= PersistenceContextType.EXTENDED)
 protected EntityManager entityManager;

 @DataModel("customers")
 protected List<Customer> customers;

 @In(value="customerComponents", required=false)
 protected CustomerComponents customerComponents;

 public void viewSelectedRows() {
 Iterator<Object> iterator = customerComponents.getSelection().getKeys();
 while (iterator.hasNext()) {
 Object key = iterator.next();
 customerComponents.getDataTable().setRowKey(key);
 Object customer = customerComponents.getDataTable().getRowData();
 customer = null;
 }
 }

 @SuppressWarnings("unchecked")
 public void findCustomers() {
 log.debug(null);
 customers = entityManager.createQuery("select c from Customer c").getResultList();
 }

 public void goToPanelBarItem() {
 log.debug(customerComponents.getPanelBar().getSelectedPanel());
 }

 @Destroy
 @Remove
 public void destroy() {
 }
}

@Local
public interface CustomerList {
 void viewSelectedRows();
 void findCustomers();
 void goToPanelBarItem();
 void destroy();
}

@Name("customerComponents")
@Scope(ScopeType.EVENT)
public class CustomerComponents {
 private HtmlScrollableDataTable dataTable;
 private SimpleSelection selection;
 private HtmlPanelBar panelBar;
 // ... getters & setters
}

My xhtml

<a4j:form>
 <rich:scrollableDataTable value="#{customers}" var="customer" width="70px" height="200px"
 binding="#{customerComponents.dataTable}"
 selection="#{customerComponents.selection}">
 <rich:column width="48px">
 <f:facet name="header">ID</f:facet>
 <h:outputText value="#{customer.id}" />
 </rich:column>
 </rich:scrollableDataTable>

 <a4j:commandLink value="View Selected Rows" action="#{customerList.viewSelectedRows}"
 reRender="selectedRowBox" />

 <rich:panelBar binding="#{customerComponents.panelBar}" width="500">
 <rich:panelBarItem name="barItem1" label="Leverage the whole set of JSF benefits ...">
 <a4j:support event="onenter" action="#{customerList.goToPanelBarItem}"/>
 Ajax4jsf is fully integrated ...
 </rich:panelBarItem>
 <rich:panelBarItem name="barItem2" label="Add AJAX capability...">
 <a4j:support event="onenter" action="#{customerList.goToPanelBarItem}"/>
 The framework is implemented ...
 </rich:panelBarItem>
 </rich:panelBar>
</a4j:form>
<h:panelGroup id="selectedRowBox"></h:panelGroup>

When I select some rows and click View Select Rows, the iterator is always empty.

When I enter a panel bar item, the goToPanelBarItem method prints the panel bar item name (that means the JSF component bindings work).

Does anybody know why the selection doesn't work?

Thank you.