groupBy="true" not working

I have been struggling with groupBy="true". The Group by column as shown in http://www.irian.at/myfaces/simpleGroupBy.jsf does not work in my code:

<h:dataTable value="#{test.items}" var="item">

<t:column groupBy="true">

<f:facet name="header">

<t:outputText style="font-weight: bold;" value="Col1" />

</f:facet>

<t:outputText value="#{item.colItem1}" />

</t:column>

<t:column>

<f:facet name="header">

<t:outputText style="font-weight: bold;" value="Vendor"/>

</f:facet>

<t:outputText value="#{item.colItem2}" />

</t:column>

</t:dataTable>

What am I missing?

Thanks!

[753 byte] By [javaBuffa] at [2007-11-26 17:39:00]