JSF: outputText doesn't not localize a Double-value

I want to localize the Double attribute value of the managed bean fooBean in Greek; i.e. number 12.3 should be 12,3 in greek locale (locale=el) and 12.3 in english locale (locale=en) Wrong code:

 <h:outputText value="#{fooBean.value}" />

Right code:

 <h:outputText value="#{fooBean.value">
    <f:convertNumber type="number" />
</h:outputText>