Newbie select struts

[pincopallo_it]

I have this lines in a jsp which use the struts select tag

<td>
<html:select name="SDatiForm" multiple="true" size="8"
property="listamisure" >
<htmlptions name="SDatiForm" property="listamisureid"
labelProperty="listamisure" />
</html:select>
</td>

I see my list but how can I tell struts that all the list Must be
selected when page opens ?

Thanks
Gianni