http://forum.zkoss.org/question/80007/listbox-selecteditems-and-hibernate-collection-types-dont-play-together/

the root cause is, FormELResolver doesn't return a appropriate Type when EL parser try to set a value to a form.
basically, I think FormELResolver should always return null type because it is just a middle container, it doesn't need to care the type for coerceTo of parser