OK, Thanks for your explanation, i see clearer to use modeldriven or not. My problem is not about the populate the options of the checkboxlist but the exception rule you must select at least one.
In the XML file i have <field name=“personBean.levels”> <field-validator type=“fieldexpression> <param-name=“expression”>[!CDATA[#personBean.levels.length==0]]>></param> <message>You must select at least one option</message> </field-validator> </field> With that configuration i always obtain an error validation (showing the message in the checkboxñixt field) In Person class private String[] levels private String[] levelsAvalaible={“1ESO”, “2ESO”, 3ESO”, “4ESO” } with setters and getters In the register-input.jsp <form action=“register”> … <s:checkboxlist key=“personBean.levels” list=“levelsAvalaible”/> … </form> I can see the options of the checkboxlist, but even selecting one option and submit the form i get error validation. So i think It is a problem with the expression in the XML configuration. Un saludo, José A.