<struts-config>
  ...
  <form-beans>
    ...
    <form-bean 
    	name="dispatchOptionForm"
        dynamic="true"
        type="org.apache.struts.action.DynaActionForm">
        <form-property name="option" type="java.lang.String"/>
    </form-bean>  
    ...
  </form-beans>
  ...
</struts-config>