The Struts-config.xml is as follows:

<form-bean dynamic="true" name="FormCircuitos" type="org.apache.struts.action.DynaActionForm" >
     <form-property name="Clase" type="java.lang.String" />
   .
   .
   .
</form-bean>

and the catalina.out I get this error.

WARN No puedo serializar atributo de sesi?n FormCircuitos para sesi?n 772D050829571AEA6C6E7135C8BE60DA

 
And the question is how the serialization DynaActionForm.????????

Thanks.