spring - Serializable error Spring+Weblogic Cluster

Question

I have an application with Weblogic 11g in cluster, Spring 3 and JSF Mojarra. There are: JavaBean (Serializable), ManagedBeans (Serializable for view/session), Service, DAO.

I got the error:

**All session objects should be serializable to replicate. 
Check the objects in your  session. Failed to replicate non-serializable object. 
java.rmi.MarshalException: failed to marshal update(Lweblogic.cluster.replication.ROID;ILjava.io.Serializable;Ljava.lang.Object;); nested exception is:
    java.io.NotSerializableException: com.emp.service.impl.DemandaServiceImpl$$EnhancerByCGLIB$$4fae7872

Is it necessary to become serializable Service layer ? I do not want to put in session and replicate it.

Spring is running with:

<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

Every Spring Bean in my applicationContext.xml automatically will be in HttpServletRequest, ServletContext or HttpSession?

If Yes, what is the solution to avoid Service layer serialization ?