a problem about Axis in a tomcat5 cluster

[moch]

Hi all........
 
I am using axis in a tomcat5 cluster: Apache2.0.48 + 
jakarta-tomcat-connectors-jk2.0.2-win32-apache2.0.43.
 
load balance run successfully, but Session replication has an error.
 
>From tomcat's document, any attribute value that you store in the session has to 
>implement the java.io.Serializable Interface.
But from axis1.1's document, "Session" scope will create a new object for each 
session-enabled client who accesses your service. 
 
while I try to call an session-oriented services, it throw an exception:
java.lang.IllegalArgumentException: Value for attribute CountTest is not serial
izable.
 
It seems that tomcat5 try to put instance of CountTest into Session. yet after 
WSDL2Java, CountTest is an Interface extend java.rmi.Remote. 
 
How can I make session replication of axis in a tomcat cluster?
 
thanks.
 
the origin class is :
 
public class CountTest{
    private int total;
    public void(String input){
        .........
    }
}