"Cannot serialize session attribute ..."

[Leffingwell, Jonathan R CTR FRCSE, JAX 7.2.2]

I am running a web app in IBM RAD 7 with a Tomcat 5.5.26 server, with
clustering (two Tomcat instances).  When shutting down the Tomcat server(s),
I get the following warning:

Mar 19, 2009 2:52:43 PM org.apache.catalina.session.StandardSession
writeObject
WARNING: Cannot serialize session attribute createXXXManager for session
8B1876E5C5C54B242E4256674843600B
java.io.NotSerializableException:
com.ibatis.dao.engine.impl.StandardDaoManager
        at
java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1081)
        at
java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1375)
        at
java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1347)
        at
java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1290)
        at
java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1079)
        at
java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:302)
        at
org.apache.catalina.session.StandardSession.writeObject(StandardSession.java
:1478)
        at
org.apache.catalina.session.StandardSession.writeObjectData(StandardSession.
java:948)
        at
org.apache.catalina.session.StandardManager.doUnload(StandardManager.java:51
7)
        at
org.apache.catalina.session.StandardManager.unload(StandardManager.java:463)
        at
org.apache.catalina.session.StandardManager.stop(StandardManager.java:667)
        at
org.apache.catalina.core.StandardContext.stop(StandardContext.java:4360)
        at
org.apache.catalina.core.ContainerBase.stop(ContainerBase.java:1067)
        at
org.apache.catalina.core.ContainerBase.stop(ContainerBase.java:1067)
        at
org.apache.catalina.core.StandardEngine.stop(StandardEngine.java:448)
        at
org.apache.catalina.core.StandardService.stop(StandardService.java:510)
        at
org.apache.catalina.core.StandardServer.stop(StandardServer.java:734)
        at org.apache.catalina.startup.Catalina.stop(Catalina.java:602)
        at org.apache.catalina.startup.Catalina.start(Catalina.java:577)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39
)
        at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl
.java:25)
        at java.lang.reflect.Method.invoke(Method.java:585)
        at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:295)
        at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:433)


All of my managers, including createXXXManager, inherit from a serializable
class BaseManager, but if I'm reading this correctly, it looks like the
iBatis class StandardDaoManager is not serializable.  I can't edit that
class, of course.

Here's what I want to know:

1.  If I put the following code in my context.xml file, will it prevent
clustering from working properly?

<Manager className="org.apache.catalina.session.PersistentManager"
saveOnRestart="false" />


2.  If the aforementioned context.xml snippet keeps clustering from working,
what options do I have to stop the warnings but keep clustering working
properly?


Thanks for any insight!

Jonathan

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