why java.io.NotSerializableException: org.apache.catalina.se

[javang]

Hi,all
I deploy my app in jboss4.2.2 or 5.0.4 cluster Environment ,at Servlet layer implements java.io.Serializable interface,but when i access my app,why trace down error message:
<log4j:event logger="org.jboss.web.tomcat.service.session.JBossCacheService" timestamp="1205303327632" level="ERROR" thread="http-127.0.0.1-8080-1">
<log4j:message><![CDATA[externalizeSession(): exception occurred externalizing session SessionBasedClusteredSession[id: HLROTf85JnuT1+TwHyPEYA__.sa lastAccessedTime: 1205303321784 version: 1 lastOutdated: 0]]]></log4j:message>
<log4j:throwable><![CDATA[java.io.NotSerializableException: org.apache.catalina.session.StandardSessionFacade
at java.io.ObjectOutputStream.writeObject0(Unknown Source)
at java.io.ObjectOutputStream.defaultWriteFields(Unknown Source)
at java.io.ObjectOutputStream.writeSerialData(Unknown Source)
at java.io.ObjectOutputStream.writeOrdinaryObject(Unknown Source)
at java.io.ObjectOutputStream.writeObject0(Unknown Source)
at java.io.ObjectOutputStream.writeObject(Unknown Source)
at java.util.concurrent.ConcurrentHashMap.writeObject(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at java.io.ObjectStreamClass.invokeWriteObject(Unknown Source)
at java.io.ObjectOutputStream.writeSerialData(Unknown Source)
at java.io.ObjectOutputStream.writeOrdinaryObject(Unknown Source)
at java.io.ObjectOutputStream.writeObject0(Unknown Source)
at java.io.ObjectOutputStream.writeObject(Unknown Source)
at org.jboss.web.tomcat.service.session.SessionBasedClusteredSession.writeExternal(SessionBasedClusteredSession.java:176)
at org.jboss.web.tomcat.service.session.JBossCacheService.externalizeSession(JBossCacheService.java:1220)
at org.jboss.web.tomcat.service.session.JBossCacheService.putSession(JBossCacheService.java:378)
at org.jboss.web.tomcat.service.session.JBossCacheClusteredSession.processSessionRepl(JBossCacheClusteredSession.java:122)
at org.jboss.web.tomcat.service.session.JBossCacheManager.processSessionRepl(JBossCacheManager.java:1275)
at org.jboss.web.tomcat.service.session.JBossCacheManager.storeSession(JBossCacheManager.java:800)
at org.jboss.web.tomcat.service.session.InstantSnapshotManager.snapshot(InstantSnapshotManager.java:49)
at org.jboss.web.tomcat.service.session.ClusteredSessionValve.invoke(ClusteredSessionValve.java:100)
at org.jboss.web.tomcat.service.session.JvmRouteValve.invoke(JvmRouteValve.java:87)
at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:90)
at org.jboss.web.tomcat.security.SecurityContextEstablishmentValve.invoke(SecurityContextEstablishmentValve.java:96)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:157)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:309)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:601)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Unknown Source)
]]></log4j:throwable>
</log4j:event>

[brian.stansberry]

You are placing the session itself (or some object with a reference to the session) as an attribute in the session. You cannot do this as the session is not serializable.