When trying to serialize user object we get following error on JBoss:

java.io.NotSerializableException: info.magnolia.cms.security.Realm$RealmImpl
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1156)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:326)
at java.util.LinkedList.writeObject(LinkedList.java:943)
at sun.reflect.GeneratedMethodAccessor476.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:945)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1461)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1392)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1150)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1509)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1474)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1392)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1150)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1509)
at java.io.ObjectOutputStream.defaultWriteObject(ObjectOutputStream.java:416)
at javax.security.auth.Subject.writeObject(Subject.java:963)
at sun.reflect.GeneratedMethodAccessor475.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:945)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1461)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1392)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1150)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:326)
at java.util.HashMap.writeObject(HashMap.java:1001)
at sun.reflect.GeneratedMethodAccessor470.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:945)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1461)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1392)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1150)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:326)
at org.jboss.ha.framework.server.SimpleCachableMarshalledValue.serialize(SimpleCachableMarshalledValue.java:271)
at org.jboss.ha.framework.server.SimpleCachableMarshalledValue.writeExternal(SimpleCachableMarshalledValue.java:252)
at java.io.ObjectOutputStream.writeExternalData(ObjectOutputStream.java:1421)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1390)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1150)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:326)
at org.jboss.cache.marshall.CacheMarshaller200.marshallObject(CacheMarshaller200.java:460)
at org.jboss.cache.marshall.CacheMarshaller300.marshallObject(CacheMarshaller300.java:47)
at org.jboss.cache.marshall.CacheMarshal