question: @ Override public void writeExternal ( ObjectOutput out ) throws IOException { String tid = getThreadMapping ( ) ; out . writeObject ( tid ) ; out . writeObject ( this . userTransactionServerLookupName ) ; out . writeObject ( this . initialContextFactory ) ; out . writeObject ( this . providerUrl ) ; out . writeInt ( this . timeout ) ; }
target:  Needed to ship instances across the network among clients.