question: @ Override public void toData ( DataOutput out ) throws IOException { out . writeInt ( maxInactiveInterval ) ; out . writeLong ( lastAccessedTime ) ; synchronized ( attributes ) { out . writeInt ( attributes . size ( ) ) ; for ( Map . Entry < String , Object > entry : attributes . entrySet ( ) ) { DeltaEvent delta = new DeltaEvent ( true , entry . getKey ( ) , entry . getValue ( ) ) ; DataSerializer . writeObject ( delta , out ) ; } } out . writeUTF ( jvmOwnerId ) ; }
target:  Use DeltaEvents to propagate the actual attribute data - DeltaEvents turn the values into byte arrays which means that the actual domain classes are not required on the server.