It would be nice if we could have mappings that are more resistant to changes in the target object. There's no way to flat-out exclude source properties from mapping, the closest approximation would be unmappedSourcePolicy = WARN in combination with ignoreUnmappedSourceProperties. However, it's not robust, as you won't get notified if a property in ignoreUnmappedSourceProperties suddenly starts getting mapped, because a matching field was added in the target object. It would make sense if there was a warning or error, possibly depending on unmappedSourcePolicy.