public class ExternalizableDelegator
Delegates DataObject serialization while ensuring implementation independent
java.io.Serialization. An implementation of DataObject
returns an ExternalizableDelegator from its writeReplace() method.
The root DataObject is the object returned from do.getRootObject() where
do is the DataObject being serialized in a java.io.ObjectOutputStream.
When do.getContainer() == null then do is a root object.
The byte format for each DataObject in the stream is:
 [path] [root] // when do is not a root object
 [rootXML] // when do is a root object
 is the byte 0, serialized using writeByte(0).
 is the byte 1, serialized using writeByte(1).
[path] is an SDO path expression from the root DataObject to the serialized
DataObject such that root.getDataObject(path) == do.
Serialized using writeUTF(path).
[root] is the root object serialized using writeObject(root).
[rootXML] is the GZip of the XML serialization of the root DataObject.
The XML serialization is the same as
XMLHelper.INSTANCE.save(root, "commonj.sdo", "dataObject", stream);
where stream is a GZIPOutputStream, length is the number of bytes
in the stream, and bytes are the contents of the stream.
Serialized using writeInt(length), write(bytes).