One common technique to implement generic deep clone is to take advantage of Java Serialization. The trick is simply to serialize/deserialize the object graph. However, this has the limitation that it only works for the portions of an object graph that implement Serializable.

To remove this constraint, we can apply similar technique with XStream, which doesn't require a class to implement Serializable for serializing deeply to/from XML. The deep clone would then work for all classes. (Note XStream does not serialize transient fields.)