EDIT

import javax.xml.bind.annotation.XmlAccessType;

import javax.xml.bind.annotation.XmlAccessorType;

import javax.xml.bind.annotation.XmlElement;

import javax.xml.bind.annotation.XmlRootElement;

import javax.xml.bind.annotation.XmlType;

import org.apache.log4j.Logger;

	//private Set<FeatureNode> nodes = new HashSet<FeatureNode>();

	@XmlElement(name = "Root")

	@OneToOne(fetch = FetchType.LAZY)

	@Cascade({CascadeType.SAVE_UPDATE, CascadeType.MERGE})

	private FeatureNode root;