hibernate 自生双向一对多 多对一管理 （树）

<span style="font-size: large;">package com.javacrazyer.test;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import javax.persistence.Version;

/**
 * 产品类别
 *
 */
@Entity
@Table(name="category")
public class Category implements Serializable{
	private static final long serialVersionUID = -3942148673242309324L;
	@Id
	@GeneratedValue
	private Integer id;
	@Version
	private Integer version;
	private String name;
	private String description;
	private String path;  //分类路径

	//Category 自身双向多对一
	@ManyToOne(cascade={CascadeType.MERGE,CascadeType.PERSIST})
	private Category parent;

	//Category 自身双向一对多
	@OneToMany(mappedBy="parent",fetch=FetchType.EAGER,cascade=CascadeType.ALL)
	@JoinColumn(name="parent_id")
	private List<Category> child = new ArrayList<Category>();

	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getDescription() {
		return description;
	}
	public void setDescription(String description) {
		this.description = description;
	}
	public Category getParent() {
		return parent;
	}
	public void setParent(Category parent) {
		this.parent = parent;
	}
	public List<Category> getChild() {
		return child;
	}
	public void setChild(List<Category> child) {
		this.child = child;
	}
	public Integer getVersion() {
		return version;
	}

	@SuppressWarnings("unused")
	private void setVersion(Integer version) {
		this.version = version;
	}
	public String getPath() {
		return path;
	}
	public void setPath(String path) {
		this.path = path;
	}
}</span>