hibernate树

package com.test.model;

import java.util.HashSet;
import java.util.Set;

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;

@Entity
public class Org {
    private int id;
    private String name;
    private Set<Org> children = new HashSet<Org>();
    private Org parent;
    
    @Id
    @GeneratedValue
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    
    @OneToMany(mappedBy="parent", cascade=CascadeType.ALL, fetch=FetchType.EAGER)
    public Set<Org> getChildren() {
        return children;
    }
    public void setChildren(Set<Org> children) {
        this.children = children;
    }
    
    @ManyToOne
    @JoinColumn(name="parent_Id")
    public Org getParent() {
        return parent;
    }
    public void setParent(Org parent) {
        this.parent = parent;
    }
}

package com.test.test;

import org.hibernate.classic.Session;

import com.test.Util.HibernateUtil;
import com.test.model.Org;

public class StudentManager {
    public static void main(String[] args) {
        new StudentManager().testSave();
    }
    
    public void testSave() {
        Session session = HibernateUtil.getSessionFactory().getCurrentSession();
        session.beginTransaction();
        
        Org o = new Org();
        o.setName("总公司");
        
        Org o1 = new Org();
        o1.setName("分公司1");
        
        Org o2 = new Org();
        o2.setName("分公司2");
        
        Org o21 = new Org();
        o21.setName("分公司2_1");
        
        Org o22 = new Org();
        o22.setName("分公司2_2");
        
        o.getChildren().add(o1);
        o.getChildren().add(o2);
        
        o1.setParent(o);
        
        o2.setParent(o);
        o2.getChildren().add(o21);
        o2.getChildren().add(o22);
        
        o21.setParent(o2);
        o22.setParent(o2);
        
        session.save(o);
        testLoad();
        session.getTransaction().commit();
    }
    
    public void testLoad() {
        Session session = HibernateUtil.getSessionFactory().getCurrentSession();
        session.beginTransaction();
        Org org = (Org)session.load(Org.class, 1);
        print(org, 0);
        
    }

    private void print(Org org, int level) {
        String str = "----";
        for(int i=0; i<level; i++) {
            System.out.print(str);
        }
        
        System.out.println(org.getName());
        level++;
        for(Org o:org.getChildren()) {
            print(o, level);
        }
    }
}