hibernate生成tree

package yingjun.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 Tree {
	private int id;
	private String name;
	private Tree parent;
	private Set<Tree> children=new HashSet<Tree>();
	@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;
	}
	@ManyToOne
	@JoinColumn(name="parent_id")
	public Tree getParent() {
		return parent;
	}
	public void setParent(Tree parent) {
		this.parent = parent;
	}
	
	@OneToMany(mappedBy="parent",cascade=CascadeType.ALL,fetch=FetchType.EAGER)
	public Set<Tree> getChildren() {
		return children;
	}
	public void setChildren(Set<Tree> children) {
		this.children = children;
	}

	
}

 生成的建表语句：

 create table Tree (
        id integer not null auto_increment,
        name varchar(255),
        parent_id integer,
        primary key (id)
    )

    alter table Tree 
        add index FK27E7BE9FD80F87 (parent_id), 
        add constraint FK27E7BE9FD80F87 
        foreign key (parent_id) 
        references Tree (id)

 向树中插入数据：

@Test
	public void TestSaveTree(){
		
		Session session=HibernateUtil.getSessionFactory().getCurrentSession();
		session.beginTransaction();
		Tree tree1=new Tree();
		tree1.setName("图片");
		
		Tree tree2=new Tree();
		tree2.setName("照片");
		
		Tree tree3=new Tree();
		tree3.setName("海报");
		
		Tree tree4=new Tree();
		tree4.setName("我的照片1");
		
		Tree tree5=new Tree();
		tree5.setName("我的照片2");
		
		tree1.getChildren().add(tree2);
		tree1.getChildren().add(tree3);
		tree2.getChildren().add(tree4);
		tree2.getChildren().add(tree5);
		tree2.setParent(tree1);
		tree3.setParent(tree1);
		tree4.setParent(tree2);
		tree5.setParent(tree2);	
		
		session.save(tree1);
		session.getTransaction().commit();
	}

 结果：

 

 从树中取入数据代码：

@Test
	public void TestLoadTree(){
		Session session=HibernateUtil.getSessionFactory().getCurrentSession();
		session.beginTransaction();
		Tree t=(Tree)session.load(Tree.class, 1);
		print(t);
		session.getTransaction().commit();
		
		
	}

	private void print(Tree tree) {
		System.out.println(tree.getName());
		for(Tree child: tree.getChildren()){
			print(child);
		}

 取出结果：