15hibernate hibernate树状结构的设计（较重要）

@Entity
public class Org
{
	private int id;
	private String name;
	@OneToMany(cascade=CascadeType.All,mappedBy="parent")
	private Set<Org> children = new HashSet<Org>();
	@ManyToOne
	@JoinColumn(name="parent_id")
	private Org parent;
}

public void testSave(){
	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 o11 = new Org();
	o11.setName("分公司1下部门1");
	Org o12 = new Org();
	o12.setName("分公司1下部门2");

	o.getChildren().add(o1);
	o.getChildren().add(o2);
	o1.getChildren().add(o11);
	o1.getChildren().add(o12);
	o11.setParent(o1);
	o12.setParent(o1);
	o1.setParent(o);
	o2.setParent(o);

	Session session = sessionFactory.openSession();
	session.beginTransaction();
	session.save(o);
	session.getTransaction().commit();
	session.close();
}

public void testLoad(){
	testSave();

	Session session = sessionFactory.openSession();
	session.beginTransaction();

	Org o = (Org)session.load(Org.class,1);
	print(o,0);
	session.getTransaction().commit();
	session.close();
}

public void print(Org o,int level){//树状结构的递归
	String preStr = "";
	for(int i=0;i<level;i++){
		preStr += "----";
	}
	System.out.println(o.getName());
	for(Org child : o.getChildren()){
		print(child,level);//level展现树状结构，缩进
	}
}//如果树很大，就不要用eager，这时采用ajax比较好