实现树结构

package com.lzj.www.model;

import java.util.ArrayList;
import java.util.List;

public class Node {

	private Integer cid;
	private String name;
	private Integer pid;
	//用于存放它的子节点
	private List<Node> node = new ArrayList<>();
	
	
	//getter、setter方法
}

private Node getTree(Integer cid){
         //dao:  sql="select * from tree where cid = ?"  :找到cid的对应节点　　　　　　
	Node node = daoTest.getOwn(cid);
         //dao:  sql="select * from tree where pid = ?"   :找到cid对应节点的子节点
　　      //这里要防止空指针异常，因此在dao层创建一个List<Node>的时候就该指定地址
	List<Node> cList = daoTest.getChild(cid);
	for(Node n : cList){
                  //用递归实现树 
		Node cNode = getTree(n.getCid());
		node.getNode().add(cNode);
	}
	return node;
}
	
@Test
public void testTree(){
	JSONObject object = JSONObject.fromObject(getTree(1));
	System.out.println(object.toString());
}