思路一：

1、准备表结构及对应的表数据
a、表结构：

create table TB_TREE(CID NUMBER not null,CNAME VARCHAR2(50),PID NUMBER //父节点)

b、表数据：

insert into tb_tree (CID, CNAME, PID) values (1, ‘中国‘, 0);insert into tb_tree (CID, CNAME, PID) values (2, ‘北京市‘, 1);insert into tb_tree (CID, CNAME, PID) values (3, ‘广东省‘, 1);insert into tb_tree (CID, CNAME, PID) values (4, ‘上海市‘, 1);insert into tb_tree (CID, CNAME, PID) values (5, ‘广州市‘, 3);insert into tb_tree (CID, CNAME, PID) values (6, ‘深圳市‘, 3);insert into tb_tree (CID, CNAME, PID) values (7, ‘海珠区‘, 5);insert into tb_tree (CID, CNAME, PID) values (8, ‘天河区‘, 5);insert into tb_tree (CID, CNAME, PID) values (9, ‘福田区‘, 6);insert into tb_tree (CID, CNAME, PID) values (10, ‘南山区‘, 6);insert into tb_tree (CID, CNAME, PID) values (11, ‘密云县‘, 2);insert into tb_tree (CID, CNAME, PID) values (12, ‘浦东‘, 4);

2、TreeNode对象，对应tb_tree

public class TreeNode implements Serializable {private Integer cid;private String cname;private Integer pid;private List nodes = new ArrayList(); public TreeNode() {} //getter、setter省略}

3、测试数据

public class TreeNodeTest {@Testpublic void loadTree() throws Exception{System.out.println(JsonUtils.javaToJson(recursiveTree(1)));} /*** 递归算法解析成树形结构** @param cid* @return* @author jiqinlin*/public TreeNode recursiveTree(int cid) {//根据cid获取节点对象(SELECT * FROM tb_tree t WHERE t.cid=?)TreeNode node = personService.getreeNode(cid);//查询cid下的所有子节点(SELECT * FROM tb_tree t WHERE t.pid=?)List childTreeNodes = personService.queryTreeNode(cid); //遍历子节点for(TreeNode child : childTreeNodes){TreeNode n = recursiveTree(child.getCid()); //递归node.getNodes().add(n);} return node;}}

输出的json格式如下：

{    "cid": 1,    "nodes": [        {            "cid": 2,            "nodes": [                {                    "cid": 11,                    "nodes": [                                             ],                    "cname": "密云县",                    "pid": 2                }            ],            "cname": "北京市",            "pid": 1        },        {            "cid": 3,            "nodes": [                {                    "cid": 5,                    "nodes": [                        {                            "cid": 7,                            "nodes": [                                                             ],                            "cname": "海珠区",                            "pid": 5                        },                        {                            "cid": 8,                            "nodes": [                                                             ],                            "cname": "天河区",                            "pid": 5                        }                    ],                    "cname": "广州市",                    "pid": 3                },                {                    "cid": 6,                    "nodes": [                        {                            "cid": 9,                            "nodes": [                                                             ],                            "cname": "福田区",                            "pid": 6                        },                        {                            "cid": 10,                            "nodes": [                                                             ],                            "cname": "南山区",                            "pid": 6                        }                    ],                    "cname": "深圳市",                    "pid": 3                }            ],            "cname": "广东省",            "pid": 1        },        {            "cid": 4,            "nodes": [                {                    "cid": 12,                    "nodes": [                                             ],                    "cname": "浦东",                    "pid": 4                }            ],            "cname": "上海市",            "pid": 1        }    ],    "cname": "中国",    "pid": 0}

**********************************************************************************************************************************************************

思路二：

数据库  id,name,parent_id

java对象：

private class TreeNode{    private String id;    private String name;    private String parentId;    private List<TreeNode> children;        // TODO getter/setter}

树构造代码如下：

        List<TreeNode> menuList = xxManager.findAllMenu();                List<TreeNode> nodeList = new ArrayList<TreeNode>();        for(TreeNode node1 : menuList){            boolean mark = false;            for(TreeNode node2 : menuList){                if(node1.getParentId()!=null && node1.getParentId().equals(node2.getId())){                    mark = true;                    if(node2.getChildren() == null)                        node2.setChildren(new ArrayList<TreeNode>());                    node2.getChildren().add(node1);                     break;                }            }            if(!mark){                nodeList.add(node1);             }        }        //转为json格式                String json = JSONArray.fromObject(nodeList).toString();        System.out.println("json:"+json);

原理如下图了：