使用递归算法结合数据库解析成Java树形结构的代码解析

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

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);

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}

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;}}

{  "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}