使用递归算法结合数据库解析成java树形结构

使用递归算法结合数据库解析成java树形结构

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 {
@Test
public 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
}