使用递归算法结合数据库解析成Java树形结构的代码解析

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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 }

总结

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