使用遞歸算法結合數據庫解析成java樹形結構

一、準備表結構及對應的表數據
a、表結構：

create table TB_TREE
(
CID NUMBER not null,
CNAME VARCHAR2(50),
PID NUMBER //父節點
)

b、表數據：

insert into tb_tree (CID, CNAME, PID) values (1, '中國', 0);
insert into tb_tree (CID, CNAME, PID) values (2, '北京市', 1);
insert into tb_tree (CID, CNAME, PID) values (3, '廣東省', 1);
insert into tb_tree (CID, CNAME, PID) values (4, '上海市', 1);
insert into tb_tree (CID, CNAME, PID) values (5, '廣州市', 3);
insert into tb_tree (CID, CNAME, PID) values (6, '深圳市', 3);
insert into tb_tree (CID, CNAME, PID) values (7, '海珠區', 5);
insert into tb_tree (CID, CNAME, PID) values (8, '天河區', 5);
insert into tb_tree (CID, CNAME, PID) values (9, '福田區', 6);
insert into tb_tree (CID, CNAME, PID) values (10, '南山區', 6);
insert into tb_tree (CID, CNAME, PID) values (11, '密雲縣', 2);
insert into tb_tree (CID, CNAME, PID) values (12, '浦東', 4);

二、TreeNode對象，對應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
}

三、測試數據

public class TreeNodeTest {
@Test
public void loadTree() throws Exception{
System.out.println(JsonUtils.javaToJson(recursiveTree(1)));
}
 
/**
* 遞歸算法解析成樹形結構
*
* @param cid
* @return
* @author jiqinlin
*/
public TreeNode recursiveTree(int cid) {
//根據cid獲取節點對象(SELECT * FROM tb_tree t WHERE t.cid=?)
TreeNode node = personService.getreeNode(cid);
//查詢cid下的全部子節點(SELECT * FROM tb_tree t WHERE t.pid=?)
List childTreeNodes = personService.queryTreeNode(cid); 
//遍歷子節點
for(TreeNode child : childTreeNodes){
TreeNode n = recursiveTree(child.getCid()); //遞歸
node.getNodes().add(n);
}
 
return node;
}
}

輸出的json格式以下：

{
    "cid": 1,
    "nodes": [
        {
            "cid": 2,
            "nodes": [
                {
                    "cid": 11,
                    "nodes": [
                         
                    ],
                    "cname": "密雲縣",
                    "pid": 2
                }
            ],
            "cname": "北京市",
            "pid": 1
        },
        {
            "cid": 3,
            "nodes": [
                {
                    "cid": 5,
                    "nodes": [
                        {
                            "cid": 7,
                            "nodes": [
                                 
                            ],
                            "cname": "海珠區",
                            "pid": 5
                        },
                        {
                            "cid": 8,
                            "nodes": [
                                 
                            ],
                            "cname": "天河區",
                            "pid": 5
                        }
                    ],
                    "cname": "廣州市",
                    "pid": 3
                },
                {
                    "cid": 6,
                    "nodes": [
                        {
                            "cid": 9,
                            "nodes": [
                                 
                            ],
                            "cname": "福田區",
                            "pid": 6
                        },
                        {
                            "cid": 10,
                            "nodes": [
                                 
                            ],
                            "cname": "南山區",
                            "pid": 6
                        }
                    ],
                    "cname": "深圳市",
                    "pid": 3
                }
            ],
            "cname": "廣東省",
            "pid": 1
        },
        {
            "cid": 4,
            "nodes": [
                {
                    "cid": 12,
                    "nodes": [
                         
                    ],
                    "cname": "浦東",
                    "pid": 4
                }
            ],
            "cname": "上海市",
            "pid": 1
        }
    ],
    "cname": "中國",
    "pid": 0
}