感谢有奉献精神的人
转自：/question/129154_235324
构造treelist的过程可以使用递归查询获取，表结构如下
create table TB_TREE
(
id NUMBER not null,
name VARCHAR2(50),
parentId NUMBER //父节点
)
Postgre Sql：
select 语句如下，oracle可以用 start with connect by prior实现类似功能
WITH RECURSIVE r AS (
SELECT
a.id, a.parentid, a.name
FROM TB_TREE a WHERE id= 976
union ALL
SELECT
b.id, b.parentid, b.name
FROM TB_TREE b, r WHERE b.parentid = r.id
)
select
id, parentid, name
from r
import java.util.ArrayList; import java.util.List; public class Tree { private int id;private String name;private int parentId;private List childrens; public Tree(int id,String name,int parentId){this.id = id;this.name = name;this.parentId = parentId; }public int getId() {return id; } public void setId(int id) {this.id = id; } public String getName() {return name; } public void setName(String name) {this.name = name; } public int getParentId() {return parentId; } public void setParentId(int parentId) {this.parentId = parentId; } public List getChildrens() {return childrens; } public void setChildrens(List childrens) {this.childrens = childrens; } @Override public String toString() {return "Tree [id=" + id + ", name=" + name + ", parentId=" + parentId + ", childrens=" + childrens + "]"; } public static void main(String[] args) {Tree tree1 = new Tree(1, "顶层节点1", 0);Tree tree2 = new Tree(2, "顶层节点2", 0);Tree tree3 = new Tree(3, "顶层节点3", 0);Tree tree4 = new Tree(4, "二级节点4", 1);Tree tree5 = new Tree(5, "二级节点5", 2);Tree tree6 = new Tree(6, "二级节点6", 3);Tree tree7 = new Tree(7, "三级节点7", 4);Tree tree8 = new Tree(8, "三级节点8", 4);Tree tree9 = new Tree(9, "三级节点9", 5);List trees = new ArrayList();trees.add(tree9);trees.add(tree8);trees.add(tree7);trees.add(tree6);trees.add(tree5);trees.add(tree4);trees.add(tree3);trees.add(tree2);trees.add(tree1);List rootTrees = new ArrayList();for (Tree tree : trees) { if(tree.getParentId() == 0){ rootTrees.add(tree); } for (Tree t : trees) { if(t.getParentId() == tree.getId()){ if(tree.getChildrens() == null){ List myChildrens = new ArrayList(); myChildrens.add(t); tree.setChildrens(myChildrens); }else{ tree.getChildrens().add(t); } } }}for (Tree tree : rootTrees) { System.out.println(tree.toString());} } }
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