Java实现树状结构解析

数据库信息

 代码实现

实体类
public class ChainTree implements Serializable {
    private static final long serialVersionUID = 1L;

    private Integer id;
    private Integer province;
    private String city;
    private String name;
    private List children;
//省略get set方法

package com.ruoyi.zhihui.controller;

import com.ruoyi.common.core.controller.BaseController;
import com.ruoyi.common.core.domain.AjaxResult;
import com.ruoyi.system.domain.ChainTree;
import com.ruoyi.system.mapper.SysDeptMapper;
import com.ruoyi.zhihui.mapper.OtherMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

@RestController
@RequestMapping("/test")
public class DeptController extends BaseController {

    @Autowired
    private OtherMapper otherMapper;

    @GetMapping("/tree")
    public AjaxResult getTree() {
        //查询表所有信息
        List trees = otherMapper.getTree();
        //创建空集合信息存放id
        List integers = new ArrayList<>();
        //创建空的数据集合
        List treeList = new ArrayList<>();
        //循环数据库查出来的数据
        for (ChainTree tree : trees) {
            //Integer集合存放 数据id信息
            integers.add(tree.getId());
        }
        //循环数据库查出来的数据
        for (ChainTree chainTree : trees) {
            //如果是顶级节点
            if (!integers.contains(chainTree.getProvince())) {
                //那么添加子节点
                addChildren(trees, chainTree);
                //将数据添加到刚才创建的空数据集合
                treeList.add(chainTree);
            }
        }
        //返回结果信息
        return AjaxResult.success(treeList);
    }

    
    private void addChildren(List trees, ChainTree chainTree) {
        //子节点集合信息
        List treeList = selectChildren(trees, chainTree);
        //设置子节点
        chainTree.setChildren(treeList);
        //查看子节点下面是否还有子节点数据
        for (ChainTree tree : treeList) {
            //如果子节点下面还有数据
            if (selectChildren(trees, tree).size() > 0) {
                //递归算法运行循环本身
                addChildren(trees, tree);
            }
        }
    }

    
    private List selectChildren(List trees, ChainTree chainTree) {
        //创建空的子节点集合
        List treeList = new ArrayList<>();
        //使用迭代器 循环数据
        Iterator chainTreeIterator = trees.iterator();
        //如果集合有数据
        while (chainTreeIterator.hasNext()) {
            //将数据赋值给对象
            ChainTree tree = chainTreeIterator.next();
            //如果节点相等
            if (tree.getProvince() == chainTree.getId()) {
                //添加进子节点
                treeList.add(tree);
            }
        }
        //返回子节点数据
        return treeList;
    }
}

结果展示

{
    "msg": "操作成功",
    "code": 200,
    "data": [
        {
            "id": 1,
            "province": 0,
            "city": "0",
            "name": "中国",
            "children": [
                {
                    "id": 2,
                    "province": 1,
                    "city": "0.1",
                    "name": "河北省",
                    "children": [
                        {
                            "id": 5,
                            "province": 2,
                            "city": "0.1.2",
                            "name": "石家庄市",
                            "children": null
                        },
                        {
                            "id": 6,
                            "province": 2,
                            "city": "0.1.2",
                            "name": "唐山市",
                            "children": null
                        },
                        {
                            "id": 7,
                            "province": 2,
                            "city": "0.1.2",
                            "name": "秦皇岛市",
                            "children": null
                        },
                        {
                            "id": 8,
                            "province": 2,
                            "city": "0.1.2",
                            "name": "邯郸市",
                            "children": null
                        }
                    ]
                },
                {
                    "id": 3,
                    "province": 1,
                    "city": "0.1",
                    "name": "山西省",
                    "children": [
                        {
                            "id": 9,
                            "province": 3,
                            "city": "0.1.3",
                            "name": "大同市",
                            "children": null
                        },
                        {
                            "id": 10,
                            "province": 3,
                            "city": "0.1.3",
                            "name": "朔州市",
                            "children": null
                        },
                        {
                            "id": 11,
                            "province": 3,
                            "city": "0.1.3",
                            "name": "忻州市",
                            "children": null
                        },
                        {
                            "id": 12,
                            "province": 3,
                            "city": "0.1.3",
                            "name": "吕梁市",
                            "children": null
                        }
                    ]
                },
                {
                    "id": 4,
                    "province": 1,
                    "city": "0.1",
                    "name": "辽宁省",
                    "children": [
                        {
                            "id": 13,
                            "province": 4,
                            "city": "0.1.4",
                            "name": "沈阳市",
                            "children": null
                        },
                        {
                            "id": 14,
                            "province": 4,
                            "city": "0.1.4",
                            "name": "大连市",
                            "children": null
                        },
                        {
                            "id": 15,
                            "province": 4,
                            "city": "0.1.4",
                            "name": "鞍山市",
                            "children": null
                        },
                        {
                            "id": 16,
                            "province": 4,
                            "city": "0.1.4",
                            "name": "抚顺市",
                            "children": null
                        }
                    ]
                }
            ]
        }
    ]
}

支持无限级联树，仅需要保证数据结构中id与province需要存在级联关系即可。