树状结构转换工具类

项目中使用了很多树状结构，为了方便使用开发一个通用的工具类。

使用工具类的时候写一个类基础BaseNode，如果有个性化字段添加到类里面，然后就可以套用工具类。

工具类会将id和pid做关联返回一个树状结构的集合。

使用了hutool的工具包判空。

TreeUtil.java

import cn.hutool.core.util.ObjUtil;
import com.iccb.BaseNode;import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;public class TreeUtil {public static <T extends BaseNode<T>> List<T> toTree(List<T> treeNodeList) {//数据按照pid分组Map<Long, List<T>> map = treeNodeList.stream().collect(Collectors.groupingBy(T :: getPid,LinkedHashMap::new,Collectors.toList()));//找出所有的根节点，pid=-1的为根节点List<T> areaList = map.get(-1L);if(ObjUtil.isEmpty(areaList)){return new ArrayList<>();}for (T areaVO : areaList) {forEach(map, areaVO);}return areaList;}private static  <T extends BaseNode<T>> void forEach(Map<Long, List<T>> collect, T areaVO) {List<T> nodeList = collect.get(areaVO.getId());if (collect.get(areaVO.getId()) == null) {return;}areaVO.setChildren(nodeList);for (T node : nodeList) {forEach(collect, node);}}}

 BaseNode.java

import com.fasterxml.jackson.annotation.JsonFormat;
import lombok.Data;import java.io.Serializable;
import java.util.List;/*** @author admin*/
@Data
public class BaseNode<T> implements Serializable {private static final long serialVersionUID = 1L;@JsonFormat(shape = JsonFormat.Shape.STRING)private Long id;@JsonFormat(shape = JsonFormat.Shape.STRING)private Long pid;private String value;private List<T> children;
}

 使用范例

返回树状结构的地区数据

1）首先构建数据VO

@EqualsAndHashCode(callSuper = true)
@Data
public class AreaVO extends BaseNode<AreaVO> {private static final long serialVersionUID = 1L;private String areaCode;private String label;private String level;private String lnglat;}

2）查询地区数据

List<Area> list = areaService.list();

3) 构建数据VO 或者 直接使用mapper查询用VO封装

List<AreaVO> collect = list.stream().map(i -> {AreaVO areaVO = BeanUtil.copyProperties(i, AreaVO.class);areaVO.setLabel(i.getAreaName());areaVO.setValue(String.valueOf(i.getId()));areaVO.setLevel(i.getAreaLevel());areaVO.setPid(i.getParentId());return areaVO;
}).collect(Collectors.toList());

4) 使用工具类构造数据结构

List<AreaVO> areaTree = TreeUtil.toTree(collect);

数据返回示例

{"code": 200,"msg": null,"data": [{"id": "4058069977868140544","value": "4058069977868140544","pid": "4058069977868148888","children": [{"id": "4058069978245627904","value": "4058069978245627904","pid": "4058069977868140544","children": [{"id": "4058069978530840576","value": "4058069978530840576","pid": "4058069978245627904","children": null,"areaCode": "110101000000","label": "东城区","level": "3","lnglat": null},{"id": "4058069978732167168","value": "4058069978732167168","pid": "4058069978245627904","children": null,"areaCode": "110102000000","label": "西城区","level": "3","lnglat": null},{"id": "4058069978874773504","value": "4058069978874773504","pid": "4058069978245627904","children": null,"areaCode": "110105000000","label": "朝阳区","level": "3","lnglat": null},{"id": "4058069978979631104","value": "4058069978979631104","pid": "4058069978245627904","children": null,"areaCode": "110106000000","label": "丰台区","level": "3","lnglat": null},{"id": "4058069979046739968","value": "4058069979046739968","pid": "4058069978245627904","children": null,"areaCode": "110107000000","label": "石景山区","level": "3","lnglat": null},{"id": "4058069979118043136","value": "4058069979118043136","pid": "4058069978245627904","children": null,"areaCode": "110108000000","label": "海淀区","level": "3","lnglat": null},{"id": "4058069979231289344","value": "4058069979231289344","pid": "4058069978245627904","children": null,"areaCode": "110109000000","label": "门头沟区","level": "3","lnglat": null},{"id": "4058069979336146944","value": "4058069979336146944","pid": "4058069978245627904","children": null,"areaCode": "110111000000","label": "房山区","level": "3","lnglat": null},{"id": "4058069979441004544","value": "4058069979441004544","pid": "4058069978245627904","children": null,"areaCode": "110112000000","label": "通州区","level": "3","lnglat": null},{"id": "4058069979550056448","value": "4058069979550056448","pid": "4058069978245627904","children": null,"areaCode": "110113000000","label": "顺义区","level": "3","lnglat": null},{"id": "4058069979650719744","value": "4058069979650719744","pid": "4058069978245627904","children": null,"areaCode": "110114000000","label": "昌平区","level": "3","lnglat": null},{"id": "4058069979747188736","value": "4058069979747188736","pid": "4058069978245627904","children": null,"areaCode": "110115000000","label": "大兴区","level": "3","lnglat": null},{"id": "4058069979852046336","value": "4058069979852046336","pid": "4058069978245627904","children": null,"areaCode": "110116000000","label": "怀柔区","level": "3","lnglat": null},{"id": "4058069979956903936","value": "4058069979956903936","pid": "4058069978245627904","children": null,"areaCode": "110117000000","label": "平谷区","level": "3","lnglat": null},{"id": "4058069980166619136","value": "4058069980166619136","pid": "4058069978245627904","children": null,"areaCode": "110228000000","label": "密云区","level": "3","lnglat": null},{"id": "4058069980284059648","value": "4058069980284059648","pid": "4058069978245627904","children": null,"areaCode": "110229000000","label": "延庆区","level": "3","lnglat": null}],"areaCode": "110100000000","label": "北京市","level": "2","lnglat": null}],"areaCode": "110000000000","label": "北京市","level": "1","lnglat": null},{"id": "4058069980422471680","value": "4058069980422471680","pid": "4058069977868148888","children": [{"id": "4058069980527329280","value": "4058069980527329280","pid": "4058069980422471680","children": [{"id": "4058069980627992576","value": "4058069980627992576","pid": "4058069980527329280","children": null,"areaCode": "120101000000","label": "和平区","level": "3","lnglat": null},{"id": "4058069980732850176","value": "4058069980732850176","pid": "4058069980527329280","children": null,"areaCode": "120102000000","label": "河东区","level": "3","lnglat": null},{"id": "4058069980841902080","value": "4058069980841902080","pid": "4058069980527329280","children": null,"areaCode": "120103000000","label": "河西区","level": "3","lnglat": null},{"id": "4058069980938371072","value": "4058069980938371072","pid": "4058069980527329280","children": null,"areaCode": "120104000000","label": "南开区","level": "3","lnglat": null},{"id": "4058069981043228672","value": "4058069981043228672","pid": "4058069980527329280","children": null,"areaCode": "120105000000","label": "河北区","level": "3","lnglat": null},{"id": "4058069981148086272","value": "4058069981148086272","pid": "4058069980527329280","children": null,"areaCode": "120106000000","label": "红桥区","level": "3","lnglat": null},{"id": "4058069981252943872","value": "4058069981252943872","pid": "4058069980527329280","children": null,"areaCode": "120110000000","label": "东丽区","level": "3","lnglat": null},{"id": "4058069981357801472","value": "4058069981357801472","pid": "4058069980527329280","children": null,"areaCode": "120111000000","label": "西青区","level": "3","lnglat": null},{"id": "4058069981475241984","value": "4058069981475241984","pid": "4058069980527329280","children": null,"areaCode": "120112000000","label": "津南区","level": "3","lnglat": null},{"id": "4058069981580099584","value": "4058069981580099584","pid": "4058069980527329280","children": null,"areaCode": "120113000000","label": "北辰区","level": "3","lnglat": null},{"id": "4058069981684957184","value": "4058069981684957184","pid": "4058069980527329280","children": null,"areaCode": "120114000000","label": "武清区","level": "3","lnglat": null},{"id": "4058069981789814784","value": "4058069981789814784","pid": "4058069980527329280","children": null,"areaCode": "120115000000","label": "宝坻区","level": "3","lnglat": null},{"id": "4058069981890478080","value": "4058069981890478080","pid": "4058069980527329280","children": null,"areaCode": "120116000000","label": "滨海新区","level": "3","lnglat": null},{"id": "4058069981986947072","value": "4058069981986947072","pid": "4058069980527329280","children": null,"areaCode": "120117000000","label": "宁河区","level": "3","lnglat": null},{"id": "4058069982087610368","value": "4058069982087610368","pid": "4058069980527329280","children": null,"areaCode": "120118000000","label": "静海区","level": "3","lnglat": null},{"id": "4058069982293131264","value": "4058069982293131264","pid": "4058069980527329280","children": null,"areaCode": "120225000000","label": "蓟州区","level": "3","lnglat": null}],"areaCode": "120100000000","label": "天津市","level": "2","lnglat": null}],"areaCode": "120000000000","label": "天津市","level": "1","lnglat": null},{"id": "4461100398823866368","value": "4461100398823866368","pid": "4058069977868148888","children": [{"id": "4461100398974861312","value": "4461100398974861312","pid": "4461100398823866368","children": null,"areaCode": "820100000000","label": "澳门半岛","level": "2","lnglat": null},{"id": "4461100399113273344","value": "4461100399113273344","pid": "4461100398823866368","children": null,"areaCode": "820200000000","label": "离岛","level": "2","lnglat": null}],"areaCode": "820000000000","label": "澳门特别行政区","level": "1","lnglat": null}]
}

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