树形结构转换工具类

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。

<dependency><groupId>cn.hutool</groupId><artifactId>hutool-all</artifactId><version>5.8.25</version>
</dependency>

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);

返回数据示例

查看代码

 {"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": "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": "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": "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": "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}],"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}]
}