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
}
]
}