前言：
在开发中，我们经常见到，前端展示树状结构的，这时候就需要后端去封装一个多级树结构对象，前端根据这样结构的数据去渲染数据，这篇文章讲的是如何封装成多级树结构对象。
正文：
1.先封装个树结构的对象
@Data
public class TreeDto {
private String id;
private String name;
private String pid;
private String isParent;
private List<TreeDto> childTreeDto; }
2.然后我把工具类代码粘贴下
public class TreeToolUtils {
private List<TreeDto> rootList; //根节点对象存放到这里
private List<TreeDto> bodyList; //其他节点存放到这里，可以包含根节点
public TreeToolUtils(List<TreeDto> rootList, List<TreeDto> bodyList) {
this.rootList = rootList;
this.bodyList = bodyList;
}
public List<TreeDto> getTree(){ //调用的方法入口
if(bodyList != null && !bodyList.isEmpty()){
//声明一个map，用来过滤已操作过的数据
Map<String,String> map = Maps.newHashMapWithExpectedSize(bodyList.size());
rootList.forEach(beanTree -> getChild(beanTree,map));
return rootList;
}
return null;
}
public void getChild(TreeDto treeDto,Map<String,String> map){
List<TreeDto> childList = Lists.newArrayList();
bodyList.stream()
.filter(c -> !map.containsKey(c.getId()))
.filter(c ->c.getPid().equals(treeDto.getId()))
.forEach(c ->{
map.put(c.getId(),c.getPid());
getChild(c,map);
childList.add(c);
});
treeDto.setChildTreeDto(childList);
}
}
3.然后写个main方法来测试下
TreeDto treeDto = new TreeDto("1", "总店", "null", "true",null);
TreeDto treeDto1 = new TreeDto("2", "市分店", "1", "true",null);
TreeDto treeDto2 = new TreeDto("3", "县分店", "2", "true",null);
TreeDto treeDto3 = new TreeDto("710", "店长", "3", "true",null);
TreeDto treeDto4= new TreeDto("713", "财务部", "3", "true",null);
TreeDto treeDto5 = new TreeDto("20032", "后勤部", "3", "true",null);
TreeDto treeDto6 = new TreeDto("1909", "小王", "710", "false",null);
TreeDto treeDto7= new TreeDto("1974", "小张", "713", "false",null);
TreeDto treeDto8 = new TreeDto("388187", "佳佳", "20032", "false",null);
TreeDto treeDto9 = new TreeDto("1949", "阿达", "20032", "false",null);
ArrayList<TreeDto> rootList = new ArrayList<>();//根节点
ArrayList<TreeDto> bodyList = new ArrayList<>();//子节点
rootList.add(treeDto);
bodyList.add(treeDto1);
bodyList.add(treeDto2);
bodyList.add(treeDto3);
bodyList.add(treeDto4);
bodyList.add(treeDto5);
bodyList.add(treeDto6);
bodyList.add(treeDto7);
bodyList.add(treeDto8);
bodyList.add(treeDto9);
TreeToolUtils utils = new TreeToolUtils(rootList,bodyList);
List<TreeDto> result = utils.getTree();
String jsonString = JSONObject.toJSONString(result.get(0));
System.out.println(jsonString);
}
4.最后控制台打印出的结果格式化后，就是这样的数据啦，前端根据层级去渲染数据就行啦
{
"childTreeDto": [{
"childTreeDto": [{
"childTreeDto": [{
"childTreeDto": [{
"childTreeDto": [],
"id": "1909",
"isParent": "false",
"name": "小王",
"pid": "710"
}],
"id": "710",
"isParent": "true",
"name": "店长",
"pid": "3"
}, {
"childTreeDto": [{
"childTreeDto": [],
"id": "1974",
"isParent": "false",
"name": "小张",
"pid": "713"
}],
"id": "713",
"isParent": "true",
"name": "财务部",
"pid": "3"
}, {
"childTreeDto": [{
"childTreeDto": [],
"id": "388187",
"isParent": "false",
"name": "佳佳",
"pid": "20032"
}, {
"childTreeDto": [],
"id": "1949",
"isParent": "false",
"name": "阿达",
"pid": "20032"
}],
"id": "20032",
"isParent": "true",
"name": "后勤部",
"pid": "3"
}],
"id": "3",
"isParent": "true",
"name": "县分店",
"pid": "2"
}],
"id": "2",
"isParent": "true",
"name": "市分店",
"pid": "1"
}],
"id": "1",
"isParent": "true",
"name": "总店",
"pid": "null"
}
原文：https://blog.csdn.net/jdk_wangtaida/article/details/87867620