Java根据子节点获取最上层节点(根节点)数据和所有上级集合

你的名字 2024-04-08 09:30 63阅读 0赞

**目录**

1 通过递归获取树形结构、通过父节点获取最底层节点(叶子节点)数据、树形XML，可以参考以下内容：

2 实体和数据结构

2.1 Dept实体类

2.2 相关树形结构

3 根据子节点获取最上层节点(根节点)数据

3.1 service层

3.2 controller层

3.3 测试

4 根据子节点获取所有上级集合

4.1 service层

4.2 controller层

4.3 测试

--------------------

### 1 通过递归获取树形结构、通过父节点获取最底层节点(叶子节点)数据、树形XML，可以参考以下内容： ###

[Java树形结构 根据父节点获取最底层节点数据 树形xml\_www\_48568302的博客-CSDN博客][Java_ _ _xml_www_48568302_-CSDN]

### 2 实体和数据结构 ###

#### 2.1 Dept实体类 ####

/**
     * @author W
     * @createDate 2022/8/10
     * @description: Dept实体类
     */
    @Data
    @AllArgsConstructor
    @NoArgsConstructor
    public class Dept {
        private String id;
        private String name;
        private String parentId;
        private List<Dept> children = new ArrayList<>(); // 可不要
    }

#### 2.2 相关树形结构 ####

![42676a783eca498cb49f00ae32a27746.png][]

### 3 根据子节点获取最上层节点(根节点)数据 ###

#### 3.1 service层 ####

*  **方法一：根据根节点的parentId="0"进行判断递归**

/**
         * 根据子节点获取最上层节点
         * @param deptAll 所有部门集合
         * @param deptChild 子节点
         * @return
         */
        public static Dept getMaximumParent(List<Dept> deptAll, Dept deptChild){
            Dept dept = null;
            String parentId = deptChild.getParentId();
            if(parentId.equals("0")){
                dept = deptChild;
            }else {
                List<Dept> parent = deptAll.stream().filter(item -> item.getId().equals(parentId)).collect(Collectors.toList());
                Dept maximumParent = getMaximumParent(deptAll, parent.get(0));
                dept = maximumParent;
            }
            return dept;
        }

*  **方法二：递归至上层节点为 null 返回入参的子节点数据为根节点**

/**
         * 根据子节点获取最上层节点
         * @param deptAll 所有部门集合
         * @param deptChild 子节点
         * @return
         */
        public static Dept getMaximumParent2(List<Dept> deptAll, Dept deptChild) {
            if(ObjectUtil.isNotEmpty(deptChild)){
                String parentId = deptChild.getParentId();
                List<Dept> parentDepts = deptAll.stream().filter(item -> item.getId().equals(parentId)).collect(Collectors.toList());
                if(CollectionUtil.isNotEmpty(parentDepts)){
                    Dept parentDept = parentDepts.get(0);
                    Dept maximumParent2 = getMaximumParent2(deptAll, parentDept);
                    if(maximumParent2==null){
                        return parentDept;
                    }
                    return maximumParent2;
                }
            }
            return null;
        }

**踩坑**，通过索引获取空集合元素，会报IndexOutOfBoundsException下标越界异常，代码如下：

![39bb1b98f6ac4b4ba995d981a617228d.png][]

报错信息，如下：

![cc890a9118934213b67b378c4b81864b.png][]

#### 3.2 controller层 ####

@GetMapping("/getMaximumParent2")
    public ResponseResult getMaximumParent2(){
        List<Dept> deptAll = GetLeafNode.getDeptAll(); // 所有部门集合
        Dept leafNodeDept = new Dept("322","四层8","32",null);
        Dept deptRoot = GetLeafNode.getMaximumParent2(deptAll, leafNodeDept);
        return ResponseResult.success("根据子节点获取根节点",deptRoot);
    }

#### 3.3 测试 ####

![2c52a1d56bbe41a2b4922faf49fc34cf.png][]

### 4 根据子节点获取所有上级集合 ###

#### 4.1 service层 ####

/**
     * 向上查询所有上级
     * @param deptAll 所有集合
     * @param leafNodeDept 叶子节点
     */
    public static Set<Dept> getDeptUpList(List<Dept> deptAll,Dept leafNodeDept){
        if(ObjectUtil.isNotEmpty(leafNodeDept)){
            Set<Dept> set = new HashSet<>();
            String parentId = leafNodeDept.getParentId();
            List<Dept> parentDepts = deptAll.stream().filter(item -> item.getId().equals(parentId)).collect(Collectors.toList());
            if(CollectionUtil.isNotEmpty(parentDepts)){
                Dept parentDept = parentDepts.get(0);
                set.add(parentDept);
                Set<Dept> deptUpTree = getDeptUpList(deptAll, parentDept);
                if(deptUpTree!=null){
                    set.addAll(deptUpTree);
                }
                return set;
            }
        }
        return null;
    }

#### 4.2 controller层 ####

@GetMapping("/getDeptUpList")
    public ResponseResult getDeptUpTree(){
        List<Dept> deptAll = GetLeafNode.getDeptAll(); // 所有部门集合
        Dept leafNodeDept = new Dept("322","四层8","32",null);
        Set<Dept> deptUpTree = GetLeafNode.getDeptUpList(deptAll, leafNodeDept);
        return ResponseResult.success("根据子节点查出的所有上级",deptUpTree);
    }

#### 4.3 测试 ####

![e9c4a4e5147a44efa2bf6d0887556a90.png][]

[Java_ _ _xml_www_48568302_-CSDN]: https://blog.csdn.net/weixin_48568302/article/details/126273963
[42676a783eca498cb49f00ae32a27746.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/08/93fbe5f4b1a648e1bb878d1eaff09d63.png
[39bb1b98f6ac4b4ba995d981a617228d.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/08/428f85a6b6ad40c4bd67896269b41f9d.png
[cc890a9118934213b67b378c4b81864b.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/08/84de2ea17c434a4388cb42aa379b1e30.png
[2c52a1d56bbe41a2b4922faf49fc34cf.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/08/6e5a214402784a818699b1d33efc7305.png
[e9c4a4e5147a44efa2bf6d0887556a90.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/08/c279671ba8f54706bdb28008dafc9b43.png