java後端操作樹結構
2023-10-23 15:00:43
一、樹結構的三種組裝方式(遞迴.雙層for迴圈,map)
（1）遞迴
普通遞迴方法
public Result getBmsMenuList(UserSessionVO userSessionInfo) {
// 查詢頂級節點選單
List<BmsMenuVO> bmsMenuVOList = bmsMenuDao.selectBmsMenuList(new BmsMenuQueryConditionVO());
for (BmsMenuVO bmsMenuVO : bmsMenuVOList) {
getBmsMenuListByRecursion(bmsMenuVO);
}
return Result.createWithModels(null, bmsMenuVOList);
}
private void getBmsMenuListByRecursion(BmsMenuVO bmsMenuVO) {
List<BmsMenuVO> bmsMenuVOS = bmsMenuDao.selectBmsMenuList(new BmsMenuQueryConditionVO().setParentId(bmsMenuVO.getId()));
if (CollectionUtils.isEmpty(bmsMenuVOS)) {
return;
}
bmsMenuVO.setChildBmsMenuList(bmsMenuVOS);
for (BmsMenuVO menuVO : bmsMenuVOS) {
getBmsMenuListByRecursion(menuVO);
}
}
stream流遞迴方法
//獲取父節點
List<TreeSelect> collect = trees.stream().filter(m -> m.getParentId() == 0).map(
(m) -> {
m.setChildren(getChildrenList(m, trees));
return m;
}
).collect(Collectors.toList());
/**
* 獲取子節點列表
* @param tree
* @param list
* @return
*/
public static List<TreeSelect> getChildrenList(TreeSelect tree, List<TreeSelect> list){
List<TreeSelect> children = list.stream().filter(item -> Objects.equals(item.getParentId(), tree.getId())).map(
(item) -> {
item.setChildren(getChildrenList(item, list));
return item;
}
).collect(Collectors.toList());
return children;
}
（2）雙層for迴圈
// 查詢主節點
List<BmsMenuVO> bmsMenuVOList = bmsRoleMenuDao.getAllRoleMenuList(condition);
// 拼裝結果
List<BmsMenuVO> bmsMenuTree = new ArrayList<>();
for (BmsMenuVO bmsMenuVO : bmsMenuVOList) {
// 根節點的父Id為null
if (bmsMenuVO.getParentId() == null) {
bmsMenuTree.add(bmsMenuVO);
}
for (BmsMenuVO menuVO : bmsMenuVOList) {
if (menuVO.getParentId() != null && menuVO.getParentId().equals(bmsMenuVO.getId())) {
if (CollectionUtils.isEmpty(bmsMenuVO.getChildBmsMenuList())) {
bmsMenuVO.setChildBmsMenuList(new ArrayList<>());
}
bmsMenuVO.getChildBmsMenuList().add(menuVO);
}
}
}
// 返回結果
return Result.createWithModels(null, bmsMenuTree);
（3）map遍歷
// 查詢所有節點
List<BmsMenuVO> bmsMenuVOList = bmsRoleMenuDao.getAllRoleMenuList(condition);
// 拼裝結果
List<BmsMenuVO> bmsMenuTree = new ArrayList<>();
// 用來儲存節點的子元素map
Map<Long, BmsMenuVO> childBmsMenuMap = new LinkedHashMap<>();
for (BmsMenuVO menuVO : bmsMenuVOList) {
childBmsMenuMap.put(menuVO.getId(), menuVO);
}
for (Long bmsMenuId : childBmsMenuMap.keySet()) {
BmsMenuVO menuVO = childBmsMenuMap.get(bmsMenuId);
Long parentId = menuVO.getParentId();
if (parentId == null) {
bmsMenuTree.add(menuVO);
} else {
BmsMenuVO parentMenuVO = childBmsMenuMap.get(parentId);
if (parentMenuVO.getChildBmsMenuList() == null) {
parentMenuVO.setChildBmsMenuList(new ArrayList<>());
}
parentMenuVO.getChildBmsMenuList().add(menuVO);
}
}
2、使用遞迴查詢某個節點所在的樹結構
使用場景：當我們得到一個樹形結構資料時，可能需要在樹形結構上對資料進行篩選，例如通過資料夾（檔案）名稱模糊查詢相關的資料夾並展現其父級。
缺點：需要查詢出完整的樹形結構才能用作篩選，在資料量非常龐大的時候並不適用。
@Data
public class TreeDto {
private String id;
private String name;
private List<TreeDto> subsetTreeDtoList;
public TreeDto(String id,String name,List<TreeDto> subsetTreeDtoList){
this.id = id;
this.name = name;
this.subsetTreeDtoList = subsetTreeDtoList;
}
}
篩選
/**
* 樹形篩選查詢
* @param treeDtoList 樹形集合
* @param idList 篩選條件(可以是其他條件)
* @return 包含的節點資料
*/
public static List<TreeDto> screenTree(List<TreeDto> treeDtoList, List<String> idList){
//最後返回的篩選完成的集合
List<TreeDto> screeningOfCompleteList = new ArrayList<>();
if (listIsNotEmpty(treeDtoList) && listIsNotEmpty(idList)){
for (TreeDto treeDto : treeDtoList){
List<TreeDto> subsetList = treeDto.getSubsetTreeDtoList();
//遞迴篩選完成後的返回的需要新增的資料
TreeDto addTreeDto = getSubsetPmsPlanPo(treeDto,subsetList,idList);
if (isNotEmpty(addTreeDto)){
screeningOfCompleteList.add(addTreeDto);
}
}
return screeningOfCompleteList;
}
return null;
}
/**
* 篩選符合的集合並返回
* @param treeDto 樹形類
* @param subsetTreeDtoList 子集集合
* @param idList 篩選條件
* @return 篩選成功的類
*/
public static TreeDto getSubsetPmsPlanPo(TreeDto treeDto,List<TreeDto> subsetTreeDtoList,List<String> idList){
//作為篩選條件的判斷值
String id = treeDto.getId();
//有子集時繼續向下尋找
if (listIsNotEmpty(subsetTreeDtoList)){
List<TreeDto> addTreeDtoList = new ArrayList<>();
for (TreeDto subsetTreeDto : subsetTreeDtoList){
List<TreeDto> subsetList = subsetTreeDto.getSubsetTreeDtoList();
TreeDto newTreeDto = getSubsetPmsPlanPo(subsetTreeDto,subsetList,idList);
//當子集篩選完不為空時新增
if (isNotEmpty(newTreeDto)){
addTreeDtoList.add(newTreeDto);
}
}
//子集滿足條件篩選時集合不為空時，替換物件集合內容並返回當前物件
if (listIsNotEmpty(addTreeDtoList)){
treeDto.setSubsetTreeDtoList(addTreeDtoList);
return treeDto;
//當前物件子集物件不滿足條件時，判斷當前物件自己是否滿足篩選條件，滿足設定子集集合為空，並返回當前物件
}else if (listIsEmpty(addTreeDtoList) && idList.contains(id)){
treeDto.setSubsetTreeDtoList(null);
return treeDto;
}else {
//未滿足篩選條件直接返回null
return null;
}
}else {
//無子集時判斷當前物件是否滿足篩選條件
if (idList.contains(id)){
return treeDto;
}else {
return null;
}
}
}
/**
* 判斷集合為空
* @param list 需要判斷的集合
* @return 集合為空時返回 true
*/
public static boolean listIsEmpty(Collection list){
return (null == list || list.size() == 0);
}
/**
* 判斷集合非空
* @param list 需要判斷的集合
* @return 集合非空時返回 true
*/
public static boolean listIsNotEmpty(Collection list){
return !listIsEmpty(list);
}
/**
* 判斷物件為null或空時
* @param object 物件
* @return 物件為空或null時返回 true
*/
public static boolean isEmpty(Object object) {
if (object == null) {
return (true);
}
if ("".equals(object)) {
return (true);
}
if ("null".equals(object)) {
return (true);
}
return (false);
}
/**
* 判斷物件非空
* @param object 物件
* @return 物件為非空時返回 true
*/
public static boolean isNotEmpty(Object object) {
if (object != null && !object.equals("") && !object.equals("null")) {
return (true);
}
return (false);
}
public static void main(String[] args) {
TreeDto treeDto1 = new TreeDto("1","A",new ArrayList<TreeDto>());
TreeDto treeDto1_1 = new TreeDto("1.1","A-A",new ArrayList<TreeDto>());
TreeDto treeDto1_2 = new TreeDto("1.2","A-B",new ArrayList<TreeDto>());
TreeDto treeDto1_3 = new TreeDto("1.3","A-C",new ArrayList<TreeDto>());
treeDto1.getSubsetTreeDtoList().add(treeDto1_1);
treeDto1.getSubsetTreeDtoList().add(treeDto1_2);
treeDto1.getSubsetTreeDtoList().add(treeDto1_3);
TreeDto treeDto2 = new TreeDto("2","B",new ArrayList<TreeDto>());
TreeDto treeDto2_1 = new TreeDto("2.1","B-A",new ArrayList<TreeDto>());
TreeDto treeDto2_2 = new TreeDto("2.2","B-B",new ArrayList<TreeDto>());
TreeDto treeDto2_3 = new TreeDto("2.3","B-C",new ArrayList<TreeDto>());
TreeDto treeDto2_3_1 = new TreeDto("2.3.1","B-C-A",null);
treeDto2.getSubsetTreeDtoList().add(treeDto2_1);
treeDto2.getSubsetTreeDtoList().add(treeDto2_2);
treeDto2.getSubsetTreeDtoList().add(treeDto2_3);
treeDto2.getSubsetTreeDtoList().get(2).getSubsetTreeDtoList().add(treeDto2_3_1);
String[] array = {"1.3","2.2","2.3.1"};
List<String> idList = Arrays.asList(array);
List<TreeDto> treeDtoList = new ArrayList<>();
treeDtoList.add(treeDto1);
treeDtoList.add(treeDto2);
System.out.println(JSON.toJSONString(screenTree(treeDtoList,idList)));
}
}
返回結果為
