Java后台组装树形结构数据

一张表的自关联存储,后台一次性查询出所有数据,再进行组装

 public List<CpLbTreeDto> treeList() {
     
        List<CpLbTreeDto> cpLbTreeDtoList = cpLbDao.treeList();
        return buildTree(cpLbTreeDtoList);
 }

/**
     * 组装树
     * 查询出的数据是按照层级倒序排列,结果集合中子级在上,父级在下;
     * 将查到的数据循环放入LinkedHashMap中,
     * 再循环该map,从子级开始组装数据,根据子级的父节点code从map中取出其父节点,
     * 并将该子节点纳入到其父节点的子节点中
     *
     * @param list
     * @return
     */
    private List<CpLbTreeDto> buildTree(List<CpLbTreeDto> list) {
     
        if (!CollectionUtils.isEmpty(list)) {
     
            Map<String, CpLbTreeDto> treeDtoTempMap = new LinkedHashMap<>(list.size());
            for (CpLbTreeDto menu : list) {
     
                treeDtoTempMap.put(menu.getCode(), menu);
            }
            //root节点
            CpLbTreeDto root = new CpLbTreeDto();
            root.setName("root");
            for (CpLbTreeDto treeDto : treeDtoTempMap.values()) {
     
                if (Objects.equals("1", treeDto.getClassLevel())
                        || treeDto.getCode().equals(treeDto.getParentCode())
                        || treeDto.getCode().equals(treeDto.getTopCode())) {
     
                    //如果该节点是父节点
                    List<CpLbTreeDto> rootChildren = root.getChildren();
                    if (rootChildren == null) {
     
                        rootChildren = new ArrayList<>();
                    }
                    rootChildren.add(treeDto);
                    root.setChildren(rootChildren);
                } else {
     
                    //如果该节点是子节点
                    CpLbTreeDto cpLbTreeDtoParent = treeDtoTempMap.get(treeDto.getParentCode());
                    List<CpLbTreeDto> parentChildren = cpLbTreeDtoParent.getChildren();
                    if (parentChildren == null) {
     
                        parentChildren = new ArrayList<>();
                    }
                    parentChildren.add(treeDto);
                    cpLbTreeDtoParent.setChildren(parentChildren);
                }
            }
            return root.getChildren();
        }
        return null;
    }