根据层级关系，构建树形结构数据

╰+哭是因爲堅強的太久メ 2023-06-25 03:04 46阅读 0赞

### 根据层级关系，构建树形结构数据 ###

*   *  一、基本模型
     *  二、递归工具类
     *  三、基于Model数据，构建资源树

## 一、基本模型 ##

@Data
    public class ResourceTreeVO { 
    
        private Long resourceId;
        /** * 资源级别 * 1：一级,2：二级,3：三级 */
        private Integer level;
        /** * 资源名称 */
        private String name;
        /** * 父级ID */
        private Long parentId;
        /** * 权限标识 */
        private String code;
        /** * 子列表 */
        private List<ResourceTreeVO> children;
    
    
        public ResourceTreeVO(Resource resource) { 
            this.resourceId = resource.getResourceId();
            this.level = resource.getLevel();
            this.name = resource.getName();
            this.parentId = resource.getParentId();
            this.code = resource.getCode();
            this.children = null;
        }
    
        public ResourceTreeVO() { 
        }
    }

如何基于这个Model数据，构建树？

## 二、递归工具类 ##

public class ResourceTreeUtil { 
        private List<ResourceTreeVO> rootList; //根节点对象存放到这里
        private List<ResourceTreeVO> bodyList; //其他节点存放到这里
        public ResourceTreeUtil(List<ResourceTreeVO> rootList, List<ResourceTreeVO> bodyList) { 
            this.rootList = rootList;
            this.bodyList = bodyList;
        }
    
        // 构建Tree方法调用
        public List<ResourceTreeVO> getTree() { 
            if (bodyList != null && !bodyList.isEmpty()) { 
                // 声明 map，用来过滤已操作过的数据
                Map<Long, Long> map = Maps.newHashMapWithExpectedSize(bodyList.size());
                rootList.forEach(beanTree -> getChild(beanTree, map));
                return rootList;
            }
            return null;
        }
    
        // 递归实现获取子集
        public void getChild(ResourceTreeVO beanTree, Map<Long, Long> map) { 
            List<ResourceTreeVO> childList = Lists.newArrayList();
            bodyList.stream()
                    .filter(c -> !map.containsKey(c.getResourceId()))
                    .filter(c -> c.getParentId().equals(beanTree.getResourceId()))
                    .forEach(c -> { 
                        map.put(c.getResourceId(), c.getParentId());
                        getChild(c, map);
                        childList.add(c);
                    });
            beanTree.setChildren(childList);
        }
    
    }

## 三、基于Model数据，构建资源树 ##

public List<ResourceTreeVO> ListTree() { 
            List<ResourceTreeVO> treeVOList = this.list(null).stream().map(ResourceTreeVO::new).collect(Collectors.toList());
            // 先找到根节点
            List<ResourceTreeVO> rootList = treeVOList.stream()
                    .filter(e -> ResourceLevelEnum.FIRST_LEVEL.getLevel().equals(e.getLevel()))
                    .collect(Collectors.toList());
            // 子节点元数据
            List<ResourceTreeVO> bodyList = treeVOList.stream()
                    .filter(e -> !ResourceLevelEnum.FIRST_LEVEL.getLevel().equals(e.getLevel()))
                    .collect(Collectors.toList());
    
            ResourceTreeUtil treeUtil = new ResourceTreeUtil(rootList, bodyList);
            return treeUtil.getTree();
        }