递归 操作

递归

案例一，菜单的递归

视频讲解

//获取全部菜单
    @Override
    public List<Permission> queryAllMenuGuli() {
        //1 查询菜单表所有数据
        QueryWrapper<Permission> wrapper = new QueryWrapper<>();
        wrapper.orderByDesc("id");
        List<Permission> permissionList = baseMapper.selectList(wrapper);
        //2 把查询所有菜单list集合按照要求进行封装
        List<Permission> resultList = bulidPermission(permissionList);
        return resultList;
    }

    //把返回所有菜单list集合进行封装的方法
    public static List<Permission> bulidPermission(List<Permission> permissionList) {

        //创建list集合，用于数据最终封装
        List<Permission> finalNode = new ArrayList<>();
        //把所有菜单list集合遍历，得到顶层菜单 pid=0菜单，设置level是1
        for(Permission permissionNode : permissionList) {
            //得到顶层菜单 pid=0是顶级菜单
            if("0".equals(permissionNode.getPid())) {
                //设置顶层菜单的level是1
                permissionNode.setLevel(1);
                //根据顶层菜单，向里面进行查询子菜单，封装到finalNode里面
                finalNode.add(selectChildren(permissionNode,permissionList));
            }
        }
        return finalNode;
    }

    private static Permission selectChildren(Permission permissionNode, List<Permission> permissionList) {
        //1 因为向一层菜单里面放二层菜单，二层里面还要放三层，把对象初始化
        permissionNode.setChildren(new ArrayList<Permission>());

        //2 遍历所有菜单list集合，进行判断比较，比较id和pid值是否相同
        for(Permission it : permissionList) {
            //判断 id和pid值是否相同
            if(permissionNode.getId().equals(it.getPid())) {
                //把父菜单的level值+1
                int level = permissionNode.getLevel()+1;
                it.setLevel(level);
                //如果children为空，进行初始化操作
                if(permissionNode.getChildren() == null) {
                    permissionNode.setChildren(new ArrayList<Permission>());
                }
                //把查询出来的子菜单放到父菜单里面
                permissionNode.getChildren().add(selectChildren(it,permissionList));
            }
        }
        return permissionNode;
    }

案例二，单位树

//构建单位树结构
Map<Long, List<SysOrg>> orgTree = new HashMap<>();
allManagerOrgIds.stream().forEach(x -> {
    List<SysOrg> buildChild = new ArrayList<>();
    List<SysOrg> topOrg = allChildOrgs.stream().filter(c -> c.getOrgId().equals(x)).collect(Collectors.toList());
    buildChild.addAll(topOrg);
    recursionFn(allChildOrgs, x, buildChild);
    orgTree.put(x, buildChild);
});

//递归操作
private void recursionFn(List<SysOrg> allChildList, Long parentOrgId, List<SysOrg> newChildList) {
        allChildList.stream().filter(x -> x.getParentId().equals(parentOrgId)).collect(Collectors.toList()).forEach(y -> {
                newChildList.add(y);
                recursionFn(allChildList, y.getOrgId(), newChildList);
        });
    }```