java-三级分类

 
    @Override
    public List listWithTree() {
        // 1 查出所有分类
        List entities = baseMapper.selectList(null);
        // 2 组装成父子的树形结构
        List level1Menus = entities.stream()
                .filter(categoryEntity -> categoryEntity.getParentCid() == 0 //通过ParentCid = 0找出一级分类
                ).map(item -> {
                    item.setChildren(getChrlidens(item, entities));//获取二级分类
                    return item;
                }).sorted((menu1,menu2)->{
                            return (menu1.getSort() == null?0:menu1.getSort()) - (menu2.getSort() == null?0:menu2.getSort());
                }).collect(Collectors.toList());
        return level1Menus;
    }

    //从allList中获取root子分类
    private List getChrlidens(CategoryEntity root, List allList) {
        List categoryTree = allList.stream()
                .filter(categoryEntity -> categoryEntity.getParentCid().equals(root.getCatId())//通过当前商品的父Id == 一级分类的ID查找子分类
                ).map(item -> {
                    item.setChildren(getChrlidens(item, allList));//获取三级分类
                    return item;
                }).sorted((menu1,menu2)->{
                    return (menu1.getSort() == null?0:menu1.getSort()) - (menu2.getSort() == null?0:menu2.getSort());
                }).collect(Collectors.toList());
        return categoryTree;
    }