java递归实现商品分类例子

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在对商品进行分类时，类别表会出现父节点

递归查询本节点的id及孩子节点的id

/**
 * 递归查询本节点的id及孩子节点的id
 * @param categoryId
 * @return
 */
public ServerResponse<List<Integer>> selectCategoryAndChildrenById(Integer categoryId){
    Set<Category> categorySet = Sets.newHashSet();
    findChildCategory(categorySet,categoryId);


    List<Integer> categoryIdList = Lists.newArrayList();
    if(categoryId != null){
        for(Category categoryItem : categorySet){
            categoryIdList.add(categoryItem.getId());
        }
    }
    return ServerResponse.createBySuccess(categoryIdList);
}


//递归算法,算出子节点
private Set<Category> findChildCategory(Set<Category> categorySet ,Integer categoryId){
    Category category = categoryMapper.selectByPrimaryKey(categoryId);
    if(category != null){
        categorySet.add(category);
    }
    //查找子节点,递归算法一定要有一个退出的条件
    List<Category> categoryList = categoryMapper.selectCategoryChildrenByParentId(categoryId);
    for(Category categoryItem : categoryList){
        findChildCategory(categorySet,categoryItem.getId());
    }
    return categorySet;
}