@Override
    public ServerResponse<PageInfo> getProductByKeywordCategory(String keyword , Integer categoryId , int pageNum , int pageSize , String orderBy){
        if(StringUtils.isBlank(keyword) && categoryId == null){
            return ServerResponse.createByErrorCodeMessage(ResponseCode.ILLEGAL_ARGUEMENT.getCode() , ResponseCode.ILLEGAL_ARGUEMENT.getDesc());
        }
        //如果查询的是父级产品时，要呈现出子级别产品
        List<Integer> categoryList = new ArrayList<>();
        if(categoryId != null){
            Category category = categoryMapper.selectByPrimaryKey(categoryId);
            if(category == null && StringUtils.isNotBlank(keyword)){
                //没有该分类，并且没有关键字，但是没有错误
                PageHelper.startPage(pageNum , pageSize);
                List<ProductDetailVo> productDetailVoList = newArrayList();
                //传入空的list
                PageInfo pageInfo = new PageInfo(productDetailVoList);
                return ServerResponse.createBySuccess(pageInfo);
            }
            categoryList = iCategoryService.selectCategoryAndChildrenById(category.getId()).getData();
        }
        if(StringUtils.isNotBlank(keyword)){
            keyword = new StringBuilder().append("%").append(keyword).append("%").toString();
        }
        PageHelper.startPage(pageNum , pageSize);
        //排序处理
        if(StringUtils.isNotBlank(orderBy)){
            if(Const.ProductListOrderBy.PRICE_ASC_DESC.contains(orderBy)){
                //根据"_"符号，将orderByArray分割
                String[] orderByArray = orderBy.split("_");
                PageHelper.orderBy(orderByArray[0] + " " + orderByArray[1]);
            }
        }
        List<Product> productList = productMapper.selectByNameAndCategoryIds(StringUtils.isBlank(keyword) ? null : keyword, categoryList.size() == 0 ? null : categoryList);
        System.out.println(productList);
        List<ProductListVo> productDetailVoList =  Lists.newArrayList();
        for(Product product : productList){
            ProductListVo productListVo = assembleProductListVo(product);
            productDetailVoList.add(productListVo);
        }

        System.out.println(productDetailVoList);
        PageInfo pageInfo = new PageInfo(productList);
        pageInfo.setList(productDetailVoList);

        return ServerResponse.createBySuccess(pageInfo);


    }
老师我这个查出来怎么productDetailVoList一直为空

这个输出的是productList，只有page的，也没有显示数据库中查到的东西
Page{count=true, pageNum=0, pageSize=10, startRow=0, endRow=0, total=3, pages=1, countSignal=true, orderBy='price desc', 

orderByOnly=false, reasonable=false, pageSizeZero=false}

~~~xml
 <select id="selectByNameAndCategoryIds" resultMap="BaseResultMap" parameterType="map">
    SELECT
    <include refid="Base_Column_List"></include>
    from mmall_product
    where status = 1
    <if test="productName != null">
      and name like #{productName}
    </if>
    <if test="categoryIdList != null" >
      and category_id in
      <foreach item="item" index="index" open="(" separator="," close=")" collection="categoryIdList">
        #{item}
      </foreach>
    </if>
  </select>