SpringBoot查找多级商品方案【一次sql查询所有数据，循环处理分层逻辑】-Toy模板网

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一、查找所有商品

1、service

CategoryServiceImpl.java

/**
	 * 耗时：http(请求微信api) > 磁盘 > 内存
	 * mysql(内网+磁盘)
	 * @return
	 */
	@Override
	public ResponseVo<List<CategoryVo>> selectAll() {
		List<Category> categories = categoryMapper.selectAll();

		//查出parent_id=0
//		for (Category category : categories) {
//			if (category.getParentId().equals(ROOT_PARENT_ID)) {
//				CategoryVo categoryVo = new CategoryVo();
//				BeanUtils.copyProperties(category, categoryVo);
//				categoryVoList.add(categoryVo);
//			}
//		}

		//lambda + stream
		List<CategoryVo> categoryVoList = categories.stream()
				.filter(e -> e.getParentId().equals(ROOT_PARENT_ID))
				.map(this::category2CategoryVo)
				.sorted(Comparator.comparing(CategoryVo::getSortOrder).reversed())
				.collect(Collectors.toList());

		//查询子目录
		findSubCategory(categoryVoList, categories);

		return ResponseVo.success(categoryVoList);
	}

this::category2CategoryVo 等价于 e -> category2CategoryVo(e)

2、循环查找子目录

CategoryServiceImpl.java

private void findSubCategory(List<CategoryVo> categoryVoList, List<Category> categories) {
		for (CategoryVo categoryVo : categoryVoList) {
			List<CategoryVo> subCategoryVoList = new ArrayList<>();

			for (Category category : categories) {
				//如果查到内容，设置subCategory, 继续往下查
				if (categoryVo.getId().equals(category.getParentId())) {
					CategoryVo subCategoryVo = category2CategoryVo(category);
					subCategoryVoList.add(subCategoryVo);
				}

				subCategoryVoList.sort(Comparator.comparing(CategoryVo::getSortOrder).reversed());
				categoryVo.setSubCategories(subCategoryVoList);

				findSubCategory(subCategoryVoList, categories);
			}
		}
	}

3、直接拷贝数据

CategoryServiceImpl.java

	private CategoryVo category2CategoryVo(Category category) {
		CategoryVo categoryVo = new CategoryVo();
		BeanUtils.copyProperties(category, categoryVo);
		return categoryVo;
	}

二、根据categoryId查找多级商品

1、ProductServiceImpl.java

    @Override
    public ResponseVo<PageInfo> list(Integer categoryId, Integer pageNum, Integer pageSize) {
		Set<Integer> categoryIdSet = new HashSet<>();
		if (categoryId != null) {
            // 给categoryIdSet赋值子目categoryId
			categoryService.findSubCategoryId(categoryId, categoryIdSet);
			categoryIdSet.add(categoryId);
		}

		PageHelper.startPage(pageNum, pageSize);
		List<Product> productList = productMapper.selectByCategoryIdSet(categoryIdSet);
		List<ProductVo> productVoList = productList.stream()
				.map(e -> {
					ProductVo productVo = new ProductVo();
					BeanUtils.copyProperties(e, productVo);
					return productVo;
				})
				.collect(Collectors.toList());

		PageInfo pageInfo = new PageInfo<>(productList);
		pageInfo.setList(productVoList);
		return ResponseVo.success(pageInfo);
	}

2、CategoryServiceImpl.java文章来源地址https://www.toymoban.com/news/detail-651747.html

    @Override
	public void findSubCategoryId(Integer id, Set<Integer> resultSet) {
		List<Category> categories = categoryMapper.selectAll();
		findSubCategoryId(id, resultSet, categories);
	}

	private void findSubCategoryId(Integer id, Set<Integer> resultSet, List<Category> categories) {
		for (Category category : categories) {
			if (category.getParentId().equals(id)) {
				resultSet.add(category.getId());
				findSubCategoryId(category.getId(), resultSet, categories);
			}
		}
	}

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