数据库取值新思路

原先

列表查询时，如果关联多张表，我会在sql中关联表进行查询

新思路

将不同的表，根据我所需要的字段进行查询，先放在对应的Map中，需要的时候从map中取值即可

// 封装品牌、分类、供货商查询信息
Set<Long> brandIds = Sets.newHashSet();
Set<Long> categoryIds = Sets.newHashSet();
Set<Long> supplierIds = Sets.newHashSet();
Set<Long> skuIds = Sets.newHashSet();
pages.getContent().forEach(item -> {
    brandIds.add(item.getBrandId());
    categoryIds.add(item.getCategoryId());
    categoryIds.add(item.getSubCategoryId());
    supplierIds.add(item.getSupplierId());
    skuIds.add(item.getSkuId());
});
Map<Long, Brand> brandMap = brandService.getBrandMap(brandIds);
Map<Long, Category> categoryMap = categoryService.getCategoryMap(categoryIds);
Map<Long, Supplier> supplierMap = supplierService.getSupplierMap(supplierIds);
Map<Long, Long> stockMap = storeSkuStockService.getSkuStockMap(Constants.YUN_CANG_ID, skuIds);
// 组装结果信息
    pages.getContent().forEach(item -> {
    SysStoreSkuDTO dto = new SysStoreSkuDTO();
    Supplier supplier = supplierMap.get(item.getSupplierId());
    if (supplier != null) {
        dto.setSupplierName(supplier.getSupplierName());
    }
    Long stock = stockMap.get(item.getSkuId());
    dto.setStock(stock == null ? 0 : stock);
    Brand brand = brandMap.get(item.getBrandId());
    dto.setBrandName(brand == null ? "" : brand.getBrandName());
    Category category = categoryMap.get(item.getCategoryId());
    Category subCategory = categoryMap.get(item.getSubCategoryId());
    dto.setCategoryName(category == null ? "" : category.getCategoryName());
    dto.setSubCategoryName(subCategory == null ? "" : subCategory.getCategoryName());
    dtoList.add(dto);
});