Java 新手。在我的項目中，我通過 findAll(spec) 獲取數據，如下所示：public interface ProductRepository extends JpaRepository<Product, Long> { List<Product> findAll(Specification<Product> spec);在控制器中，我將響應轉換為 DTO，如下所示：（ProductResponse 是一個 DTO）private List<ProductResponse> convertProductListToResponse(List<Product> products) { List<ProductResponse> productResponseList = new ArrayList<ProductResponse>(); for(int i = 0; i < products.size(); i++) { ProductResponse productResponse = new ProductResponse(); productResponse.convert(products.get(i)); productResponseList.add(productResponse); } return productResponseList;}@PostMapping("getProducts/{page}")public List<ProductResponse> getAllProducts(@PathVariable("page") int page) { ProductSpecification nameSpecification = new ProductSpecification(new SearchCriteria("title", ":", "First Product")); // Service simply uses repository method: List<Product> filterProducts = productService.findAll(Specification.where(nameSpecification)); List<ProductResponse> productResponseList = this.convertProductListToResponse(filterProducts); return productResponseList;}然后我決定通過分頁獲取數據，所以我更改了存儲庫：public interface ProductRepository extends PagingAndSortingRepository<Product, Long> { List<Product> findAll(Specification<Product> spec, Pageable pageable);現在我收到以下錯誤：java.lang.ClassCastException: org.springframework.data.domain.PageImpl cannot be cast to com.vendo.app.entity.Product然后我直接在控制器中輸出響應（filterProducts），并發現響應結構如下：[ { "content": [ { "id": 1, "deleted": false, "title": "First Product", ... ....// array of product objects我實在不明白，響應類型為List的方法怎么會返回這樣的響應？如何從此響應中獲取產品列表并將其轉換為 DTO？
3 回答
子衿沉夜
TA貢獻1828條經驗 獲得超3個贊
基本上默認findAll有 2 個變體
如果您想轉換Page<Product>為簡單List<Product>
productRepository.findAll(PageRequest.of(0, count)).toList();
躍然一笑
TA貢獻1826條經驗 獲得超6個贊
我意識到我的錯誤是使用 List 而不是 Page 作為 findAll 的返回類型。
存儲庫應如下所示：
??Page<Product>?findAll(Specification<Product>?spec,?Pageable?pageable);
控制器應如下所示：
????@PostMapping("getProducts/{page}")public?List<ProductResponse>?getAllProducts(@PathVariable("page")?int?page)?{?
???????Pageable?productPageable?=?PageRequest.of(0,?page);
???????????ProductSpecification?nameSpecification?=?new?ProductSpecification(new?SearchCriteria("title",?":",?"First?Product"));
????Page<Product>?filterProducts?=?productService.findAll(Specification.where(nameSpecification),?productPageable);
????List<ProductResponse>?productResponseList?=?this.convertProductListToResponse(filterProducts.getContent());?
???????return?productResponseList;
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