👀 Views: 0 💬 Answers: 1 📅 Created: 2025-06-16

spring-boot rest spring-data-jpa pagination specifications Java

I'm working on a personal project and I'm working on a project and hit a roadblock. I'm building a Spring Boot REST API for a product catalog where I need to support searching products using multiple query parameters like `category`, `brand`, and `priceRange`. Additionally, I want to implement pagination to improve performance and user experience. However, I'm struggling with how to effectively handle these query parameters together. For example, I want the endpoint to look something like this: `/products?category=electronics&brand=samsung&priceRange=100-500&page=1&size=10`. I've set up my controller method like this: ```java @GetMapping("/products") public ResponseEntity<List<Product>> getProducts( @RequestParam(required = false) String category, @RequestParam(required = false) String brand, @RequestParam(required = false) String priceRange, @RequestParam(defaultValue = "0") int page, @RequestParam(defaultValue = "10") int size) { // Logic to filter and paginate products } ``` I also have a service method that retrieves the products from the database, which uses a `Pageable` object to enable pagination, like so: ```java public Page<Product> findProducts(String category, String brand, String priceRange, Pageable pageable) { // Implementation for filtering by category, brand, and price range } ``` However, I'm not sure how to structure the filtering logic in the repository layer to accommodate the multiple filter criteria. I'm using Spring Data JPA and would like to leverage the `Specification` API for this purpose. I've attempted to create a `Specification<Product>` to handle this, but I'm running into issues when the parameters are optional. For instance, I don't want to apply any filters if their respective parameters are null. Here's what I have so far for the specification: ```java public class ProductSpecifications { public static Specification<Product> hasCategory(String category) { return (root, query, criteriaBuilder) -> { if (category == null) return criteriaBuilder.conjunction(); return criteriaBuilder.equal(root.get("category"), category); }; } // Similar methods for brand and price range } ``` But when I combine these specifications in my repository, it doesn't seem to filter as expected, especially when one of the parameters is not provided. I'm getting a list of products that do not match the criteria or even empty results when I know there should be matches. Any guidance on how to effectively combine these specifications and ensure that pagination works correctly would be greatly appreciated. Thanks! This is part of a larger API I'm building. What am I doing wrong?