Dynamische Filterung mit JPA-Spezifikationen

public class ProductSpecifications {
    public static Specification<Product> hasCategory(String category) {
        return (root, query, cb) -> category == null ? null : cb.equal(root.get("category"), category);
    }
 
    public static Specification<Product> priceLessThan(Double price) {
        return (root, query, cb) -> price == null ? null : cb.lessThan(root.get("price"), price);
    }
}
 
// Usage in Service
List<Product> results = repository.findAll(Specification.where(hasCategory("Electronics")).and(priceLessThan(500.0)));