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When building sophisticated REST APIs, dynamic filtering is a game-changer. It allows API consumers to tailor their requests by applying various filters to the data they need. When paired with pagination, dynamic filtering can manage large datasets efficiently while providing flexibility for end users. By combining Spring Boot, JPA, and PostgreSQL, you have all the tools needed to implement this powerful functionality seamlessly.

This guide will walk you through creating a robust API that supports dynamic filtering and pagination, complete with examples and performance optimization techniques.

What is Dynamic Filtering?
Pagination + Filter: Real-World Use Case
Define Filters Using @RequestParam
Combine Filters in Service Layer
Using JpaSpecificationExecutor
Dynamic Query with CriteriaBuilder
Pass Filters with Pagination + Sort
Example Endpoint: GET /products?brand=Apple&page=0
Optimize Dynamic Queries for PostgreSQL
Final Working Code Walkthrough
FAQs

What is Dynamic Filtering?

Dynamic filtering is the ability to apply flexible filters to API endpoints based on user-specified conditions, such as brand, category, or priceRange. Unlike hardcoded queries, dynamic filtering adjusts query logic at runtime depending on the API request parameters.

For example, an e-commerce API might allow users to filter products by multiple criteria such as brand, price range, and availability. This functionality allows users to retrieve targeted results, reducing the amount of unnecessary data transferred between the server and client.

Benefits of Dynamic Filtering

Customizable Data Retrieval: Adapt queries to specific user needs.
Improved Performance: Eliminate unnecessary rows in responses.
Scalability: Easily extend filters as the application evolves.

Dynamic filtering becomes even more useful when paired with pagination to manage large datasets effectively.

Pagination + Filter: Real-World Use Case

Imagine an online store with millions of products. Without pagination and filtering, querying the entire product inventory would overwhelm the database and slow down the user experience. Adding pagination allows users to browse 10–20 items at a time, and filtering ensures users only see relevant products.

Use Case:

Request: A user searches for products by brand (Apple), price (>1000), and category (Laptops).
Response: Return paginated results (e.g., 10 items per page) sorted by relevance or price.

By combining filtering and pagination, you can guarantee users receive fast, meaningful data with minimal resource consumption.

Define Filters Using @RequestParam

Spring Boot makes it easy to collect query parameters using @RequestParam. These parameters represent the filter criteria passed by the user in an HTTP request.

Example:

@GetMapping("/products")
public List<Product> getProducts(
    @RequestParam(required = false) String brand,
    @RequestParam(required = false) String category,
    @RequestParam(required = false) Double minPrice,
    @RequestParam(required = false) Double maxPrice
) {
    // Logic to filter products
}

Explanation:

The required = false flag allows parameters to be optional.
Users can pass any combination of parameters, enabling dynamic filtering.

Combine Filters in Service Layer

Filters are typically combined in the service layer using conditional logic. This prevents the controller from becoming bloated and difficult to maintain.

Example Service Method:

public List<Product> getFilteredProducts(String brand, String category, Double minPrice, Double maxPrice) {
    if (brand != null) {
        // Add logic to filter by brand
    }
    if (category != null) {
        // Add logic to filter by category
    }
    // Continue aggregating filters
    return productRepository.findFilteredProducts(brand, category, minPrice, maxPrice);
}

This approach allows scalability, letting you add more filters easily.

Using JpaSpecificationExecutor

Spring Data JPA provides a JpaSpecificationExecutor interface for creating dynamic, type-safe queries. It allows you to define reusable specifications (conditions) to build queries dynamically.

Example Specification:

public class ProductSpecifications {
    public static Specification<Product> hasBrand(String brand) {
        return (root, query, criteriaBuilder) -> {
            if (brand == null) return null;
            return criteriaBuilder.equal(root.get("brand"), brand);
        };
    }
}

Adding Multiple Specifications:

Specification<Product> spec = Specification.where(hasBrand(brand))
                                           .and(hasCategory(category))
                                           .and(hasPriceRange(minPrice, maxPrice));

These specifications are combined seamlessly to build dynamic queries.

Dynamic Query with CriteriaBuilder

For more control over dynamic queries, you can use JPA’s CriteriaBuilder API. This API lets you construct complex queries programmatically.

Example Query:

public List<Product> findWithDynamicFilters(String brand, String category, Double minPrice, Double maxPrice) {
    CriteriaBuilder cb = entityManager.getCriteriaBuilder();
    CriteriaQuery<Product> query = cb.createQuery(Product.class);
    Root<Product> root = query.from(Product.class);

    List<Predicate> predicates = new ArrayList<>();
    if (brand != null) {
        predicates.add(cb.equal(root.get("brand"), brand));
    }
    if (minPrice != null && maxPrice != null) {
        predicates.add(cb.between(root.get("price"), minPrice, maxPrice));
    }

    query.where(predicates.toArray(new Predicate[0]));
    return entityManager.createQuery(query).getResultList();
}

Pass Filters with Pagination + Sort

To send filtering, pagination, and sorting data together, use the following approach:

API Request Example:

GET /products?brand=Apple&category=Laptops&minPrice=1000&sort=price,asc&page=0&size=20

Controller Update:

@GetMapping("/products")
public Page<Product> getProducts(
    @RequestParam Map<String, String> filters,
    Pageable pageable
) {
    Specification<Product> spec = buildSpecifications(filters);
    return productRepository.findAll(spec, pageable);
}

Filters and pagination parameters seamlessly combine into a single API call.

Example Endpoint: GET /products?brand=Apple&page=0

Here’s what a dynamic filtering endpoint might look like:

Implementation:

@GetMapping("/products")
public Page<Product> getFilteredProducts(
    @RequestParam(required = false) String brand,
    @RequestParam(required = false) Double minPrice,
    Pageable pageable
) {
    Specification<Product> spec = Specification.where(
        ProductSpecifications.hasBrand(brand))
        .and(ProductSpecifications.hasPriceGreaterThan(minPrice));

    return productRepository.findAll(spec, pageable);
}

Example Request:

GET /products?brand=Apple&page=0&size=5

This returns a paginated and filtered product list.

Optimize Dynamic Queries for PostgreSQL

For large datasets, optimize queries with the following techniques:

Indexes: Create indexes on frequently queried fields like brand or price.
Batch Fetching: Use Hibernate’s batch size setting to fetch related entities in batches.
EXPLAIN Queries: Analyze query performance using PostgreSQL’s EXPLAIN functionality.

These optimizations reduce query execution time and improve API response times.

Final Working Code Walkthrough

Product Entity:

@Entity
public class Product {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private String brand;
    private double price;

    // Getters and setters
}

JpaRepository:

@Repository
public interface ProductRepository extends JpaRepository<Product, Long>, JpaSpecificationExecutor<Product> {
}

Controller:

@GetMapping("/products")
public Page<Product> getFilteredProducts(
    @RequestParam(required = false) String brand,
    @RequestParam(required = false) Double minPrice,
    Pageable pageable
) {
    Specification<Product> spec = Specification.where(
        ProductSpecifications.hasBrand(brand))
        .and(ProductSpecifications.hasPriceGreaterThan(minPrice));

    return productRepository.findAll(spec, pageable);
}

FAQs

Q1. What is JpaSpecificationExecutor used for?

It allows creating type-safe, dynamic queries by combining various query conditions at runtime.

Q2. How do I optimize dynamic queries for PostgreSQL?

Use indexes, batch fetching, and PostgreSQL’s EXPLAIN to analyze and optimize query plans.

Q3. Can pagination and sorting work with filtering?

Yes, Spring Data JPA integrates pagination, sorting, and filtering seamlessly in one API call.

Dynamic filtering with pagination enables efficient, flexible, and performant APIs. With this guide, you’re now ready to build next-level APIs using Spring Boot, PostgreSQL, and JPA!

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