Optional @RequestParam with defaultValue in Spring MVC

Direct Answer

Set required=false when absence should be represented as null for a nullable/reference type, use Optional<T> when explicit absence helps, or provide defaultValue when the endpoint has a real fallback. A default value implicitly makes @RequestParam non-required. Prefer a default for primitive parameters because primitives cannot represent null.

Code Example

@RestController
@RequestMapping("/api/products")
public class ProductController {

    private final ProductRepository productRepository;

    public ProductController(ProductRepository productRepository) {
        this.productRepository = productRepository;
    }

    @GetMapping
    public List<Product> searchProducts(
            @RequestParam(required = false) String category,
            @RequestParam(required = false) String name,
            @RequestParam(defaultValue = "0") int page,
            @RequestParam(defaultValue = "20") int size,
            @RequestParam(defaultValue = "name") String sortBy) {
        // All these work:
        // GET /api/products -> defaults: page=0, size=20, sortBy=name, category=null, name=null
        // GET /api/products?category=electronics
        // GET /api/products?page=2&size=10&sortBy=price
        return productRepository.findProducts(category, name, page, size, sortBy);
    }
}

Common Mistakes & Pitfalls

• No defaults for pagination: Freshers write @RequestParam int page, @RequestParam int size without defaultValue, forcing clients to always specify pagination. This makes simple requests like GET /users fail with 400. Always provide defaults for page (usually 0) and size (usually 10 or 20).
• Using empty string as default: Writing @RequestParam(defaultValue="") String name means name is never null, it's an empty string when omitted. This can break repository queries that check if (name != null). Use required=false instead and handle null explicitly.
• Primitive types with required=false: Writing @RequestParam(required=false) int page doesn't work — primitives can't be null. Spring will throw an error if the parameter is missing. Use Integer (boxed type) instead: @RequestParam(required=false) Integer page, or use defaultValue with the primitive type.