Building REST Controllers

@RestController
@RequestMapping("/api/v1/products")
public class ProductController {

    private final ProductService productService;

    public ProductController(ProductService productService) {
        this.productService = productService;
    }

    @GetMapping
    public List<ProductDto> getAllProducts() {
        return productService.findAll();
    }

    @GetMapping("/{id}")
    public ProductDto getProduct(@PathVariable String id) {
        return productService.findById(id);
    }

    @PostMapping
    @ResponseStatus(HttpStatus.CREATED)
    public ProductDto createProduct(@RequestBody @Valid CreateProductRequest request) {
        return productService.create(request);
    }

    @PutMapping("/{id}")
    public ProductDto updateProduct(@PathVariable String id,
                                    @RequestBody @Valid UpdateProductRequest request) {
        return productService.update(id, request);
    }

    @DeleteMapping("/{id}")
    @ResponseStatus(HttpStatus.NO_CONTENT)
    public void deleteProduct(@PathVariable String id) {
        productService.delete(id);
    }
}

// GET /products?category=electronics&page=0&size=20
@GetMapping
public Page<ProductDto> getProducts(
        @RequestParam(required = false) String category,
        @RequestParam(defaultValue = "0") int page,
        @RequestParam(defaultValue = "20") int size) {
    return productService.findAll(category, PageRequest.of(page, size));
}

@GetMapping("/{id}")
public ResponseEntity<ProductDto> getProduct(@PathVariable String id) {
    return productService.findById(id)
        .map(ResponseEntity::ok)
        .orElse(ResponseEntity.notFound().build());
}