Return a 404 when a resource is not found in Spring Boot

Question

I wrote this code in order to return a http status of not found to my users in case the resource is not present in the DB.

@RestController
public class ExampleController {

    public final ExampleService exampleService;

    @Autowired
    public ExampleController(ExampleService exampleService) {
        this.exampleService = exampleService;
    }

    @ResponseStatus(value = HttpStatus.NOT_FOUND)
    public class ResourceNotFoundException extends RuntimeException {
    }

    @GetMapping("/api/mappings/get-by-id/{id}")
    public ExampleDto getExampleById(@PathVariable String id) {
        Example example = exampleService.findById(id).orElse(null   );
        if (example == null) throw new ResourceNotFoundException();
        return new ExampleDto(example);
    }

}

I would like to know if this code can be considered good and robust enough or if it can be improved and how.

Answer 1

Your URL path isn't very RESTlike. You have built the URL to describe an operation when a more common approach is to build the URL to describe a resource.

So instead of https://example.com/api/mappings/get-by-id/42 one would build a URL like https://example.com/api/mappings/42.

The name get-by-id is fully redundant in REST world as the "get" operation is already defined in the HTTP GET-method (the @GetMapping annotation in Spring Boot) and identifying resources by their identifier is always the default operation :).

Answer 2

As often happens after sleeping on it I had a better solution:

.orElseThrow(ResourceNotFoundException::new);