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.

• Mast: Please do not update the code in your question to incorporate feedback from answers, doing so goes against the Question + Answer style of Code Review. This is not a forum where you should keep the most updated version in your question. Please see what you may and may not do after receiving answers .
• gtiwari333: FYI, you don't need to type @Autowired on constructor injection. Cheers just saved 2 line of code in each Component

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 :).

• Pitto: While that is correct this is a specific case where you can get an item by a property that I called id here but it was just to write an example. The key part of my question if how to handle the 404. Thanks for your contribution in any case!
• Pitto: Ps I have made my pseudocode more precise regarding your observation. xxxId is a specific property of my object, therefore the route I specified.
• Pitto: Still you have a very valid point, +1

Answer 2

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

.orElseThrow(ResourceNotFoundException::new);