How to return a "not found" feature in Spring?

Question

I’m running some tests on Spring to return error 404 in case he doesn’t find one id when searching in Repository, but is giving 200 OK.

@RequestMapping(value = "/{id}", method = RequestMethod.GET)
public ResponseEntity<?> buscar(@PathVariable("id") Long id) {
    Optional<Livro> livro = livrosRepository.findById(id);

    if(livro == null) {
        return ResponseEntity.notFound().build();
    }

    return ResponseEntity.status(HttpStatus.OK).body(livro);
}`

Does anyone know what might be going on?

Answer 1

I see two ways to do what you want:

1 - Same as @Tom Melo commented

@RequestMapping(value = "/{id}", method = RequestMethod.GET)
public ResponseEntity<?> buscar(@PathVariable("id") Long id) {
    Optional<Livro> livro = livrosRepository.findById(id);

    if(!livro.isPresent()) { // Mudança aqui
        return ResponseEntity.notFound().build();
    }

    return ResponseEntity.status(HttpStatus.OK).body(livro);
}

This way you use the Optional isPresent method

2 - Or otherwise

@RequestMapping(value = "/{id}", method = RequestMethod.GET)
public ResponseEntity<?> buscar(@PathVariable("id") Long id) {
    Livro livro = livrosRepository.findById(id).orElse(null);//Mudança aqui

    if(livro == null) {
        return ResponseEntity.notFound().build();
    }

    return ResponseEntity.status(HttpStatus.OK).body(livro);
}

This way you hope to return a Book and if you do not find it will be null, by your line of thought this seems more appropriate but the two methods will do the same thing in the end

Answer 2

Your code can become more declarative using the methods of Optional, without the need for a if:

@RequestMapping(value = "/{id}", method = RequestMethod.GET)
public ResponseEntity<?> buscar(@PathVariable("id") Long id){
    return livrosRepository.findById(id)
      .map(ResponseEntity::ok)
      .orElseGet(() -> ResponseEntity.notFound().build());
}