Field injection is not recommended

Question

This what IDEA says about the @Autowired, and I can't compile it... Can you please take a look? Thks!

@Autowired private final CategoryRepository categoriesRepository;

@Autowired
private final GifRepository gifRepository;


@RequestMapping("/categories")
public String listCategories(ModelMap modelmap) {
    List<Category> allCategories = categoriesRepository.getAllCategories();
    modelmap.put("categories", allCategories);
    return "categories";
}

@RequestMapping("/category/{id}")
public String category(@PathVariable int id, ModelMap modelMap) {
    Category category = categoriesRepository.findById(id);
    modelMap.put("category", category);
    List<Gif> gifs = gifRepository.findByCateogoryId(id);
    modelMap.put("gifs", gifs);
    return "category";
}

}

Answer 1 · 2017-09-04T13:47:31Z

September 4, 2017 1:47pm

Field dependency injection could result in a NullPointerException, so it's not considered a best practice.

Here's how to do constructor dependency injection:

@Controller
public class GifController {
  private final GifRepository gifRepository;

  // Annotate your constructor with autowired
  @Autowired
  public GifController(GifRepository gifRepository) {
    this.gifRepository = gifRepository;
  }
}

Answer 2 · 2018-04-13T14:06:10Z

April 13, 2018 2:06pm

Hi Ricardo,

The GifRepository field is declared as 'final', so the compiler would expect it to be initialised. Try removing the ‘final’ word to see if it compiles.

Hope it helps :)

Welcome to the Treehouse Community

Looking to learn something new?

Ricardo Sala

Ricardo Sala

Field injection is not recommended

2 Answers

Adam Fields

Adam Fields

Rodrigo Castro

Rodrigo Castro