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Java Spring Basics Using the MVC Architecture Add a CategoryController

Field injection is not recommended

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;

private final GifRepository gifRepository;

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

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";


2 Answers

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

Here's how to do constructor dependency injection:

public class GifController {
  private final GifRepository gifRepository;

  // Annotate your constructor with autowired
  public GifController(GifRepository gifRepository) {
    this.gifRepository = gifRepository;
Rodrigo Castro
Rodrigo Castro
15,652 Points

Hi Ricardo,

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

Hope it helps :)