Spring Autowired service is null

Question

I have RestController class that calls Presenter to get some data.

@RestController
@RequestMapping(value="notes/api")
public class NotesRestController {

private GetAllNotesPresenter getAllNotesPresenter;

@RequestMapping(value="/all")
public List<Note> getAll(){
    getAllNotesPresenter = new GetAllNotesPresenterImpl();
    return getAllNotesPresenter.getAll();
}

}

Inside Presenter class I call DataSource (not Spring Repository, just DAO class).

public class GetAllNotesPresenterImpl implements GetAllNotesPresenter {

private NotesDataSource dataSource;
private NotesRepository repository;

public GetAllNotesPresenterImpl(){

    dataSource = new DatabaseDataSource();
    repository = new NotesRepositoryImpl(dataSource);
}
@Override
public List<Note> getAll() {
    return repository.getAll();
}

}

This is my Repository class, it is not Spring Repository, it just DAO class.

public class NotesRepositoryImpl implements NotesRepository {

private NotesDataSource dataSource;

public NotesRepositoryImpl(NotesDataSource dataSource){
    this.dataSource = dataSource;
}

@Override
public List<Note> getAll() {
    return dataSource.getAll();
}

}

This is my Service class:

@Service
@Transactional
public class NotesServiceImpl implements NotesService {

@Autowired
private NotesJpaRepository repository;

@Override
public List<NoteJpa> getAll() {
    return repository.findAll();
}

}

Inside DataSource class I want to do @Autowire of Spring service, but I get null pointer exception. Service is always null.

@Component
public class DatabaseDataSource implements NotesDataSource {

@Autowired
private NotesService notesService;

public DatabaseDataSource(){
}

@Override
public List<Note> getAll() {
    return notesService.getAll();
}

}

Solution

Even though you have annotated the DatabaseDataSource as @Component, you are not injecting, and thus using it as Spring Bean along the way. You simply create it by hand:

public GetAllNotesPresenterImpl(){

    dataSource = new DatabaseDataSource();
    repository = new NotesRepositoryImpl(dataSource);
}

In order to take advantage of injection of this bean:

@Autowired
private NotesService notesService;

you would need to use Spring injection starting from the top (this is only one of the ways you can go about it):

1) Inject the dataSource in the controller:

@RestController
@RequestMapping(value="notes/api")
public class NotesRestController {

private GetAllNotesPresenter getAllNotesPresenter;

@Autowired
private NotesDataSource dataSource;

@RequestMapping(value="/all")
public List<Note> getAll(){
    getAllNotesPresenter = new GetAllNotesPresenterImpl(dataSource);
    return getAllNotesPresenter.getAll();
}

2) Change the constructor of the GetAllNotesPresenterImpl:

public GetAllNotesPresenterImpl(NotesDataSource dataSource){

    this.dataSource = dataSource;
    repository = new NotesRepositoryImpl(dataSource);
}

Other option would be to make GetAllNotesPresenterImpl and NotesRepositoryImpl as spring beans and inject dataSource in the NotesRepositoryImpl directly. The final call is up to you.