如何初始化網絡服務

Question

我正在嘗試創建一個簡單的網頁，該網頁顯示從Web服務接收的數據

@Service
@Transactional
public class TopicService {
    @Autowired
    private TopicRepository topicRepository;

    public int saveTopic(Topic topic){
        return topicRepository.save(topic).getId();

        }

    public Iterable<Topic> findAllTopics(){
        return topicRepository.findAll();

    }

    public Topic findTopicByID(Long id){
        return topicRepository.findOne(id);
    }

    public List<Topic> findTopicsByTag(Tag tag){
        return topicRepository.findAllByTopicTag(tag);
    }

}

主題存儲庫擴展了CRUD存儲庫

@Repository
public interface TopicRepository extends CrudRepository<Topic, Long>
{
    List<Topic> findAllByTopicTag(Tag currentTag);

} 

控制器通過以下方式調用服務

@Controller
public class HomeController {

    private TopicService service;

    private static final Logger logger = LoggerFactory.getLogger(HomeController.class);

    @RequestMapping(value = "/", method = RequestMethod.GET)
    public ModelAndView home(Locale locale, Model model) 
    {
         Iterable<Topic> listTopic = service.findAllTopics();
         return new ModelAndView("home", "model", listTopic);
}
}

這個字符串

可迭代的listTopic = service.findAllTopics（）;

拋出空指針異常。 我猜是因為服務沒有初始化。 如何執行服務的正確初始化？

Answer 1

您需要在HomeController自動連接TopicService ：

@Controller
public class HomeController {

    @Aurowired
    private TopicService service;