UserService NullPointerException Spring / Hibernate

Question

我有一个使用Spring / Hibernate的maven项目，并且我在this.userService.save(user);处继续获得NullPointerException。 UserService是@Autowired，所以我不确定为什么会抛出NPE。 使用UserService的代码示例：

@Component
public class BotService extends TelegramLongPollingBot {

    @Autowired
    private UserService userService;

    @Autowired
    private MessagesService messagesService;

    @Override
    public void onUpdateReceived(Update update) {
        Message message = update.getMessage();
        String text = message.getText();
        User user = new User();
        user.setTelegramId(message.getFrom().getId());
        user.setFirstName(message.getFrom().getFirstName());
        user.setLastName(message.getFrom().getLastName());
        Messages messages = new Messages();
        messages.setUser(user);
        messages.setId(user.getId());
        messages.setText(text);
        this.userService.save(user); // <-- NPE 
        }
    }

UserRepository.java

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

import com.example.model.User;

@Repository
public interface UserRepository extends JpaRepository<User, Long>{
    User findById(int id);
}

UserService.java

import com.example.model.User;

public interface UserService {
    public User findById(int id);
    public void save(User user);
}

UserServiceImpl.java

import javax.transaction.Transactional;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import com.example.model.User;
import com.example.repository.UserRepository;

@Service("userService")
public class UserServiceImpl implements UserService{

    @Autowired
    private UserRepository userRepository;

    @Override
    @Transactional
    public void save(User user) {
        userRepository.save(user);
    }

    @Override
    public User findById(int id) {
        return userRepository.findById(id);
    }
}

UPD。添加了详细说明

BotExampleApplication.java：

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.transaction.annotation.EnableTransactionManagement;
import org.telegram.telegrambots.ApiContextInitializer;
import org.telegram.telegrambots.TelegramBotsApi;
import org.telegram.telegrambots.exceptions.TelegramApiException;
import org.telegram.telegrambots.starter.EnableTelegramBots;

import com.example.service.BotService;

@SpringBootApplication
@EnableTelegramBots
@EnableTransactionManagement
public class BotExampleApplication {

    public static void main(String[] args) {
        ApiContextInitializer.init();

        TelegramBotsApi botsApi = new TelegramBotsApi();

        try {
            botsApi.registerBot(new BotService());
        } catch (TelegramApiException e) {
            e.printStackTrace();
        }
        SpringApplication.run(BotExampleApplication.class, args);
    }
}

堆栈跟踪：

java.lang.NullPointerException: null
    at com.example.service.BotService.onUpdateReceived(BotService.java:46) ~[classes/:na]
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1380) ~[na:na]
    at org.telegram.telegrambots.generics.LongPollingBot.onUpdatesReceived(LongPollingBot.java:27) ~[telegrambots-meta-3.6.1.jar:na]
    at org.telegram.telegrambots.updatesreceivers.DefaultBotSession$HandlerThread.run(DefaultBotSession.java:309) ~[telegrambots-3.6.1.jar:na]

有什么建议吗？

Answer 1

您永远不应该创建弹簧组件的新实例。在您的主要课程new中使用BotService创建。这与spring创建的@Autowired实例不同。 BotService仅适用于spring组件，并且因为您使用的是另一个实例，所以依赖项永远不会注入其中。

要使其工作，请从spring上下文中获取ConfigurableApplicationContext context = SpringApplication.run(...); BotService service = context.getBean(BotService.class); 实例，然后使用它进行注册。

{{1}}

Answer 2

你应该添加setter和getter @Autowired private UserRepository userRepository; /* setter and getter forr user userRepository*/

等在另一个文件中

@Autowired
private UserService userService;

@Autowired
private MessagesService messagesService;
/*setters and getters here too */