spring mysql事务语句

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

@Service
public class UserService {

    @Autowired
    private UserRepository userRepository;

    @Transactional
    public void transfer(int fromId, int toId, double amount) {
        // 扣款操作
        User fromUser = userRepository.findById(fromId).orElseThrow(() -> new RuntimeException("User not found"));
        fromUser.setBalance(fromUser.getBalance() - amount);
        userRepository.save(fromUser);

        // 充值操作
        User toUser = userRepository.findById(toId).orElseThrow(() -> new RuntimeException("User not found"));
        toUser.setBalance(toUser.getBalance() + amount);
        userRepository.save(toUser);
    }
}