java EM不会持久化到数据库中

Question

我正在使用SpringBoot并尝试将新对象持久化到db，但什么也没发生。对于另一个实体，我得到了相同的方法，它是有效的。有什么建议吗

实体：

@Entity
@Table(name = "subject")
public class Subject implements Serializable{

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;

@Column(name = "name")
private String name;

@OneToMany(mappedBy = "subject")
private Set<Question> questions =new HashSet<>();

DAO:

import org.springframework.transaction.annotation.Transactional;
@Autowired
private EntityManager entityManager;
@Repository
@Transactional
public class QuestionDaoImpl implements QuestionDao {
public void createNewSubjectByName(String name) {
    Subject subject = new Subject();
    subject.setName(name);
    entityManager.persist(subject);
}

Answer 1

@Transactional
public Subject createNewSubjectByName(String name) {
    EntityManager entityManager = entityManagerFactory.createEntityManager();
    Subject subject = new Subject();
    subject.setName(name);
    entityManager.getTransaction().begin();
    entityManager.persist(subject);
    entityManager.flush();
    entityManager.getTransaction().commit();
    entityManager.close();
    return subject;
}