的实例而解决
我正在尝试使用JPA编辑和实体,但我没有做任何事情,为什么?
public void editExam(Exam e) {
Exam ex=getExam(e.getIdExam());
EntityManagerFactory emf = Persistence.createEntityManagerFactory("QuizPU");
EntityManager em = emf.createEntityManager();
em.getTransaction().begin();
ex.setQuestions(e.getQuestions());
em.getTransaction().commit();
em.close();
emf.close();
}
我正在尝试更改列表的questions
的值。这就是在我的Exam
实体类中编码的方式
@OneToMany (cascade = ALL)
@JoinTable(name="jnt_Exam_Question",
joinColumns = @JoinColumn(name="idExam"),
inverseJoinColumns = @JoinColumn(name="idQuestion"))
private List<Question> questions;
我的getexam((方法
public Exam getExam(Long idExam) {
EntityManagerFactory emf = Persistence.createEntityManagerFactory("QuizPU");
EntityManager em = emf.createEntityManager();
String req1 ="select e from Exam e where e.idExam = ?1";
Query q1 = em.createQuery(req1);
q1.setParameter(1, idExam);
Exam e =(Exam) q1.getSingleResult();
em.close();
emf.close();
return e;
}
仅通过创建一个EntityManagerFactory