[英]OneToMany relation not load collection
I have a class Traveller
with a relationship with TravellerVote
. 我有一班
Traveller
与TravellerVote
有联系。 I wish retrieve the sending votes the travellers and the votes received. 我希望检索旅行者的发送票和收到的票。
Class Traveller 班级旅行者
@Entity
@PrimaryKeyJoinColumn(name="user_id")
public class Traveller extends User{
@OneToMany(mappedBy="voter", cascade={CascadeType.PERSIST, CascadeType.REMOVE})
protected List<TravellerVote> myVotes;
@OneToMany(mappedBy="partner", cascade={CascadeType.PERSIST, CascadeType.REMOVE})
protected List<TravellerVote> receivedVotes;
public Traveller(){
super();
myVotes = new ArrayList<TravellerVote>();
receivedVotes = new ArrayList<TravellerVote>();
}
public void addVote(TravellerVote vote){
myVotes.add(vote);
}
}
Class TravellerVote 旅行者舱票
@Entity
public class TravellerVote {
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(length=11)
protected long id;
@ManyToOne
@JoinColumn(name="voter_id")
protected Traveller voter;
@ManyToOne
@JoinColumn(name="partner_id")
protected Traveller partner;
@Column(nullable=false)
protected Date date;
@Column(length=300, nullable=true)
protected String comment;
@Column(nullable=false)
protected boolean positive;
public TravellerVote(Traveller voter, Traveller partner, String comment, boolean positive){
this.date = new Date();
this.voter = voter;
this.partner = partner;
this.comment = comment;
this.positive = positive;
}
}
The entities are persisted correctly in the database, with this: 可以使用以下方法将实体正确保留在数据库中:
TravellerDao dao = new TravellerDao();
Traveller t1 = dao.findByUsername("ramiromd");
Traveller t2 = dao.findByUsername("danimd");
Traveller t3 = dao.findByUsername("famartinezd");
t1.addVote(new TravellerVote(t1, t2, "Test comment", true));
t2.addVote(new TravellerVote(t2, t1, "Test comment", true));
t3.addVote(new TravellerVote(t3, t1, "Test comment", false));
dao.save(t1);
dao.save(t2);
dao.save(t3);
But, when in other controller try get the votes, the collections have 0 elements. 但是,当在其他控制器中尝试获得投票时,集合具有0个元素。
TravellerDao dao = new TravellerDao();
Traveller t1 = dao.findByUsername("ramiromd");
t1.getReceivedVotes().size(); // Must be 2 not 0.
t1.getMyVotes().size(); // Must be 1 not 0.
The TravellerDao save method: TravellerDao保存方法:
public void save(Traveller traveller) {
EntityManager em = PersistenceHelper.getEm();
em.getTransaction().begin();
em.persist(traveller);
//em.flush();
em.getTransaction().commit();
}
It is the findByUsername method: 这是findByUsername方法:
public Traveller findByUsername(String username){
EntityManager em = PersistenceHelper.getEm();
String qstring = "SELECT t FROM Traveller t WHERE t.username LIKE :username";
TypedQuery<Traveller> query = em.createQuery(qstring, Traveller.class);
query.setParameter("username", username);
return query.getSingleResult();
}
Any ideas ? 有任何想法吗 ?
In these scenarios , it is helpful to enable debugging for implementation framework. 在这些情况下,为实现框架启用调试是有帮助的。 For example , if you are using Hibernate , set the debug level of org.hibernate package to "DEBUG".
例如,如果您使用的是Hibernate,请将org.hibernate包的调试级别设置为“ DEBUG”。 That will show you all SQLs being fired.
这将向您显示所有被触发的SQL。 In your problem , if you set fetch equal to LAZY , you will see exact SQLs being fired for these statements :-
在您的问题中,如果将fetch设置为LAZY,则将看到针对这些语句触发的确切SQL:
t1.getReceivedVotes().size(); // Must be 2 not 0.
t1.getMyVotes().size();
Hopefully ,that will give you enough hint to solve this issue. 希望这会给您足够的提示来解决此问题。
I don't know how your dao save() method looks like but is there: 我不知道您的dao save()方法是什么样的,但是在那里:
getEntityManager().flush();
? ?
If no please add after persist and check whether it helped. 如果否,请在坚持后添加并检查是否有帮助。
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