I solved this by changing List<> to Set<> on the ManyToMany and OneToMany relations
No Session found for current thread
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17-07-2023 - |
Domanda
I am trying to get the size of attendees (a list, which is a oneToMany in class Presentation)
Planning contains a OneToMany with the corresponding presentations
Every time i try to get the size of attendees it fails to lazy load them. I tried writing a query but it says that i can't use the fetch twice. Is there any good way to get the data i need?
There are a lot of discussions on the internet about this but none of them seem to solve my problem.
I am running on the latest version of hibernate (4.1.7.Final) and am using spring Release 3.2.3
Planning repo:
public interface PlanningRepository extends JpaRepository<Planning, Long>{
@Query("select pl from Planning pl join fetch pl.presentations p join fetch p.attendees a where pl.id = ?1")
Planning findOneById(Long id);
}
The relation in class Presentation:
@ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
@JoinTable(name = "presentation_attendees",
joinColumns = {@JoinColumn(name = "presentation_id")},
inverseJoinColumns = {@JoinColumn(name = "student_id")})
private List<Student> attendees;
The relation in student:
@ManyToMany(mappedBy = "attendees")
private List<Presentation> presentationsAttending;
Where i call it in PlanningController:
Planning planning = planningRepository.findOneById(1L);
JSONArray pArray = new JSONArray();
JSONObject planningJSON = new JSONObject();
//List<Presentation> presentations = (List<Presentation>)presentationRepository.findByPlanning(planning.getId());
for(Presentation p : planning.getPresentations())
{
sessionFactory.openSession();
sessionFactory.getCurrentSession().getTransaction().begin();
//i need the size of attendees
presentationJSON.put("subscribers", p.getAttendees().size());
sessionFactory.getCurrentSession().getTransaction().commit();
sessionFactory.close();
}
dispatcher-servlet.xml:
<bean id="sessionFactory"
class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
<property name="dataSource" ref="dataSource" />
</bean>
<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="persistenceUnitName" value="school"/>
<property name="dataSource" ref="dataSource" />
</bean>
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>
<bean id="txManager" class="org.springframework.orm.hibernate4.HibernateTransactionManager">
<property name="sessionFactory" ref="sessionFactory" />
</bean>
<bean id="persistenceExceptionTranslationPostProcessor" class="org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor"/>
Soluzione 2
Altri suggerimenti
You need to enclose your Repository calls inside of a Service method.
Ex:-
PresentationService
@Transactional
public List<Long> getAttendeesCountForPlanning(Long planningId) {
...
}
This must return the List of Presentation Attendees Count for each Planning Id. So this will be enclosed within a single transaction. For more information read this post
Strange as it seems calling a transactional method in the method does not work. For example, see
@Service
public class MyServiceImpl implements MyService{
@Autowired
MyDAO myDAO;
@Override
@Transactional(readOnly=true)
public MyObject method1(String param) {
return MyObject myObject = myDAO.get(param);
}
@Override
//Won't work without the transactional annotation
public MyObject method2() {
return method1("bla");
}
}