Question

 private Set<Employee> assignees = new HashSet<>();  



 public Set<Employee> getAssignees() {
            return assignees;
        }

        public void setAssignees(Set<Employee> assignees) {
            this.assignees = assignees;
        }

我在下面的代码中使用了上面的方法，当运行该代码时，我得到了这个异常。

 `Resolved exception caused by Handler execution: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role:`

它来自执行 agendaInfo.setAssignees(item.getAssignees());行。为什么会得到这个例外？

@Override
        public List<AgendaContentDTO> getAgendasByMeetingId(Long meetingId) {

            List<Agenda_content> agendas = extendedAgendaContentRepository.getAgendasByMeetingId(meetingId);
            List<AgendaContentDTO> agendaDTOS = new ArrayList<>();

            Long currentUser = utils.getCurrentEmployeeId();

            for (Agenda_content item: agendas){

                AgendaContentDTO agendaInfo = new AgendaContentDTO();

                agendaInfo.setId(item.getId());
                agendaInfo.setTitle(item.getTitle());
                agendaInfo.setContent(item.getContent());
                agendaInfo.setMeetingId(item.getMeeting().getId());
                agendaInfo.setMeetingMeetingName(item.getMeeting().getMeetingName());
                agendaInfo.setAssignees(item.getAssignees());

              agendaDTOS.add(agendaInfo);
            }
            return agendaDTOS;
        }

public interface ExtendedAgendaContentRepository extends Agenda_contentRepository {

    @Query("select distinct e.meeting from Agenda_content e join e.assignees a where a.id =:assigneeId")
    public List<Meeting> getMeetingsAssignedToMe(@Param("assigneeId") long assigneeId);

    @Query("select distinct e from Agenda_content e where e.meeting.id =:meetingId")
    public List<Agenda_content> getAgendasByMeetingId(@Param("meetingId") long meetingId);


}

Answer 1

集合在hibernate中是延迟加载的，所以当你从getAgendasByMeetingId加载你的数据时，hibernate加载了Agenda_content列表，但没有加载集合（Assignees）。

LazyInitializationException是geeting，因为没有事务处理（No Session open）可用 SELECT TOP 1 Waiter, sum(tips)Tips FROM T GROUP BY waiter ORDER BY sum(tips) DESC代码

如果您使用的是spring，请使用@Transaction标记您的方法或者在休眠状态下，你需要打开一个会话

或者您可以在集合中使用fetchType = FetchType.EAGER，因此hibernate会在加载Agenda_content期间加载所有getAssignees。

尝试分配HashSet时会出现LazyInitializationException

1 个答案: