Question

Is it possible to get as a result from hibernate directly this…

List<Map<Sth, List<SthLog> list;

when classes are mapped in such a way (not bidirectional)?:

@Entity
public class SthLog {

        @ManyToOne(fetch=FetchType.LAZY, cascade=CascadeType.ALL)
    private Sth sth; }

I know that this maybe seems to be a silly question, because normally you can add bidirectional mapping, but in this case I can change entities definition and I wonder if I can get required structure directly from hibernate.

Answer 1

Just don’t expect Hibernate to do everything for you. Transforming a List into a Map (or a Guava Multimap, which is easier and more appropriate here) is a matter of 3 lines of codes:

// get all the SthLog with their sth
List<SthLog> list = 
    session.createQuery("select s from SthLog s inner join fetch s.sth").list();
// index them by their sth
ListMultimap<Sth, SthLog> result = ArrayListMultimap.create();
for (SthLog sthLog : list) {
    result.put(sthLog.getSth(), sthLog);
}