How can I fetch multiple lazy loaded OneToMany lists? - jpa

Question

I have an Entity with multiple unidirectional OneToMany relationships like following.
How can I fetch all this fields in one query?
What would be the best way if I have up to 10 Arraylists with a OneToMany relationship?
#Data
#EqualsAndHashCode(callSuper = true)
#Entity
#Table(name = "members")
public class Member extends Auditable<String> {
#Id
#GeneratedValue(strategy = GenerationType.SEQUENCE)
#Setter(AccessLevel.NONE)
private Long id;
#OneToOne
private Gender gender;
private String lastName;
private String firstName;
#OneToMany(cascade = CascadeType.ALL, orphanRemoval = true, fetch = FetchType.LAZY)
#JoinColumn(name = "person_id")
private List<Phone> phoneList = new ArrayList<>();
#OneToMany(cascade = CascadeType.ALL, orphanRemoval = true, fetch = FetchType.LAZY)
#JoinColumn(name = "person_id")
private List<EMail> eMailList = new ArrayList<>();
// more Lists with OneToMany relationship
}
#Data
#EqualsAndHashCode(callSuper = true)
#Entity
#Table(name = "emails")
public class EMail extends Auditable<String> {
#Id
#GeneratedValue(strategy = GenerationType.SEQUENCE)
#Setter(AccessLevel.NONE)
private Long id;
private Type type;
private String value;
}
I tried following step in my MemberRepository class which is ending in a MultipleBagFetchException:
#Query("SELECT m " +
"FROM Member m " +
"LEFT JOIN FETCH m.eMailList " +
"LEFT JOIN FETCH m.phoneList " +
"WHERE m.memberId = ?1")
Optional<Member> findByMemberIdWithAllInfoQuery(Long id); // MultipleBagFetchException
Then I tried following step with this information https://vladmihalcea.com/hibernate-multiplebagfetchexception/ which also doesn't work properly:
public Optional<Member> findMemberWithAllFieldsQuery(Long memberId) {
Member _member = entityManager.createQuery(
"SELECT DISTINCT m " +
"FROM Member m " +
"LEFT JOIN FETCH m.eMailList " +
"WHERE m.memberId = :id ", Member.class)
.setParameter("id", memberId)
.setHint(QueryHints.HINT_PASS_DISTINCT_THROUGH, false)
.getSingleResult();
_member = entityManager.createQuery(
"SELECT DISTINCT m " +
"FROM Member m " +
"LEFT JOIN FETCH m.phoneList " +
"WHERE m in :member ", Member.class)
.setParameter("member", _member)
.setHint(QueryHints.HINT_PASS_DISTINCT_THROUGH, false)
.getSingleResult();
return Optional.of(_member);
}
Thanks for your help/hints!

Answer 1

Try to use Set instead of List ? I've run into this exception and solved it after changing my collection to Set
#OneToMany(cascade = CascadeType.ALL, orphanRemoval = true, fetch = FetchType.LAZY)
#JoinColumn(name = "person_id")
private Set<Phone> phoneList = new HashSet<>();
#OneToMany(cascade = CascadeType.ALL, orphanRemoval = true, fetch = FetchType.LAZY)
#JoinColumn(name = "person_id")
private Set<EMail> eMailList = new HashSet<>();