Hibernate, ElementCollection, and Transactions http://www.adamweigold.com/2011/11/hibernate-elementcollection-and.html Hibernate implemented @ElementCollection in the JPA by binding the persistence of the ElementCollection of a new entity at the end of the transaction, and NOT at the time you tell the EntityManager to persist. Under most use cas…

ParentEntity.java

@Entity
@Table(name = "ParentEntity")
public class ParentEntity {

    @Id
    @GeneratedValue
    @Column(name= "ParentId")
    private long parentId;

    @ElementCollection(fetch = FetchType.EAGER)
    @CollectionTable(name = "ChildrenNames", joinColumns = @JoinColumn(name = "ParentId"))
    @Column(name = "ChildName")
    private Set<String> children;

    public Set<String> getChildren() {
        return children;
    }

    public void setChildren(Set<String> children) {
        this.children = children;
    }

    @Column(name = "ParentName")
    private String parentName;

    public String getParentName() {
        return parentName;
    }

    public void setParentName(String parentName) {
        this.parentName = parentName;
    }
}

ParentRepository.java

@Repository
public class ParentRepository {

    @PersistenceContext

    EntityManager entityManager;

    public void saveParent(ParentEntity parentEntity){
        entityManager.persist(parentEntity);
    }

    public void detachParent(ParentEntity parentEntity){
        entityManager.detach(parentEntity);
    }

    public ParentEntity getParentByName(String parentName){
        TypedQuery<ParentEntity> query = entityManager.createQuery("SELECT p FROM ParentEntity p WHERE p.parentName = :parentName", ParentEntity.class);
        query.setParameter("parentName", parentName);
        return query.getSingleResult();
    }
}

ParentServiceImpl.java

@Service
public class ParentServiceImpl implements ParentService {

    @Autowired
    ParentRepository parentRepository;

    @Transactional
    public void saveParent(ParentEntity parentEntity){
        parentRepository.saveParent(parentEntity);
        parentRepository.detach(parentEntity);
    }
}