LazyInitializationException when saving one side of a relationship

Question

I have a class Patient that has a collection of Id, and a collection of Folders. When I try to save a Folder on its own it throws a LazyInitializationException because of the Patient's id collection.

Patient class looks like this:

@Entity
@Table(name = "patient")
public class Patient implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private Long id;

    @OneToMany(mappedBy = "patient", fetch = FetchType.LAZY, orphanRemoval = true, cascade = CascadeType.ALL)
    private Set<Id> ids = new HashSet<Id>();

    @OneToMany(mappedBy = "patient", fetch = FetchType.LAZY, orphanRemoval = true, cascade = CascadeType.ALL)
    private List<Folder> folders = new ArrayList<Folder>();

    ...
}

Folder class looks like this:

@Entity
@Table(name = "folder")
public class Folder implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private Long id;

    @ManyToOne
    @JoinColumn(name = "patient_id", referencedColumnName = "id")
    private Patient patient;

}

Then I have a service class that does things and then saves a folder like this:

@Override
@Transactional
public void importData(Data data) {

    // do other things
    Folder folder = new Folder();
    // initialize folder values
    ...
    folder.setPatient(patient);
    folderDAO.save(folder);
    ...
}

And when it tries to save the folder in FolderDAO with:

getHibernateTemplate().saveOrUpdate(folder);

It throws:

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: es.mycompany.myapp.Patient.ids, could not initialize proxy - no Session
    at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:587)

Answer 1

The issue is that you're trying to saveOrUpdate outside of the session. Hibernate.initialize will initialize your Patient collection for use prior to your saveOrUpdate, or you can manually open a hibernate session, transaction, do commit and close the resources.

Try like this: https://www.mkyong.com/hibernate/hibernate-transaction-handle-example/

Answer 2

with a cascade = ALL configuration, you are configuring hibernate to update the list/set of patient when the folder entity is saved, the patient list must be loaded in memory to be updated. You may be able to try to remove CASCADE = ALL and manually manage any list and set of patient class updates.