Fast Object Database for Java - with JPA/JDO support

How to delete M2M relationship?


In user model class I have the following:

public class User implements Serializable {
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @ManyToMany(mappedBy = "attendees", cascade = CascadeType.ALL)
    private Set timeslots = new HashSet();

And i would like to delete the timeslots..i've tried something but doesnt work, as follows:

public static boolean deleteUserTimeslot(EntityManager em, Timeslot ts) {

    EntityTransaction transaction = em.getTransaction();
    try {
        ArrayList<User> attendeeList = (ArrayList<User>) ts.getAttendees();

        List<User> attendeesToRemove = (List<User>) getAllUsers(em);

        for(User u: attendeesToRemove){
            for(int i=0;i<attendeeList.size();i++){


        return true;
    } catch (PersistenceException ex) {
        //Rolling back data transactions
        if (transaction != null && transaction.isActive()) {
        logger.error("Error making database call for update timeslot status");
    } catch (Exception e) {
        logger.error(e.getMessage(), e);
    return false;

Every entity object has to be removed by a separate invocation of the remove method. Removing a set of time slots in one invocation (as in your code) is not supported by JPA.

If Timeslot is the owner of the many-to-many relationship then the other side will be updated automatically when User instances are loaded again from the database (you can use clear or refresh to enforce update).

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ObjectDB - Fast Object Database for Java (JPA/JDO)

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