@ManyToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @JoinTable(
            name = "SEC_USER_ROLE",
            joinColumns = {
                @JoinColumn(name = "SEC_USER_ID", referencedColumnName = "SEC_USERS")},
            inverseJoinColumns = {
                @JoinColumn(name = "SEC_ROLE_ID", referencedColumnName = "SEC_ROLES")})
    private List<Role> roles;  

@ManyToMany(mappedBy = "roles", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
private List<User> users;

@Override
@Transactional(readOnly = false, propagation = Propagation.REQUIRED)
public T merge(T o) {

    o = em.merge(o);
    em.flush();
    return o;
}