“Illegal attempt to map a non collection as a @OneToMany, @ManyToMany or @CollectionOfElements”

Question

Good morning Stackoverflow,

I have the problem that it gives me the error:

Failed to create sessionFactory object.org.hibernate.AnnotationExcept

Answer 1

You should map to interfaces and not implementations. This:

@OneToMany(cascade=CascadeType.ALL, targetEntity=CoachGroup.class)
@JoinColumn(name="id")
private TreeSet coachGroups = new TreeSet<>();

Should be (also replaced the TreeSet because a HashSet is enough here):

@OneToMany(cascade=CascadeType.ALL, targetEntity=CoachGroup.class)
@JoinColumn(name="id")
private Set coachGroups = new HashSet<>();