“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 are not allowed to use a concrete implementation on the entities field declaration. You are allowed to use one of the following:

• java.util.List
• java.util.Set
• java.util.Collection

So in your case it would have to be:

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