I don't think it is possible with hibernate(-core) to map any collection of collections:
Collections may contain almost any
other Hibernate type, including all
basic types, custom types, components,
and of course, references to other
entities.
(from the official doc)
Notice the almost and the omission of the collection type.
A workaround: You need to introduce a new type 'in between' the collection holder and the element. This type you can map as an entity or a component and it refers the original content of the map, in this case a list.
Something like:
@Entity
public class Holder extends DomainObject {
@OneToMany
private Map<Enum,InBetween> inBetweens;
}
@Entity
public class InBetween extends DomainObject {
@OneToMany
private List<Element> elements;
}
@Entity
public class Element extends DomainObject {
private long valueId;
private int otherData;
}
@Mappedsuperclass
public class DomainObject {
// provides id
// optimistic locking
// create and update date
}
The rest of the mapping depends on your particular situation, but is rather straightforward.
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