How to map an abstract collection with jpa?

I am trying to work out if it is possible get JPA to persist an abstract collection with concrete implementations.

So far my code looks like this:

@Entity
public class Report extends Model {

    @OneToMany(mappedBy = "report",fetch=FetchType.EAGER)
    public Set<Item> items;
}

@MappedSuperclass
public abstract class OpsItem extends Model {

    @ManyToOne
    public RetailOpsBranch report;
}


@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class AItem extends OpsItem {
...
}

@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class BItem extends OpsItem {
...
}

But I keep stumbling on the mapping error below and I don't really know if this is feasible?

JPA error
A JPA error occurred (Unable to build EntityManagerFactory): Use of @OneToMany or
@ManyToMany targeting an unmapped class: models.Report.items[models.OpsItem]

UPDATE

I don't think the problem is with the abstract class but the the @MappedSuperClass annotation. It looks like jpa does not like to map the one to many relationship with a @MappedSuperClass. If I change the abstract class into a concrete class I have the same error.

If I then change to @Entity annotation this seem to work with both the abstract and concrete class.

This seems a bit strange to map an abstract class with @Entity. I'm I missing anything?

SOLUTION

Managed to figure it out with the help from rhinds. Two points to note:

1) the abstract class needs to be annotated with @Entity and inheritance strategy of table per class for the subclasses to have their own table.

2) Identity Id generation will not work in this scenario and I had to use Table generation type.

@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public abstra