@Entity(name = "DataPlanFamily")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(discriminatorType = DiscriminatorType.STRING, name = "TYPE_DISCRIMINATOR", length = 50)
@Table(name = "DATA_PLAN_FAMILY")
public abstract class DataPlanFamily implements IDataPlanFamily {
    ...
    @OneToMany(cascade = {CascadeType.PERSIST, CascadeType.MERGE}, mappedBy = "family", fetch = FetchType.EAGER)
    @JoinColumn(name="FAMILY_ID")
    private Set<DataPlan> plans = new HashSet<DataPlan>();

    public Set<DataPlan> getPlans() {
        return plans;
    }

    public void setPlans(Set<DataPlan> plans) {
        this.plans = plans;
    }

    public void addPlan(DataPlan plan) {
        // THERE CAN BE ONLY ONE!!!
        if (!getPlans().contains(plan)) {

            // Add the plan to this family's list of plans.
            getPlans().add(plan);

            // If this plan is already associated with another family, remove this plan from that
            // family before adding it to this family.  Note: this behavior of changing the family
            // with which a plan is associated may not be provided at a higher level, but just in case.
            if (plan.getFamily() != null) {
                plan.getFamily().getPlans().remove(plan);
            }

            // Set the plan's family to this.
            plan.setFamily(this);
        }
    }
    ...
}


@Entity(name = "DataPlan")
@Inheritance(strategy = InheritanceType.JOINED)
//@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(discriminatorType = DiscriminatorType.STRING, name = "TYPE_DISCRIMINATOR", length = 50)
@Table(name = "DATA_PLAN")
public abstract class DataPlan implements IDataPlan {
    ...
    @ManyToOne
    @JoinColumn(name="FAMILY_ID", nullable = false)
    @ForeignKey(name="FK_FAMILY_ID")
    private DataPlanFamily family;

    public DataPlanFamily getFamily() {
        return family;
    }

    public void setFamily(DataPlanFamily family) {
        this.family = family;
    }

    ...
}


@Entity(name = "AssessmentPlanFamily")
@DiscriminatorValue("AssessmentPlanFamily")
public class AssessmentPlanFamily extends DataPlanFamily implements IAssessmentPlanFamily {

}


@Entity(name = "AssessmentPlan")
@Inheritance(strategy = InheritanceType.JOINED)
@Table(name = "ASSESSMENT_PLAN")
@DiscriminatorValue("AssessmentPlan")
public class AssessmentPlan extends DataPlan implements IAssessmentPlan {
    ...
}

apfMaintenanceForm.getAssessmentPlanFamily().addPlan((DataPlan)apMaintenanceForm.getAssessmentPlan());

javax.ejb.EJBException: See nested exception; nested exception is: javax.persistence.PersistenceException: org.hibernate.InstantiationException: Cannot instantiate abstract class or interface: com.churchmutual.ocns.dataplan.model.jpa.DataPlanFamily