Caused by: java.lang.ClassCastException: java.lang.Class cannot be cast to java.lang.reflect.ParameterizedType

new Unit().getBy(3L);

@MappedSuperclass
public abstract class Generic<T extends Generic> {
    @Transient
    public Class<T> entityClass;
    Generic() {
        entityClass = ((Class) ((Class) ((ParameterizedType) getClass().getGenericSuperclass()).getActualTypeArguments()[0]));
    }
    @Id
    @GeneratedValue(strategy = GenerationType.TABLE)
    public Long id;

    public T getBy(Long id) {
        return JPA.em().find(entityClass, id);
    }

@MappedSuperclass
public abstract class GenericDictionary<T extends Generic<T>> extends Generic<T> {

    @Required
    public String name;
    @Required
    public boolean active = true;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public boolean getActive() {
        return active;
    }

    public void setActive(boolean stat) {
        this.active = stat;
    }

@Entity
@Table(name="common__Unit")
public class Unit extends GenericDictionary<Unit> {
    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name="parent_id")
    public Unit parent;
}

new Unit().getBy(3L);

@Entity
@Table(name="common__Clinic")
public class Clinic extends GenericDictionary<Clinic> {
    @ManyToMany(cascade = CascadeType.PERSIST)
    public List<Unit> unit;

Clinic clinic = new Clinic().getBy(3L);