@Entity
public class Employee {
   @Id @GeneratedValue public long ind;
   @ManyToMany Set<Manager> managers = new HashSet<>();
   @ManyToMany Set<Employee> friends = new HashSet<>();
}

@Entity
@NamedEntityGraph(
   name="managerfriends",
   includeAllAttributes=false,
   attributeNodes = {
       @NamedAttributeNode(value='friends')
  }
)
public class Manager extends Employee { }