java Hibernate实体向实体添加业务逻辑？

Question

我有：

@Entity(name = "Term")
@Table(name = "extra_term")
public class Term implements Cloneable, Serializable{

此实体具有ID

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private Long id;

并且该实体具有该实体拥有的用户列表属性（用户已注册到term）

@OneToMany(cascade = CascadeType.ALL)
@JoinTable(name = "etc. etc. etc. })    
private List<TermUser> users = new ArrayList<TermUser>();   

是否可以声明业务方法来计算注册到具体术语的用户总数？差不多

public long getUsersCount() {
  return QUERY TO THE DATABASE "GET COUNT OF USERS REGISTERED TO TERM WITH ID
  (where ID is the id of this entity?)"
}

我需要直接从entitz计算注册到term的用户数，但我不想在DB中有一个属性“registeredUsersCount”