JPA合并只读字段

@Entity
public class Person
{
   @Id
   private String email;

   @OneToOne(fetch = FetchType.LAZY)
   @JoinColumn(insertable = false,updatable = false)
   private ReadOnly readOnly;

   @Column
   private String name;      

   @XmlElement
   public String getEmail()
   {
      return email;
   }

   public void setEmail(String email)
   {
      this.email = email;
   }

   @XmlElement
   public Long getReadOnlyValue()
   {
      return readOnly.getValue();
   }

   // more get and set methods
}

这是场景.
客户端创建Web服务请求以创建人员.在服务器端,一切都很简单.
它确实按预期工作.

@Stateless
@WebService
public class PersonService
{
   @PersistenceContext(name = "unit-name")
   private EntityManager entityManager;

   public Person create(Person person)
   {
      entityManager.persist(person);

      return person;
   }
}

现在客户端尝试更新人员,这就是我,JPA显示其不一致的地方.

public Person update(Person person)
{
   Person existingPerson = entityManager.find(Person.class,person.getEmail());

   // some logic with existingPerson
   // ...      

   // At this point existingPerson.readOnly is not null and it can't be null
   // due to the database.
   // The field is not updatable.
   // Person object has readOnly field equal to null as it was not passed 
   // via SOAP request.
   // And now we do merge.

   entityManager.merge(person);

   // At this point existingPerson.getReadOnlyValue() 
   // will throw NullPointerException. 
   // And it throws during marshalling.
   // It is because now existingPerson.readOnly == person.readOnly and thus null.
   // But it won't affect database anyhow because of (updatable = false)

   return existingPerson;
}

为了避免这个问题,我需要为readOnly对象公开set,并在合并之前执行类似的操作.

Person existingPerson = entityManager.find(Person.class,person.getEmail());
person.setReadOnlyObject(existingPerson.getReadOnlyObject()); // Arghhh!

我的问题：

>这是一个功能还是只是
不一致？
>你好吗？
你)处理这种情况？请
不建议我使用DTO.