java - Hibernate多态性(扩展父类)

Question

关于 Hibernate 多态性和扩展父类(我不能直接修改)的问题。我的父类名为Contact:

@Entity 
@Table(name="contact")
@Inheritance(strategy=InheritanceType.JOINED) 
public class Contact {
  @Id @GeneratedValue(strategy=GenerationType.IDENTITY)
  public long id;
  public String name;
} 

子类称为 ContactLocation，它将 Location 与 Contact 相关联:

@Entity 
@Table(name="contact_location") 
@Inheritance(strategy=InheritanceType.JOINED) 
public class ContactLocation extends Contact {
  @ManyToOne(targetEntity=Location.class, cascade=CascadeType.ALL)
  Location location;
}

生成的数据库表结构似乎是正确的:

contact: 
 id:long 
 name:varchar

contact_location: 
 contact_id:long 
 location_id:long

这是我的保存方法，我需要更新现有的ContactLocation，或为现有的联系人保存新的ContactLocation:

public void saveContact(Object dialog) { 
  Contact contact = ui.getAttachedObject(dialog, Contact.class); 
  ContactLocation contactLocation = null; 
  if (contact instanceof ContactLocation) { 
     LOG.debug("Casting Contact to ContactLocation"); 
     contactLocation = (ContactLocation)contact; 
     //TODO Update existing ContactLocation
     //UPDATE contact_location SET location_id = 33 WHERE contact_id = 22;
  } 
  else { 
     LOG.debug("Contact NOT instanceof ContactLocation"); 
     //TODO Save new ContactLocation from existing Contact
     //INSERT INTO contact_location (contact_id, location_id) VALUES (22,33);
  }
}

如何使用我的 ContactLocationDao 在 contact_location 表中创建一行，将 Contact 映射到 Location？

Answer 1

据我所知，不支持对象在创建后更改类型。恐怕您必须创建一个新的 ContactLocation 对象，更新可能的引用，然后删除原始联系人。