Question

我是JPA的新手。我有一个我认为是一个非常简单的例子，但我在实现它时遇到了麻烦。基本上，我有一个我想在其他实体中“重用”的实体。

我有一个User有两个字段 - Home和Office。其中每一个都依次引用Address，如下所示：

@Entity
public class User extends Model {

    @Column 
    private String name;

    @OneToOne
    private Home home;

    @OneToOne
    private Office office;

}

@Entity
public class Home extends Model {

    @OneToOne
    private Address address;

    @OneToOne(mappedBy="home")
    private User user;

    // ...

}

@Entity
public class Office extends Model {

    @OneToOne
    private Address address;

    @OneToOne(mappedBy = "office")
    private User user;

    // ...
}

@Entity
public class Address extends Model {

    @Column
    private String line1;

    @Column 
    private String line2;

    @Column
    private String city;

    /*
     * Is this possible? Being owned by two entities?
     */


    @OneToOne(mappedBy="address")
    private Home home;

    @OneToOne(mappedBy="address")
    private Office office;

    // ...
}

我如何实现这一目标？

修改

我最初遇到这个例外：

org.hibernate.AnnotationException: @OneToOne or @ManyToOne on example.Home.address references an unknown entity: example.Address

事实证明，其中一个类已从@Entity而非org.hibernate导入javax.persistence注释。解决这个问题后，最初的例外消失了（this帮助我确定了问题）

但是，我现在有一个新例外：

org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: example.User.home -> example.Home

我对此并不十分了解。我应该在save实例之前调用Home User对象吗？

Answer 1

我通过向所有实体中的所有cascade=CascadeType.ALL注释添加@OnetoOne属性来解决问题。

如果没有此注释，在保存拥有之前，我必须save每个拥有的实体。例如，在保存住所属的Home之前，我必须先保存User。

将cascade属性添加到注释会为您解决此问题。您只需保存User即可自动为您保存Home和Address。

This帖子帮我解决了这个问题。

Answer 2

你能只做一个用户：

@Entity public class User extends Model   
      {        
         @Column      
         private String name;

         @Embedded
         @AttributeOverrides({
            @AttributeOverride(name = "line1", column = @Column(name="column11")),
            @AttributeOverride(name = "line2", column = @Column(name="column21")),
            @AttributeOverride(name = "city", column = @Column(name="column31"))
         })     
         private Address homeAddress;        

         @Embedded
         @AttributeOverrides({
            @AttributeOverride(name = "line1", column = @Column(name="column12")),
            @AttributeOverride(name = "line2", column = @Column(name="column22")),
            @AttributeOverride(name = "city", column = @Column(name="column32"))
         })
         private Address officeAddress;

         // .. setters, getters
      }    

      @Embeddable 
      public class Address extends Model   
      {   
          private String line1;       
          private String line2;       
          private String city;  
         // .. getters, setters  
   }

OneToOne从多个拥有实体映射到实体

修改

2 个答案: