Question

我有一些Hibernate / JPA注释（但实际上并不知道区别）允许我创建一个关联类。此类将两个与一个对象相关的项组合在一起。我最初使用@JoinTable，但意识到我需要更多关于元数据的元数据，因此必须将代码转换为另一种对象类型。

目前我使用@Id标记我的对象的ID列，并使用@NaturalId (mutable = false)标记String uuid。

我的关联类正在使用@ManyToOne并且创建表很好，但是当我查看它时，表使用@Id字段作为映射列。我更希望这个关联类使用@NaturalId uuid来轻松地将关系/关联转移到其他系统。

如何让关系使用正确的标识符？

作为参考，我的数据库和Java代码如下所示：

AssociationsTable
----------------------------------------------
| ID | META DATA | ID ASSOC. 1 | ID ASSOC. 2 |
----------------------------------------------
| 1  |  stuff    |    1        |     2       |
----------------------------------------------

Objects
------------------------------
| ID | META DATA | UUID      | 
------------------------------
| 1  |  stuff    |  FOO-123  |
------------------------------
| 2  |  stuff    |  BAR-456  |
------------------------------

Association Class{
  ObjA main;
  ObjA sub;

  @ManyToOne
  getMain()

  @ManyToOne
  getSub()
}

ObjA Class{
  Long id;
  @Id
  @GeneratedValue(generator="increment")
  @GenericGenerator(name="increment", strategy = "increment")
  @XmlElement
  @Column(name = "ID", unique = true, nullable = false)
  getId()

  String uuid;    
  @NaturalId (mutable = false)
  @GeneratedValue(generator = "uuid")
  @GenericGenerator(name = "uuid", strategy = "uuid2")
  @Column(name = "uuid", unique = true)
  getUUID()
}

Answer 1

您可以使用referencedColumnName的{{1}}属性，如上所述here。因此，对于您的示例，映射应如下所示：

<强> ObjA.java：

@JoinColumn

<强> Association.java：

package hello;

import org.hibernate.annotations.NaturalId;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

@Entity
public class ObjA {
    Long id;
    String uuid;

    public ObjA() {
    }

    public ObjA(String uuid) {
        this.uuid = uuid;
    }

    @Id
    @GeneratedValue
    @Column(name = "obj_a_id", unique = true, nullable = false)
    Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    @NaturalId(mutable = false)
    @Column(name = "uuid", unique = true, nullable = false)
    public String getUuid() {
        return uuid;
    }

    public void setUuid(String uuid) {
        this.uuid = uuid;
    }
}

已成功测试这些映射，以存储package hello; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.ManyToOne; @Entity public class Association { Long id; ObjA main; ObjA sub; public Association() { } public Association(ObjA main, ObjA sub) { this.main = main; this.sub = sub; } @Id @GeneratedValue @Column(name = "association_id", unique = true, nullable = false) Long getId() { return id; } public void setId(Long id) { this.id = id; } @ManyToOne @JoinColumn(name = "main_uuid", referencedColumnName = "uuid", nullable = false) public ObjA getMain() { return main; } public void setMain(ObjA main) { this.main = main; } @ManyToOne @JoinColumn(name = "sub_uuid", referencedColumnName = "uuid", nullable = false) public ObjA getSub() { return sub; } public void setSub(ObjA sub) { this.sub = sub; } }表的uuid和obja列中main_uuid表的sub_uuid列的值。这是针对PostgreSQL 9.4.4使用association，org.hibernate.common:hibernate-commons-annotations:4.0.5.Final，org.hibernate.javax.persistence:hibernate-jpa-2.1-api:1.0.0.Final和org.hibernate:hibernate-core:4.3.10.Final进行测试的。

Hibernate @ManyToOne引用类使用@NaturalId而不是@Id

1 个答案: