Question

我试图从一个表中检索一个实体列表，其中包含两个主键，每个主键都是一个外键的ID。

MySQL表：

绘画表：

id - int, PK, Auto increment
name - varchar(45)

图片表：

id - int, PK, Auto increment
name - varchar(45)
location - varchar(45)

painting_to_picture_link table：

painting_id - int, FK to id in painting
picture_id -  int, FK to id in painting
I've set primary key (painting_id, picture_id)
and set them to their foreign keys also as written above.

在Java中：

Painting.java

@Entity
@Table(name = "paintings")
public class Painting {
    @Id
    @GeneratedValue
    @Column(name = "id")
    private int id;

    @Column(name = "name")
    private String name;           

    ...
}

Picture.java

@Entity
@Table(name = "pictures")
public class Pictures {
    @Id
    @GeneratedValue
    @Column(name = "id")
    private int id;

    @Column(name = "name")
    private String name;           

    @Column(name = "location")
    private String location;   
    ...
}

PaintingPictureLink.class

   public class PaintingPictureLink implements Serializable {

    @<SOME ANNOTATION HERE>
    private Painting painting;

    @<SOME ANNOTATION HERE>
    private Picture picture;
    ...
   }

我见过很多例子，但对我来说并不适用。我尝试过@Id注释，@ EmbeddedId等等......没有工作。我得到的错误是表没有映射，无法确定模型的类型，缺少@Id注释...：|

非常感谢您查询此表并获取PaintingPictureLink列表。

我遵循的一些例子：

https://access.redhat.com/documentation/en-US/JBoss_Enterprise_Web_Server/1.0/html/Hibernate_Annotations_Reference_Guide/ch03s02s06.html

Using an Entity (and their Primary Key) as another Entity's Id

谢谢，

盖

Answer 1

DERP

找到了解决方案。

我创建了一个主键类：

@Embeddable
public class PicturePaintingPK implements Serializable {
    @ManyToOne
    private Painting painting;

    @ManyToOne
    private Picture picture;

    public PicturePaintingPK() {}

    // getters and setters //        
}

在PicturePaintingLink类中：

   @Entity
   @Table(name = "painting_to_picture_link")
   public class PaintingPictureLink implements Serializable {

        @Id
        private PicturePaintingPK primaryKey = new PicturePaintingPK()

        ...
        //constructor//
        ...

        public TTPK getPrimaryKey() {
            return primaryKey;
        }

        public void setPrimaryKey(TTPK primaryKey) {
            this.primaryKey = primaryKey;
        }

        // ... all the other getters and setters needed .... //
   }

此解决方案的来源是：

Example from Hibernate forum

盖

使用Java Hibernate将复合主键映射到外键实体

1 个答案: