database - 使用 @JoinTable 时出现 org.hibernate.exception.ConstraintViolationException

Question

这是我的数据库:

------------       ----------------------       ------------
|   NEWS   |       |     NEWS_IMAGE     |       |  IMAGE   |
------------       ----------------------       ------------
| id | text|       | id_news | id_image |       | id | URL |
------------       ----------------------       ------------
  |                      |       |                |
  <-<-<-<-<-<- Foreign Key       Foreign Key ->->->

在对象News 中，我有一个对象Image 的List。这是我的 map 系统:

@Entity
@Table(name = "news")
class News{

   @Id
   @GeneratedValue
   @Column(name = "id")
   private long id;

   @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, orphanRemoval = true)
   @JoinTable(name = "news_image",
              joinColumns = { @JoinColumn(name = "id_news")},
              inverseJoinColumns = { @JoinColumn(name = "id_image")})   
              private List<Image> images = new ArrayList<Image>();}

这是对象Image:

@Entity
@Table(name = "image")
public class Image {

   @Id
   @Column(name = "id")
   @GeneratedValue
   private long id;

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

这是我删除对象图像的方式:

News news  = org.hibernate.SessionFactory.get(News.class, id);
Image image = news.getImages().get(0);  
org.hibernate.SessionFactory.getCurrentSessionFactory().delete(image);

当我尝试从表 image 中删除图像时，出现此错误:

Could not execute JDBC batch update;
SQL [delete from image where id=?];
constraint [null]; nested exception is org.hibernate.exception.ConstraintViolationException:
Could not execute JDBC batch update.

如果我删除表news_image 到表image 的外键，一切正常； Hibernate 能够先删除表news_image 中的记录，然后再删除表image 中的记录。我应该怎么办？我应该删除那个外键吗？我是不是在映射时出错了，这就是我收到该错误的原因？

提前致谢。

Answer 1

就您的映射而言，Image 对与 News 的关联一无所知，因此 NEWS_IMAGE 关联表中的相应记录永远不会被 Hibernate 删除，因为它对此一无所知。

要解决此问题，您可以按以下方式更新代码:

//News is managing the association to Image and has Cascade options defined
//so we need to update and merge the News instance
News news  = org.hibernate.SessionFactory.get(News.class, id);
Image image = news.getImages().get(0);  
news.getImages().remove(image);
org.hibernate.SessionFactory.getCurrentSessionFactory().saveOrUpdate(news);

或者您可以更新您的映射，以便 Image 知道关联并像以前一样继续:

新闻:

@Entity
@Table(name = "news")
class News{

   @Id
   @GeneratedValue
   @Column(name = "id")
   private long id;

   @OneToMany(mappedBy = "news", cascade = CascadeType.ALL, fetch = FetchType.EAGER, orphanRemoval = true)
   private List<Image> images = new ArrayList<Image>();
}

图片:

@Entity
@Table(name = "image")
public class Image {

   @Id
   @Column(name = "id")
   @GeneratedValue
   private long id;

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

   @ManyToOne( cascade = CascadeType.DELETE)
   @JoinTable(name = "news_image",
              joinColumns = { @JoinColumn(name = "id_image")},
              inverseJoinColumns = { @JoinColumn(name = "id_news")})   
   private News news;

}