java - Hibernate继承、Collections和@OrderedBy父类(super class)属性产生MySQL语法错误

Question

我使用 Hibernate 3.6.1 映射三个实体

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
public class Entry {
   private Long id; 
   private Date publishedAt; 

   @Id
   public getId() {...}

   ...
}

@Entity
public class Category {
   private Long id; 

   List<Podcast> podcasts;

   @Id
   public getId() {...}

   @OneToMany(mappedBy = "category", cascade = {CascadeType.ALL}, fetch = FetchType.EAGER)
   @OrderBy("publishedAt")
   public List<Podcast> getPodcasts() {
      return podcasts;
   }
}

和

@Entity
public class Podcast extends Entry {

   private Category category; 

   @ManyToOne(fetch = FetchType.EAGER)
   public PodcastsCategory getCategory() {
      return category;
   }
}

如果我尝试获取一个 Category 实例，我会得到一个异常

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'podcasts0_.Entry.publishedAt' in 'order clause'

是什么导致了这个异常？这个映射有什么问题？

Answer 1

这是由以下错误引起的:HHH-3577 Wrong SQL in order by clause when using joined subclasses .

作为解决方法，您可以删除 podcasts 上的 @OrderBy 和 fetch = FetchType.EAGER 并使用以下查询而不是 获取():

SELECT DISTINCT c 
FROM Category c LEFT JOIN FETCH c.podcasts p
WHERE c.id = ?
ORDER BY p.publishedAt