CODEWITHSUNDEEP
javahibernatejoinmany-to-many
Davidsun
Davidsun

Reputation: 721

Hibernate Many-to-many with eager load problems

My definition of class is like:

@Entity
@Table(name = "items")
public class Item {
    @Id
    @GeneratedValue
    private long id;

    @Column(unique = true, nullable = false)
    private String url;

    @ManyToMany(fetch = FetchType.EAGER)
    @Fetch(FetchMode.JOIN)
    private Collection<Tag> tags;

    @Column(columnDefinition = "TEXT")
    private String text;
}

and when fetching with

 itemSession.createQuery("from Item i where i.url=?").setString(0, url)

two SQL queries are needed:

select item0_.id as id1_,
       item0_.text as text1_, 
       item0_.url as url1_ 
   from items item0_ 
   where item0_.url=?

select tags0_.items_id as items1_1_1_, 
       tags0_.tags_id as tags2_1_,
       tag1_.id as id0_0_, tag1_.lastCrawlTime as lastCraw2_0_0_, 
       tag1_.name as name0_0_ 
  from items_tags tags0_ inner join tags tag1_ on tags0_.tags_id=tag1_.id 
  where tags0_.items_id=?

How can I make it into one?

Upvotes: 3

Views: 1719

Answers (1)

dcernahoschi
dcernahoschi

Reputation: 15240

HQL ignores the fetching strategy specified in mappings. You should force the join using 

"from Item i join fetch i.tags where i.url=?"

Upvotes: 2

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