CODEWITHSUNDEEP
javamysqlhibernatejpajoin
sp00m
sp00m

Reputation: 48837

JOIN not generated by Hibernate when first fetch-joining then simple-joining

Given the following entities:

@Entity
public class User {

  @Id
  private Long id;

  private String name;

  @OneToMany(mappedBy = "user", fetch = LAZY)
  private Set<UserRole> userRoles = new HashSet<>();

}

@Entity
public class UserRole {

  @Id
  private Long id;

  private String name;

  @ManyToOne(fetch = LAZY)
  private User user;

  @ManyToMany(fetch = LAZY)
  private Set<Article> articles = new HashSet<>();

}

@Entity
public class Article {

  @Id
  private Long id;

  private String name;

  @ManyToMany(mappedBy = "articles", fetch = LAZY)
  private Set<UserRole> userRoles = new HashSet<>();

}

I'm building the following query:

From<?, ?> root = query.from(User.class);
From<?, ?> joinedUserRoles = (From<?, ?>) root.fetch("userRoles", JoinType.INNER);
From<?, ?> joinedArticles = joinedUserRoles.join("articles", JoinType.INNER);
query.where(joinedArticles.in(someArticles));

The idea is to fetch-join User#userRoles while simple-joining UserRole#articles. The problem is that the generated query is invalid:

select
    user0_.id as id1_6_0_,
    userroles1_.id as id1_7_1_,
    user0_.name as name5_6_0_,
    userroles1_.role as role2_7_1_,
    userroles1_.user_id as User_i3_7_1_,
    userroles1_.user_id as User_i3_7_0__,
    userroles1_.id as id1_7_0__ 
from
    User user0_ 
inner join
    UserRole userroles1_ 
        on user0_.id=userroles1_.user_id 
where
    generatedAlias2 in (
        ?
    )

Thrown error:

SQLSyntaxErrorException: Unknown column 'generatedAlias2' in 'where clause'

Indeed, JPA/Hibernate did not generated the simple-join UserRole#articles for some reason.

Any idea what's happening?

I'm on Hibernate 5.2.16.

Upvotes: 2

Views: 245

Answers (2)

K.Nicholas
K.Nicholas

Reputation: 11561

Looked again: What's wrong with this? Seems to work.

CriteriaQuery<User> cq = cb.createQuery(User.class);
Root<User> user = cq.from(User.class);
Join<User, UserRole> userRoles = user.join("userRoles", JoinType.INNER);
Join<UserRole, Article> articles = userRoles.join("articles", JoinType.INNER);
cq.where(articles.in(Arrays.asList(new Long[]{1L})));

Upvotes: 0

Karol Dowbecki
Karol Dowbecki

Reputation: 44980

As per Batch fetching - optimizing object graph loading:

JPQL does not allow the aliasing of the join fetch, so if you wish to also query on the relationship, you have to join it twice.

An example why this is prohibited is given in this answer.

Your casting allows to construct the criteria object however the provider doesn't seem to understand it properly and fails to resolve the articles alias.

Replacing the fetch() with join() might not be ideal in terms of loading lazy relationships but should construct a valid query.

Upvotes: 2

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