CODEWITHSUNDEEP
javahibernatecriteria
MDP
MDP

Reputation: 4267

Nested createAlias() in Hibernate

I have to make a particular query using Hibernate.

The following classes are just a simple example, to make easier for you to understand my scenario and my goal. I made up the example while writing this post, I hope I didn't make errors (anyway don't pay attention to the errors :D).

class Father{
  int id;

  @OneToMany(mappedBy = "father", fetch = FetchType.LAZY)
  List<Son> sonList;
}

class Son{
 @ManyToOne(targetEntity=Father.class)  
 @JoinColumn(referencedColumnName = "id", name = "father")
 Father father;

 @OneToMany(mappedBy = "son", fetch = FetchType.LAZY)
 List<Toy> toyList;
}

class Toy{
 @ManyToOne(targetEntity=Son.class) 
 @JoinColumn(referencedColumnName = "id", name = "son")
 Son son;

 @OneToMany(mappedBy = "Feature", fetch = FetchType.LAZY)
 List<Feature> featureList;
}

class Feature{
 @ManyToOne(targetEntity=Toy.class)
 @JoinColumn(referencedColumnName = "id", name = "toy") 
 Toy toy;

 boolean unisex;
}

I have to select from the database a Father with id = 1, with his relative Son, but only the sons that has a Toy with Feature.unisex = true.

I dunno how to reach the field Feature.unisex of class Toy.

With createAlias() I can do:

Criteria criteria = session.createCriteria(Father.class);           
criteria.createAlias("sonList", "sonListAlias");
criteria.add(Restrictions.idEq(1));
criteria.add(Restrictions.in("sonListAlias.toyList", toyList));

but I can't go further. I should need something like: 

Criteria criteria = session.createCriteria(Father.class);           
criteria.createAlias("sonList", "sonListAlias");
criteria.add(Restrictions.in("sonListAlias.toyList.featureList.unisex", unisex));

but, of course, this is not the right way to do it.

Thank you in advance.

Upvotes: 1

Views: 1145

Answers (1)

v.ladynev
v.ladynev

Reputation: 19956

Firstly, please don't use unnecessary mapping properties. I mean targetEntity=Father.class, referencedColumnName = "id", name = "father". And don't use names like sonList, just sons.

Criteria criteria = session.createCriteria(Father.class);           
criteria.createAlias("sonList", "son");
criteria.createAlias("son.toyList", "toy");
criteria.createAlias("toy.featureList", "feature");
criteria.add(Restrictions.idEq(1));
criteria.add(Restrictions.eq("feature.unisex", true));

If you need to eagerly fetch sonList, you can try to use setFetchMode("sonList", FetchMode.JOIN).

If you need to

"always" get a father and get only his sons that have toys that have Feature.unisex = true

you can try to use @Filter

Hibernate @Filter and @FilterJoinTable Annotation Example

But I think It will be better, if you load sonList in a separate request

    Criteria criteria = session.createCriteria(Son.class);           
    criteria.createAlias("father", "father");
    criteria.createAlias("toyList", "toy");
    criteria.createAlias("toy.featureList", "feature");
    criteria.add(Restrictions.eq("father.id", 1));
    criteria.add(Restrictions.eq("feature.unisex", true));

Upvotes: 2

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