CODEWITHSUNDEEP
javahibernatehqlhibernate-criteria
Victor Ponomarenko
Victor Ponomarenko

Reputation: 490

Hibernate hql/criteria result contains collection

I have two entities:

public class Photo {
   Long id;
   String url;
   @ManyToOne
   @JoinColumn(name ="user_id")
   User user;
   // other fields and getters/setters
}

And second:

public class User {
   Long id;
   @OneToMany(mappedBy = "user")
   private Collection<Photo> photos;
   // other fields and getters/setters
}

I am trying to get this DTO:

public class UserDTO {
    Long id;
    List<String> photosUrls;
}

But I can't find the right solution. I wrote next criteria - find user with photos by login:

getCurrentSession().createCriteria(User.class, "user")
    .createAlias("user.photos", "photos")
    .setProjection(getUserProjection())
    .add(Restrictions.eq("user.login",login))
    .setResultTransformer(Transformers.aliasToBean(UserDTO.class))
    .list();
 // projection   
    getUserProjection() {
        return Projections.projectionList()
            .add(Projections.property("user.id"), "id")
            .add(Projections.property("photos"), "url");
    }

Also tried with HQL:

getCurrentSession()
    .createQuery("select u.id, p.url " +
        " from User u inner join u.photos p " +
        " where u.login LIKE :login")
    .setString("login", login)
    .list();

But returned result is List<Object[]> type but I need List<UserDTO>.

Update:

HTTP Status 500 - Request processing failed; nested exception is org.springframework.orm.hibernate4.HibernateSystemException: IllegalArgumentException occurred while calling setter for property [com.memories.dto.UserDTO.photos(expected type = java.util.List)]; target = [com.memories.dto.UserDTO.photos@4e162869], property value = [https://i1.sndcdn.com/artworks-000031744302-0730nk-t500x500.jpg] setter of com.memories.dto.UserDTO.photos; nested exception is IllegalArgumentException occurred while calling setter for property [com.memories.dto.UserDTO.photos] (expected type = java.util.List)]; target = [com.memories.dto.UserDTO.photos@4e162869], property value = [https://i1.sndcdn.com/artworks-000031744302-0730nk-t500x500.jpg]

Upvotes: 2

Views: 744

Answers (2)

Johnson Abraham
Johnson Abraham

Reputation: 781

I think with the above code all you have to do it is to assign the resultant directly to List and it should work like a breeze. something like this.

List<User> userList = yourCriteria.list();

Upvotes: 1

Victor Ponomarenko
Victor Ponomarenko

Reputation: 490

So, i found not the best solution, but...

Firstly, need to get list of entities User:

List<User> list = getCurrentSession()
                .createQuery("from USer as u where u.login LIKE :login")
                .setString("login", login)
                .list();

Next, we declare in entity User method like this one, which convert List<Photo> to List<String>:

public List<String> getPhotosUrls() {
    List<String> urls = new ArrayList<String>(photos.size());
    for (Photo p : photos)
        urls.add(p.getUrl()));
    return urls;
}

And last step is hard-coded creating DTO beans:

List<UserDTO> users = new ArrayList<UserDTO>(list.size());
for (User u : list) {
    users.add(new UserDTO(u.id, u.getPhotosUrls));

And, of course, you must have UserDTO(Long id, List<String> urls) constructor. If anybody will find better solution, pls write here :)

Upvotes: 0

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