hibernate ORM search an entity using oneToMany List of objects-CodePudding

I have the following entities.

@Entity
public class Blog{
  @Id
  Long id;
  @Column
  String name;
  @Column
  String datePosted;
  @OneToOne(orphanRemoval=true,cascade=CascadeType.ALL)
  Metadata metadata;
}

@Entity
public class Metadata{
    @Id
    Long id;
    OneToMany(orphanRemoval=true,cascade=CascadeType.ALL)
    List<Category> categories;
}

@Entity
public class Category{
    @Id
    Long id;
    @Column
    String name;
    @Column
    Sting type;
}

Now I have list of Categories so like this:

List<Category> categories;

Assume that the above list contains values; I want to search Blog using categories. Could you help me how to go about that?

CodePudding user response：

Based on my understanding, you will firstly need to fix your connections. To begin with, you will have to add this to the class Blog (metadata_id should be replaced with the name of the respective database field):

 @OneToOne(cascade = CascadeType.ALL)
 @JoinColumn(name = "metadata_id", referencedColumnName = "id")
 Metadata metadata;

Also, you will need this statement to the class Metadata:

 @OneToOne(mappedBy = "metadata")
 private Blog blog;

Now that you have a correct one to one connection between Blog and Metadata (Blog has a foreign key of the Metadata PK), you will have to create a many-to-one and one-to-many connection between the classes: Metadata and Category.

Based on my understanding, one Metadata has a lot of Categories, so you should add this to the class Metadata:

 @OneToMany(mappedBy="metadataFK")
 List<Category> categories;

Also you will have to add this to the class Category:

 @ManyToOne
 @JoinColumn(name="metadata_id")
 private Metadata metadataFK;

After you do all these you should be fine. I am not entirely sure about your question, but I suspect that you will have to use SQL (or HQL) to access Blogs through the Categories.

CodePudding user response：

I am trying to do the following:

private static List fingByCategory(List categories) { Session session = getSessionFactory().openSession();

    String hql = "from Blog b join fetch b.metadata.categories c where c in     :categories";       
Query query = session.createQuery(hql, Blog.class);
     query.setParameter("categories", categories);
    List<Blog> blogs = query.getResultList();
    session.close();
    return blogs;
}

But getting error: java.lang.IllegalStateException: org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance beforeQuery flushing: test.hb.Category

All the oneToOn and ManyToOne or oneToMany relationships are marked as (cascade = CascadeType.ALL) Could you help me what I am doing wrong?