CODEWITHSUNDEEP
javahibernatemany-to-many
OemerA
OemerA

Reputation: 2672

Hibernate Many-to-Many relationship query

I have a class Person and each person can have documents with a specific language. The Person and Document classes are linked with a Many-To-Many relationship.

My Java code looks like this:

@Table(name="person")
public class Person {
  @Id
  @Column(name="id")
  private Long id;

  @Column(name="name")
  private String name;

  @ManyToMany(targetEntity=Document.class)
  @JoinTable(name="person_document",
    joinColumns={
      @JoinColumn(name="person_id")
    },
    inverseJoinColumns={
      @JoinColumn(name="document_id")
    }
  )
  private List<Document> documents;

  // getter and setter ....
}

public class Document {
  @Id
  @Column(name="id")
  private Long id;

  @Column(name="language")
  private String language;

  // getter and setter ...
}

NOTE: I'm using Hibernate 3 here.

I want to create a query which gives me back all persons with documents only in a specific language, say english.

My first attempt was following code

Session session = HibernateUtil.getSessionFactory().getCurrentSession();
session.beginTransaction();
session.createCriteria(Person.class)
  .createAlias("documents", "d")
  .add(Restrictions.eq("d.language", "english")
  .list();

This code lists just the people who have documents in english but I want all persons but only documents in english for each person.

For example:

I want to get listed:

Does that make sense? And if so how would a Hibernate query for such as query look like.

As that is really hard to get I'm thinking about this is the wrong way to do it but I don't know any other way to do it.

I appreciate your help!

Upvotes: 1

Views: 2090

Answers (1)

Niroshan Abayakoon
Niroshan Abayakoon

Reputation: 921

You should query vise versa. That means you should load documents which are in English and from that document objects you can get the persons. 

Session session = HibernateUtil.getSessionFactory().getCurrentSession();
session.beginTransaction();
session.createCriteria(Documentn.class)
  .createAlias("documents", "d")
  .add(Restriction.eq("d.language", "english")
  .list();

Upvotes: 2

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