Question

I’m trying to annotate this :

public class                        Keyword {
    @Id @GeneratedValue
    private Integer                 id;
    //Missing annotation
    private Map<Keyword, Integer>   keywordRelated;
}

I found this example but they don’t deliver the relational model, and it’s not the exactly same model. And I can’t figure out how their tables are.

Answer 1

Following tells only how to map Map which does have entity as a key (depending about case can be that there is better solutions, like intermediate object with ratio).

@ElementCollection is designed for mapping such a collection. @OneToMany cannot be used when value is not entity.

By default following mapping

@ElementCollection
private Map<Keyword, Integer> keywordRelated;

Maps to following table in database (assuming that name of table for Keyword entity is Keyword and not affected via @Table-annotation):

Keyword_KEYWORDRELATED (
  Keyword_ID (PK, FK to Keyword ID), 
  KEYWORDRELATED , 
  keywordRelated_KEY (FK to Keyword ID)
)

If default naming for database tables and columns is not sufficient, those can be customized as follows:

@ElementCollection
@CollectionTable(name= "keyword_to_related_keyword")
@Column(name="ratio")
@MapKeyColumn(name="related_keyword_id")
@MapKeyJoinColumn(name="some_other_preferred_name")
public Map<Keyword, Integer> keywordRelated;