Hibernate: Map Two Columns to a HashMap's Key and Value

Thomas Stubbe :

I have a database with an object, which has translations.

There are 2 tables: table Object which has id and more properties and table 'object_translation' which has object_id, language (varchar) and translation (varchar)

I would like to map this to

public class Object {
    private Map<Language, String> translations
}

Where language is an enum in code and a string in the DB.

Is this possible with annotations? or do I need to create either Collection<QuestionTranslation> or write my own hibernate mapping functions in the DAO (I'm using spring-data, so I would prefer to keep it nice and clean as interfaces and annotations)

Versions: spring-boot 2 with provided hibernate from spring-boot-starter:

spring boot: <version>2.0.3.RELEASE</version>
<hibernate.version>5.2.17.Final</hibernate.version>
<hibernate-jpa-2.1-api.version>1.0.2.Final</hibernate-jpa-2.1-api.version>

So far I have this:

@OneToMany
@JoinTable(name = "object_translation", joinColumns = {@JoinColumn(name = "object_id", referencedColumnName = "id")})
@MapKey(name = "language")
@MapKeyEnumerated(EnumType.STRING)
private Map<Language, String> translations;

But how do I map the value as well? (for clarification: the String value should be the translation column in the DB)

Because I don't have a primary-key, this should theoretically be possible?

Thanks in advance!

Thomas Stubbe :

I managed to fix it =)

You shouldn't use @OneToMany.

What I used:

public class Object {

    @ElementCollection(fetch = FetchType.EAGER)
    @CollectionTable(name = "object_translation",
                 foreignKey = @ForeignKey(value = ConstraintMode.CONSTRAINT, name = "fk_object_translation_object"),
                 joinColumns = @JoinColumn(name = "object_id"))
    @MapKeyColumn(name = "language", nullable = false)
    @MapKeyEnumerated(EnumType.STRING)
    @Column(name = "translation", nullable = false)
    private Map<Language, String> translations;
}