CODEWITHSUNDEEP
javahibernatespring-mvcjpa
Suryavanshi
Suryavanshi

Reputation: 605

How to add a HashMap<Object, String> in an entity class?

I am trying to create a sample Report card application and want to persist a map between subject and student's grade This is my scorecard class:

@Entity
public class ScoreCard {
    @NotNull @ElementCollection @ManyToMany(cascade=CascadeType.ALL)
    private Map<Subject, String> gradesForMainSubject = new HashMap<Subject, String>();
}

But when trying to save data I always end up with 

Caused by: org.hibernate.AnnotationException: Use of @OneToMany or @ManyToMany targeting an unmapped class: gradesForMainSubject

Subject itself is a Managed entity (annotated by @Entity). Any suggestions on how can I move forward.

Upvotes: 2

Views: 3372

Answers (1)

Ish
Ish

Reputation: 4154

You cannot use both @ElementCollection and @ManyToMany at the same time for a collection field.

If the values of your collection are entities, then you can use either one of the 2: @OneToMany or @ManyToMany

If the values of your collection are non-entities, then you must use @ElementCollection.

In your case, the values of your map are String which are not entities. Therefore you need to use @ElementCollection. Remove the @ManyToMany mapping. This rule should be followed, regardless of whether you map key is an entity or not.

Upvotes: 4

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