CODEWITHSUNDEEP
hibernate
user1836045
user1836045

Reputation: 31

Hibernate - How to reference a collection from a join table?

I've got a model where exam has a many to many mapping to questions, and each question_exam combination can have many results (for example question 1 in exam1 can be answered 10 times, therefore will have 10 results). The basic model classes are below

Exam{
    exam_id
}

Question{
    question_id
}    

Result{
id
    exam_id
    question_id
    dateentered
}

I can create the relationship between exam and questions easily, hibernate uses a join table I've created called exams_questions. My problem is linking results to the exams_questions table. For example if I want to get an exam object that has the following structure: Exam - Questions - Results (only for the questions related to the exam)

How do I write my mappings to allow my to get an Exam an as object with a collecton of questions, and those questions have collections of results (only for that exam)?

I've looked at join tables with extra columns and ternary associations but I don't think they provide me with what I need.

Thanks in advance

Upvotes: 3

Views: 262

Answers (1)

JB Nizet
JB Nizet

Reputation: 691695

You should have the following associations:

Exam {
    id;

    @OneToMany(mappedBy = "exam")
    Set<ExamQuestion> examQuestions;
}
Question {
    id;

    @OneToMany(mappedBy = "question")
    Set<ExamQuestion>;
}
ExamQuestion {
    id;

    @ManyToOne
    Question question;

    @ManyToOne
    Exam exam;

    @OneToMany(mappedBy="examQuestion")
    Set<Result> results;
}
Result {
    id

    @ManyToOne
    ExamQuestion examQuestion;
}

The above maps each association as a bidirectional association, but you could of course choose to makes them unidirectional.

Upvotes: 2

Related Questions