Mapping question

Page · **Joined:** Fri Sep 15, 2006 2:15 am **Posts:** 2

I'm new to Hibernate so I feel some difficulties with mapping of these tables:

FORM {FORM_ID, DESCRIPTION,...},
QUESTION {QUESTION_ID, DESCRIPTION,...},
QUESTION_GROUP {GROUP_ID, DESCRIPTION,...},
FORM_QUESTION {FORM_ID, QUESTION_ID, GROUP_ID}

As you can see the last table is not business entity but relation table (FORM_ID & QUESTION_ID are Primary Key, GROUP_ID is FK).

How should I map my entities Form, Question & QuestionGroup? Should I create some 'FormQuestion' entity? I wouldn't like to do it..

Thanks for any advice.

gert · **Joined:** Thu Jan 19, 2006 4:29 pm **Posts:** 348

Page wrote:

I'm new to Hibernate so I feel some difficulties with mapping of these tables:

FORM {FORM_ID, DESCRIPTION,...},
QUESTION {QUESTION_ID, DESCRIPTION,...},
QUESTION_GROUP {GROUP_ID, DESCRIPTION,...},
FORM_QUESTION {FORM_ID, QUESTION_ID, GROUP_ID}

As you can see the last table is not business entity but relation table (FORM_ID & QUESTION_ID are Primary Key, GROUP_ID is FK).

How should I map my entities Form, Question & QuestionGroup? Should I create some 'FormQuestion' entity? I wouldn't like to do it..

If You do not create 'FormQuestion' entity, how would You gain access to Group_Id (in code)? In UML world, the FormQAuestion could be association class

Gert

Page · **Joined:** Fri Sep 15, 2006 2:15 am **Posts:** 2

Oh, yes.. I see now...

And what about the relation table which contains only composite PK fields?
For ex. QUESTION_ID, FORM_ID & GROUP_ID fields are PK?

Thanks for response

gert · **Joined:** Thu Jan 19, 2006 4:29 pm **Posts:** 348

Page wrote:

And what about the relation table which contains only composite PK fields?
For ex. QUESTION_ID, FORM_ID & GROUP_ID fields are PK?

From code point of view, without association class it would mean something like

Code:

class Form
{
 IList<Question> Questions;
 IList<QuestionGroup> QuestionGroups;
}

class Question
{
 IList<Form> Forms;
 IList<QuestionGroup> QuestionGroups;
}

class QuestionGroup
{
 IList<Form> Forms;
 IList<Question> Questions;
}

How could You understand that for given form, in which group the question number 0 belongs to?

Edit: Not to mention that above class structure would be impossible to map into proposed table.

Gert