Modelling a manyToMany relationship with attributes

Question

I have a ManyToMany relationship between two classes, for instance class Customer and class Item. A customer can buy several items and an item can be bought by different customers. I need to store extra information in this relationship, for example the day when the item was bought. I wonder how is this usually modelled in JPA, cause I'm not sure how to express this in code. Do I have to create a new class to model all the attributes of the relationship and make a manyToMany relationship between the other classes or is a better way to do this?

Thanks

OK, as I see I need an extra class. I there any naming convention for this type of classes? — Javi, May 31 '10 at 11:48

score 3 · Accepted Answer · answered May 31 '10 at 11:42

3

The recommended way is to create a new association class to store the needed attributes, and two one-to-many associations to the two parties involved.

answered May 31 '10 at 11:42

Péter Török

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score 1 · Answer 2 · answered May 31 '10 at 11:43

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I guess you will indeed have to create a new class for the relationship.

answered May 31 '10 at 11:43

Maurice Perry

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score 1 · Answer 3 · answered May 31 '10 at 11:43

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Like you said yourself, the correct way is to create a new class with the additional attributes.

answered May 31 '10 at 11:43

KCL

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Modelling a manyToMany relationship with attributes

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