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AndreasGelever
 Post subject: Use Map<Entity, Integer> to map many-to-many relation
PostPosted: Sat Nov 05, 2016 2:38 pm 
Newbie

Joined: Sat Nov 05, 2016 2:22 pm
Posts: 2
Hi, all!

I've been struggling figuring out whether it is possible to map this relational model:
Image
https://drive.google.com/open?id=0B32rkhYCEyjuenpKWlFaTGczSlE

to an object model like this:
Image
https://drive.google.com/open?id=0B32rkhYCEyjuZ3VpYzRGcDl2Nk0

I wanna store in the Map<Dish, Integer> pairs of Dish/Quantity, that I will get from the joining table "dish_order".


I studied this user's guide..http://docs.jboss.org/hibernate/orm/5.2/userguide/html_single/Hibernate_User_Guide.html#collections-map but still haven't arrived at the solution.

I tried this, but keep getting errors of different kind:
Code:
        @ElementCollection
        @CollectionTable(name = "order_dish")
        @Column(name = "quantity")
        @MapKeyJoinColumn(name = "D_ID", referencedColumnName = "ORD_ID")
        @Fetch(FetchMode.JOIN)
        Map<Dish, Integer> dishes;
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AndreasGelever
 Post subject: Re: Use Map<Entity, Integer> to map many-to-many relation
PostPosted: Sun Nov 06, 2016 3:16 am 
Newbie

Joined: Sat Nov 05, 2016 2:22 pm
Posts: 2
I've found one solution:

Code:
        @ElementCollection(fetch = FetchType.EAGER)
        @CollectionTable(name = "order_dish",
                joinColumns = @JoinColumn(name = "ORD_ID"))
        @MapKeyJoinColumn(name = "D_ID")
        @Column(name = "quantity")
        Map<Dish, Integer> dishes;


But the question remains: is this approach accepted, elegant and contains no pitfalls?
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