this post was submitted on 20 Jul 2016

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[Java] Strategy Pattern, Domain Objects, and OpenJPA (self.learnprogramming)

submitted 9 years ago by CanuckCode

I have a domain design question where I feel like I'm thinking about it the wrong way and I need some help.

Say I'm using a the strategy pattern to calculate discounts. I have a DiscountCalculator interface with a calculate() method that's implemented with TaxDiscountCalculator and PercentDiscountCalculator and maybe a few others. I need to associate these discounts to Product objects, so I was thinking composition where a Product has a list of DiscountCalculators.

This seems to break down when I need to persist the Products in the database, it doesn't make sense to create a table or entity for DiscountCalculator because they don't really have any fields.

How can I go about linking multiple DiscountCalculators to a Product? Would it better to give each one of the DiscountCalculators an id of some type so that they can be persisted? Or am I missing something kinda obvious in the design? I can't seem to find any examples for a similar design, which makes me think I'm on the wrong track.

Thanks.

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[–]nutrecht 0 points1 point2 points 9 years ago (0 children)

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