How do you decide in which entity classes to put JPA NamedQuery annotations?

Say I have a Customer - CustomerOrder one-to-many bi-directional relationship with the CustomerOrder holding the total value of each order.

If I had a qu开发者_StackOverflow社区ery to find the total value of all orders for a particular customer :

select SUM(o.orderValue) from CustomerOrder o where o.customer = :customer

Does it matter in which entity class this is annotated? Why would you put it in one or the other?

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Does it matter in which entity class this is annotated?

From a technical point of view, it doesn't matter as you will use the name of a @NamedQuery to call it.

Why would you put it in one or the other?

But, from a "logical" point of view, putting the @NamedQuery where is "naturally" belongs will definitely ease the maintenance. In your example, I would put the query in the CustomerOrder entity because the query is about finding CustomerOrder, this is just where I'd expect to find it if I had to look for it.

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It doesn't matter. The general principle is to put it where it belongs logically. In your case - it'd better be in CustomerOrder

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Put them in the XML mapping files which should be declared in the persistence.xml. See this great link: arjan-tijms.omnifaces.org/2010/09/where-to-put-named-queries-in-jpa

Lots of queries do not 'naturally' belong with the entity (and further you have to modify the entity code, if you put them there, each time you need a new query).