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?

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.

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

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).