Persisting a domain model with Hibernate 3 - POJOs in Action: Developing Enterprise Applications with Lightweight Frameworks - page 238

in the O/R mapping and only uses SQL joins for those relationships specified by
fetch joins.
Let's look at how the code for the Place Order use case can use fetch joins.
Instead of loading the PendingOrder by calling Session.load() , the PendingOrder-
Repository methods called by PlaceOrderService method must load the Pending-
Order and the required related objects by executing a query that uses fetch joins.
When updating the payment information, the PlaceOrderService would call the
following method to load the pending order:
public class HibernatePendingOrderRepositoryImpl {
…
public PendingOrder
findPendingOrderWithRestaurantLineItemsAndMenuItems(
String pendingOrderId) {
return (PendingOrder) getHibernateTemplate()
.findByNamedQuery(
"PendingOrder.
bbbbbb bb ➥ findPendingOrderWithRestaurantLineItemsAndMenuItems",
new Integer(pendingOrderId))
.get(0);
}
}
<hibernate-mapping>
…
<query name="PendingOrder.
bbbbbbb b ➥ findPendingOrderWithRestaurantLineItemsAndMenuItems">
<![CDATA[
from PendingOrder po
left outer join fetch po.restaurant
left outer join fetch po.lineItems as lineItem
left outer join fetch lineItem.menuItem
where po.id = ?
]]></query>
…
</hibernate-mapping>
This code executes the named query, which uses fetch joins to eagerly load the
pending order's restaurant and its line item. Similarly, when updating the quanti-
ties the PlaceOrderService must call this method to load the pending order:
public class HibernatePendingOrderRepositoryImpl {
…
public PendingOrder findPendingOrderWithRestaurantAndMenuItems(
String pendingOrderId) {
return (PendingOrder) getHibernateTemplate()
.findByNamedQuery(