Persisting a domain model with Hibernate 3 - POJOs in Action: Developing Enterprise Applications with Lightweight Frameworks - page 236

You can, for example, configure the PendingOrder - Restaurant and PendingOrder-
LineItem - MenuItem relationships to be eagerly loaded with an order as follows:

<hibernate-mapping>

<class name="PendingOrder"
table="PLACED_ORDER">
…
<many-to-one name="restaurant"
fetch="join"
column="RESTAURANT_ID"
…
/>
</class>

<class name="PendingOrderLineItem"
table="PLACED_ORDER">
…
<many-to-one name="MenuItem"
fetch="join"
column="RESTAURANT_ID"
/>
…
</class>

</hibernate-mapping>
The fetch="join" attribute of the mapping element for the PendingOrder - Restau-
rant relationship tells Hibernate to load a PendingOrder by executing a SQL
SELECT statement that does an outer join between the PENDING_ORDER and RES-
TAURANT tables to retrieve both the pending order and its restaurant. The
fetch="join" attribute for the PendingOrderLineItem - MenuItem has a similar
effect. With this configuration, calling Session.load() with the PendingOrder
class and a pending order id will load a pending order, its restaurant, its line
items, and their menu items using two SELECT statements. The first loads the
pending order and the restaurant, and the second loads the line items and their
menu items.
Although using the fetch attribute to configure eager loading for a relation-
ship might appear to be straightforward, there are a couple of important things to
remember. First, the fetch attribute only affects how objects are loaded by:

get() and load()

■

Navigation from one object to another

■

Criteria queries, which are described in detail in chapter 11

■