Java Reference
In-Depth Information
Listing 10.5. Relationships in the
Item
entity
By default, some of the relationship types are retrieved lazily and some are loaded eagerly.
We'll discuss why each default makes sense as we go through each relationship retrieval
case for the
Item
entity. The
Seller
associated with an
Item
is retrieved eagerly, be-
cause the fetch mode for the
@ManyToOne
annotation is defaulted to
EAGER
. To under-
stand why this makes sense, it's helpful to understand how the
EntityManager
imple-
ments eager fetching. In effect, each eagerly fetched relationship turns into an addition-
al
JOIN
tacked onto the basic
SELECT
statement to retrieve the entity. To see what this
means, see how the
SELECT
statement for an eagerly fetched
Seller
record related to an
Item
looks in the following listing.
Listing 10.6.
SELECT
statement for eagerly fetched
Seller
related to an
Item
