Database object retrieval
As in Figure 944, “Retrieving hibintro.v1.model.User
instances by HQL. ” objects being
stored by Figure 951, “Inserting payment information ” may be queried using
HQL.
| Java | package inherit.v1;
...
public class RetrieveCredit {
public static void main(String[] args) {
...
final Transaction transaction = session.beginTransaction();
final Query searchCreditPayments = session.createQuery("from inherit.v1.CreditCard"); ❶
final List<CreditCard> creditCardList = (List<CreditCard>) searchCreditPayments.list();
for (final CreditCard c: creditCardList) {
System.out.println(c);
} ... |
| Sql | INFO: HHH000232: Schema update complete
Hibernate:
select
creditcard0_.id as id0_,
creditcard0_.created as created0_,
creditcard0_.number as number0_,
creditcard0_.cardType as cardType0_,
creditcard0_.expiration as expiration0_
from
BillingDetails creditcard0_
where
creditcard0_.dataType ❶='Credit card'
CreditCard: number=4412 8334 4512 9416, created 2013-02-19 13:09:22.0,
cardType=1, expiration=2015-05-18 00:00:00. ❷ |
Some Remarks: Our query asks for instances of
inherit.v2.CreditCard ❶. This gets implemented as an SQL SELECT choosing datasets whose
discriminator attribute value of dataType ❶ equals “Credit
card”. The current result set contains just one
element ❷ in accordance
with Figure 951, “Inserting payment information ”.
Retrieving both inherit.v1.CreditCard
and inherit.v1.BankAccount instances is
accomplished by querying for the common base class
inherit.v1.BillingDetails:
| Java | package inherit.v1;
...
public class RetrieveAll {
...
final Query searchBilling = session.createQuery("from inherit.v1.BillingDetails");
@SuppressWarnings("unchecked")
final List<BillingDetails> billingDetailsList = (List<BillingDetails>) searchBilling.list();
for (final BillingDetails c: billingDetailsList) {
System.out.println(c);
} ... |
| Sql | INFO: HHH000232: Schema update complete
Hibernate:
select
billingdet0_.id as id0_,
...
billingdet0_.dataType as dataType0_
from
BillingDetails billingdet0_
CreditCard: number=4412 8334 4512 9416, created 2013-02-19 13:09:22.0, ❶
cardType=1, expiration=2015-05-18 00:00:00.0
BankAccount: number=1107 2 31, created 2013-02-19 13:09:22.0,
bankName=Lehman Brothers, swiftcode=BARCGB22 |
This is the first example of a polymorphic query yielding a heterogeneous result set❶.
