Hibernate
/
hibernate-orm
mirror of https://github.com/hibernate/hibernate-orm
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

HHH-17410 Add documentation for count query creation

This commit is contained in:
Christian Beikov 2023-11-10 13:01:37 +01:00
parent e9d08ca18e
commit ea2c360eba
3 changed files with 44 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
documentation/src/main/asciidoc/userguide/Hibernate_User_Guide.adoc
View File

@ -32,6 +32,7 @@ include::chapters/events/Events.adoc[]
include::chapters/query/hql/Query.adoc[]
include::chapters/query/hql/QueryLanguage.adoc[]
include::chapters/query/criteria/Criteria.adoc[]
include::chapters/query/criteria/CriteriaExtensions.adoc[]
include::chapters/query/native/Native.adoc[]
include::chapters/query/spatial/Spatial.adoc[]
include::chapters/query/extensions/Vector.adoc[]

34
documentation/src/main/asciidoc/userguide/chapters/query/criteria/CriteriaExtensions.adoc Normal file
View File

@ -0,0 +1,34 @@
[[criteria-extensions]]
== Criteria extensions
:root-project-dir: ../../../../../../../..
:core-project-dir: {root-project-dir}/hibernate-core
:example-dir-criteria: {core-project-dir}/src/test/java/org/hibernate/orm/test/query/criteria
Hibernate ORM provides extensions to the JPA Criteria API to allow making use of HQL features through the Criteria API.
The `Session` interface gives access to the `org.hibernate.query.criteria.HibernateCriteriaBuilder`,
a subtype of `jakarta.persistence.criteria.CriteriaBuilder`,
through the `Session#getCriteriaBuilder()` method, which is the entry point to the extensions.
The `HibernateCriteriaBuilder` interface offers additional methods, but also provides co-variant overridden methods,
which return subtypes of that the respective `jakarta.persistence.criteria.CriteriaBuilder` methods return types.
The subtypes are consistently named by prefixing `Jpa` i.e. `Expression` becomes `JpaExpression`.
These subtypes provide additional methods and co-variant overrides to ease working with the extensions.
[[criteria-extensions-count-query]]
=== Count query creation
A very common requirement is the creation of a count query based on an existing query.
This can be done by using the `JpaCriteriaQuery#createCountQuery()` method.
[[criteria-extensions-count-query-example]]
====
[source, JAVA, indent=0]
----
include::{example-dir-criteria}/CountQueryTests.java[tags=criteria-extensions-count-query-example]
----
====
The resulting count query will wrap a copy of the original query as subquery in the from clause and select `count(*)`.

17
hibernate-core/src/test/java/org/hibernate/orm/test/query/CountQueryTests.java → hibernate-core/src/test/java/org/hibernate/orm/test/query/criteria/CountQueryTests.java
View File

@ -4,7 +4,7 @@
* License: GNU Lesser General Public License (LGPL), version 2.1 or later
* See the lgpl.txt file in the root directory or http://www.gnu.org/licenses/lgpl-2.1.html
*/
package org.hibernate.orm.test.query;
package org.hibernate.orm.test.query.criteria;
import java.time.LocalDate;
import java.util.List;
@ -129,21 +129,22 @@ public class CountQueryTests {
public void testParameters(SessionFactoryScope scope) {
scope.inTransaction(
session -> {
//tag::criteria-extensions-count-query-example[]
final HibernateCriteriaBuilder cb = session.getCriteriaBuilder();
final JpaCriteriaQuery<Tuple> cq = cb.createTupleQuery();
final JpaRoot<Contact> root = cq.from( Contact.class );
cq.multiselect(
root.get( "id" ),
root.get( "name" )
);
final JpaParameterExpression<Contact.Gender> parameter = cb.parameter( Contact.Gender.class );
cq.multiselect( root.get( "id" ), root.get( "name" ) );
cq.where( root.get( "gender" ).equalTo( parameter ) );
final List<Tuple> resultList = session.createQuery( cq )
.setParameter( parameter, Contact.Gender.FEMALE )
.getResultList();
final Long count = session.createQuery( cq.createCountQuery() )
.setParameter( parameter, Contact.Gender.FEMALE )
.getSingleResult();
//end::criteria-extensions-count-query-example[]
final List<Tuple> resultList = session.createQuery( cq )
.setParameter( parameter, Contact.Gender.FEMALE )
.getResultList();
assertEquals( resultList.size(), count.intValue() );
}
);