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introduce incubating ProjectionSpecification API
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‎documentation/src/main/asciidoc/userguide/chapters/tooling/modelgen.adoc‎

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@@ -40,8 +40,8 @@ a static metamodel class based on the following rules:
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* The name of the metamodel class is derived from the name of the managed class by appending "_" to the managed class name.
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* The metamodel class `X_` must be annotated with the `jakarta.persistence.StaticMetamodel` annotation. The generation
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can also be configured to add the `javax.annotation.processing.Generated` annotation.
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* If class `X` extends another class `S`, where `S` is the most derived managed class extended by `X`, then
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class `X_` must extend class `S_`, where `S_` is the metamodel class created for `S`.
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* If class `X` extends another class `T`, where `T` is the most derived managed class extended by `X`, then
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class `X_` must extend class `S_`, where `S_` is the metamodel class created for `T`.
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* For every persistent singular attribute `y` declared by class `X`, where the type of `y` is `Y`,
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the metamodel class must contain a declaration as follows:
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@@ -69,7 +69,7 @@ class must contain a declaration as follows:
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where `K` is the type of the key of the map in class `X`
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* Import statements must be included for `jakarta.persistence.metamodel` types as
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needed, as well as all domain model classes (i.e., `X`, `S`, `Y`, `Z`, and `K`).
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needed, as well as all domain model classes (i.e., `X`, `T`, `Y`, `Z`, and `K`).
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As an example, consider the following domain model -
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‎hibernate-core/src/main/java/org/hibernate/query/specification/ProjectionSpecification.java‎

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/*
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* SPDX-License-Identifier: Apache-2.0
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* Copyright Red Hat Inc. and Hibernate Authors
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*/
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package org.hibernate.query.specification;
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import jakarta.persistence.EntityManager;
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import jakarta.persistence.TypedQueryReference;
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import jakarta.persistence.criteria.CriteriaBuilder;
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import jakarta.persistence.criteria.CriteriaQuery;
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import jakarta.persistence.metamodel.SingularAttribute;
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import org.hibernate.Incubating;
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import org.hibernate.Session;
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import org.hibernate.StatelessSession;
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import org.hibernate.query.SelectionQuery;
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import org.hibernate.query.restriction.Path;
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import org.hibernate.query.specification.internal.ProjectionSpecificationImpl;
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import java.util.function.Function;
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/**
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* Allows a {@link SelectionSpecification} to be augmented with the specification
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* of a projection list.
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* <pre>
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* var specification =
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* SelectionSpecification.create(Book.class)
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* .restrict(Restriction.contains(Book_.title, "hibernate", false))
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* .sort(Order.desc(Book_.title));
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* var projection = ProjectionSpecification.create( specification );
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* var bookIsbn = projection.select(Book_.isbn);
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* var bookTitle = projection.select(Book_.title);
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* var results = projection.createQuery(session).getResultList();
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* for (var result : results) {
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* var isbn = bookIsbn.in(result);
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* var title = bookTitle.in(result);
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* ...
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* }
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* </pre>
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* <p>
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* A {@code ProjectionSpecification} always results in a query which with result
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* type {@code Object[]}. The {@link #select(SingularAttribute) select()} methods
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* return {@link Element}, allowing easy and typesafe access to the elements of
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* the returned array.
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*
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* @param <T> The result type of the {@link SelectionSpecification}
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*
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* @since 7.2
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*
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* @author Gavin King
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*/
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@Incubating
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public interface ProjectionSpecification<T> extends QuerySpecification<Object[]> {
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/**
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* Create a new {@code ProjectionSpecification} which augments the given
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* {@link SelectionSpecification}.
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*/
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static <T> ProjectionSpecification<T> create(SelectionSpecification<T> selectionSpecification) {
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return new ProjectionSpecificationImpl<>( selectionSpecification );
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}
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/**
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* Allows typesafe access to elements of the {@code Object[]}
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* arrays returned by the query.
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*
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* @param <X> The type of the element of the projection list
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*/
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@FunctionalInterface
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interface Element<X> extends Function<Object[],X> {
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X in(Object[] tuple);
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@Override
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default X apply(Object[] tuple) {
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return in(tuple);
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}
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}
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/**
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* Select the given attribute of the root entity.
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*
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* @param attribute An attribute of the root entity
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* @return An {@link Element} allowing typesafe access to the results
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*/
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<X> Element<X> select(SingularAttribute<T,X> attribute);
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/**
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* Select the given field or property identified by the given path
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* from of the root entity.
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*
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* @param path A path from the root entity
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* @return An {@link Element} allowing typesafe access to the results
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*/
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<X> Element<X> select(Path<T,X> path);
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@Override
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SelectionQuery<Object[]> createQuery(Session session);
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@Override
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SelectionQuery<Object[]> createQuery(StatelessSession session);
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@Override
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SelectionQuery<Object[]> createQuery(EntityManager entityManager);
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@Override
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CriteriaQuery<Object[]> buildCriteria(CriteriaBuilder builder);
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@Override
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TypedQueryReference<Object[]> reference();
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@Override
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ProjectionSpecification<T> validate(CriteriaBuilder builder);
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}

‎hibernate-core/src/main/java/org/hibernate/query/specification/internal/ProjectionSpecificationImpl.java‎

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/*
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* SPDX-License-Identifier: Apache-2.0
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* Copyright Red Hat Inc. and Hibernate Authors
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*/
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package org.hibernate.query.specification.internal;
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import jakarta.persistence.EntityManager;
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import jakarta.persistence.TypedQueryReference;
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import jakarta.persistence.criteria.CriteriaBuilder;
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import jakarta.persistence.criteria.CriteriaQuery;
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import jakarta.persistence.metamodel.SingularAttribute;
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import org.hibernate.Session;
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import org.hibernate.SharedSessionContract;
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import org.hibernate.StatelessSession;
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import org.hibernate.query.SelectionQuery;
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import org.hibernate.query.restriction.Path;
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import org.hibernate.query.restriction.Restriction;
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import org.hibernate.query.specification.ProjectionSpecification;
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import org.hibernate.query.specification.QuerySpecification;
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import org.hibernate.query.specification.SelectionSpecification;
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import org.hibernate.query.sqm.NodeBuilder;
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import org.hibernate.query.sqm.tree.domain.SqmPath;
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import org.hibernate.query.sqm.tree.from.SqmRoot;
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import org.hibernate.query.sqm.tree.select.SqmSelectStatement;
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import org.hibernate.query.sqm.tree.select.SqmSelectableNode;
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import org.hibernate.query.sqm.tree.select.SqmSelection;
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import java.util.ArrayList;
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import java.util.Collections;
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import java.util.List;
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import java.util.Map;
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import java.util.function.BiFunction;
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/**
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* @author Gavin King
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*/
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public class ProjectionSpecificationImpl<T> implements ProjectionSpecification<T>, TypedQueryReference<Object[]> {
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private final SelectionSpecification<T> selectionSpecification;
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private final List<BiFunction<SqmSelectStatement<Object[]>, SqmRoot<T>, SqmSelectableNode<?>>> specifications = new ArrayList<>();
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public ProjectionSpecificationImpl(SelectionSpecification<T> selectionSpecification) {
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this.selectionSpecification = selectionSpecification;
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}
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@Override
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public <X> Element<X> select(SingularAttribute<T, X> attribute) {
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final int position = specifications.size();
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specifications.add( (select, root) -> root.get( attribute ) );
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return tuple -> (X) tuple[position];
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}
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@Override
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public <X> Element<X> select(Path<T, X> path) {
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final int position = specifications.size();
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specifications.add( (select, root) -> (SqmPath<X>) path.path( root ) );
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return tuple -> (X) tuple[position];
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}
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@Override
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public QuerySpecification<Object[]> restrict(Restriction<? super Object[]> restriction) {
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throw new UnsupportedOperationException( "This is not supported yet!" );
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}
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@Override
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public SelectionQuery<Object[]> createQuery(Session session) {
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return session.createSelectionQuery( buildCriteria( session.getCriteriaBuilder() ) );
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}
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@Override
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public SelectionQuery<Object[]> createQuery(StatelessSession session) {
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return session.createSelectionQuery( buildCriteria( session.getCriteriaBuilder() ) );
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}
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@Override
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public SelectionQuery<Object[]> createQuery(EntityManager entityManager) {
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return entityManager.unwrap( SharedSessionContract.class )
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.createQuery( buildCriteria( entityManager.getCriteriaBuilder() ) );
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}
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@Override
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public CriteriaQuery<Object[]> buildCriteria(CriteriaBuilder builder) {
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var impl = (SelectionSpecificationImpl<T>) selectionSpecification;
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// TODO: handle HQL, existing criteria
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final var tupleQuery =
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(SqmSelectStatement<Object[]>)
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builder.createQuery(Object[].class);
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final var root = tupleQuery.from( impl.getResultType() );
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// This cast is completely bogus
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final var castStatement = (SqmSelectStatement<T>) tupleQuery;
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impl.getSpecifications().forEach( spec -> spec.accept( castStatement, root ) );
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final var nodeBuilder = (NodeBuilder) builder;
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final var selectClause = tupleQuery.getQuerySpec().getSelectClause();
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for ( int i = 0; i < specifications.size(); i++ ) {
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final var selection = specifications.get( i ).apply( tupleQuery, root );
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selectClause.addSelection( new SqmSelection<>( selection, selection.getAlias(), nodeBuilder ) );
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}
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return tupleQuery;
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}
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@Override
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public ProjectionSpecification<T> validate(CriteriaBuilder builder) {
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selectionSpecification.validate( builder );
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// TODO: validate projection
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return this;
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}
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@Override
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public TypedQueryReference<Object[]> reference() {
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return this;
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}
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@Override
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public String getName() {
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return null;
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}
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@Override
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public Class<? extends Object[]> getResultType() {
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return Object[].class;
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}
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@Override
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public Map<String, Object> getHints() {
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return Collections.emptyMap();
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}
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}

‎hibernate-core/src/main/java/org/hibernate/query/specification/internal/SelectionSpecificationImpl.java‎

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@@ -96,6 +96,10 @@ public TypedQueryReference<T> reference() {
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return this;
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}
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public List<BiConsumer<SqmSelectStatement<T>, SqmRoot<T>>> getSpecifications() {
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return specifications;
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}
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@Override
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public SelectionSpecification<T> restrict(Restriction<? super T> restriction) {
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specifications.add( (sqmStatement, root) -> {

‎hibernate-core/src/test/java/org/hibernate/orm/test/query/dynamic/ProjectionSpecificationTest.java‎

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/*
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* SPDX-License-Identifier: Apache-2.0
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* Copyright Red Hat Inc. and Hibernate Authors
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*/
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package org.hibernate.orm.test.query.dynamic;
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import org.hibernate.query.restriction.Path;
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import org.hibernate.query.specification.ProjectionSpecification;
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import org.hibernate.query.specification.SelectionSpecification;
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import org.hibernate.testing.orm.junit.DomainModel;
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import org.hibernate.testing.orm.junit.SessionFactoryScope;
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import org.junit.jupiter.api.BeforeAll;
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import org.junit.jupiter.api.Test;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertNull;
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/**
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* @author Steve Ebersole
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*/
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@SuppressWarnings("JUnitMalformedDeclaration")
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@DomainModel(annotatedClasses = {BasicEntity.class, OtherEntity.class})
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@org.hibernate.testing.orm.junit.SessionFactory(useCollectingStatementInspector = true)
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public class ProjectionSpecificationTest {
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@BeforeAll
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public static void setup(SessionFactoryScope factoryScope) {
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factoryScope.inTransaction( (session) -> {
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session.createMutationQuery( "insert BasicEntity (id, name, position) values (1, 'Gavin', 2)" )
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.executeUpdate();
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} );
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}
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@Test
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void testProjection(SessionFactoryScope factoryScope) {
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factoryScope.inTransaction( (session) -> {
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var spec = SelectionSpecification.create( BasicEntity.class );
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var projection = ProjectionSpecification.create( spec );
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var position = projection.select( BasicEntity_.position );
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var name = projection.select( BasicEntity_.name );
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var id = projection.select( Path.from( BasicEntity.class ).to( BasicEntity_.id ) );
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var otherId = projection.select( Path.from( BasicEntity.class ).to( BasicEntity_.other ).to( OtherEntity_.id ) );
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var tuple = projection.createQuery( session ).getSingleResult();
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assertEquals( 2, position.in(tuple) );
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assertEquals( "Gavin", name.in(tuple) );
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assertEquals( 1, id.in(tuple) );
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assertNull( otherId.in( tuple ) );
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});
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}
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}

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