prototype for Assignments and ProjectionSpecifications

hibernate-core/src/main/java/org/hibernate/proxy/pojo/BasicLazyInitializer.java

@@ -86,7 +86,6 @@ else if ( method.equals( setIdentifierMethod ) ) {
 
 		// otherwise:
 		return INVOKE_IMPLEMENTATION;
-
 	}
 
 	private Object getReplacement() {

hibernate-core/src/main/java/org/hibernate/query/assignment/Assignment.java

@@ -0,0 +1,60 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.query.assignment;
+
+
+import jakarta.persistence.metamodel.SingularAttribute;
+import org.hibernate.Incubating;
+import org.hibernate.query.restriction.Path;
+import org.hibernate.query.sqm.tree.update.SqmUpdateStatement;
+
+/**
+ * An assignment to a field or property of an entity or embeddable.
+ *
+ * @param <T> The target entity type of the assignment
+ *
+ * @since 7.2
+ *
+ * @author Gavin King
+ */
+@Incubating
+public interface Assignment<T> {
+
+	/**
+	 * An assigment of the given literal value to the given attribute
+	 * of the root entity.
+	 */
+	static <T,X> Assignment<T> set(SingularAttribute<T,X> attribute, X value) {
+		return new AttributeAssignment<>( attribute, value );
+	}
+
+	/**
+	 * An assigment of the given literal value to the entity or embeddable
+	 * field or property identified by the given path from the root entity.
+	 */
+	static <T,X> Assignment<T> set(Path<T,X> path, X value) {
+		return new PathAssignment<>( path, value );
+	}
+
+	/**
+	 * An assigment of the entity or embeddable field or property identified
+	 * by the given path from the root entity to the given attribute of the
+	 * root entity.
+	 */
+	static <T,X> Assignment<T> set(SingularAttribute<T,X> attribute, Path<T,X> value) {
+		return new PathToAttributeAssignment<>( attribute, value );
+	}
+
+	/**
+	 * An assigment of one entity or embeddable field or property to another
+	 * entity or embeddable field or property, each identified by a given path
+	 * from the root entity.
+	 */
+	static <T,X> Assignment<T> set(Path<T,X> path, Path<T,X> value) {
+		return new PathToPathAssignment<>( path, value );
+	}
+
+	void apply(SqmUpdateStatement<? extends T> update);
+}

hibernate-core/src/main/java/org/hibernate/query/assignment/AttributeAssignment.java

@@ -0,0 +1,21 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.query.assignment;
+
+import jakarta.persistence.metamodel.SingularAttribute;
+import org.hibernate.query.sqm.tree.update.SqmUpdateStatement;
+
+/**
+ * Assignment of a value to an attribute.
+ *
+ * @author Gavin King
+ */
+record AttributeAssignment<T, X>(SingularAttribute<T, X> attribute, X value)
+		implements Assignment<T> {
+	@Override
+	public void apply(SqmUpdateStatement<? extends T> update) {
+		update.set( attribute, value );
+	}
+}

hibernate-core/src/main/java/org/hibernate/query/assignment/PathAssignment.java

@@ -0,0 +1,21 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.query.assignment;
+
+import org.hibernate.query.restriction.Path;
+import org.hibernate.query.sqm.tree.update.SqmUpdateStatement;
+
+/**
+ * Assignment of a value to a path.
+ *
+ * @author Gavin King
+ */
+record PathAssignment<T, X>(Path<T, X> path, X value)
+		implements Assignment<T> {
+	@Override
+	public void apply(SqmUpdateStatement<? extends T> update) {
+		update.set( path.path( update.getRoot() ), value );
+	}
+}

hibernate-core/src/main/java/org/hibernate/query/assignment/PathToAttributeAssignment.java

@@ -0,0 +1,22 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.query.assignment;
+
+import jakarta.persistence.metamodel.SingularAttribute;
+import org.hibernate.query.restriction.Path;
+import org.hibernate.query.sqm.tree.update.SqmUpdateStatement;
+
+/**
+ * Assignment of a path to an attribute.
+ *
+ * @author Gavin King
+ */
+record PathToAttributeAssignment<T, X>(SingularAttribute<T, X> attribute, Path<T,X> value)
+		implements Assignment<T> {
+	@Override
+	public void apply(SqmUpdateStatement<? extends T> update) {
+		update.set( attribute, value.path( update.getRoot() ) );
+	}
+}

hibernate-core/src/main/java/org/hibernate/query/assignment/PathToPathAssignment.java

@@ -0,0 +1,21 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.query.assignment;
+
+import org.hibernate.query.restriction.Path;
+import org.hibernate.query.sqm.tree.update.SqmUpdateStatement;
+
+/**
+ *  * Assignment of a path to a path.
+ *
+ * @author Gavin King
+ */
+record PathToPathAssignment<T, X>(Path<T, X> path, Path<T,X> value)
+		implements Assignment<T> {
+	@Override
+	public void apply(SqmUpdateStatement<? extends T> update) {
+		update.set( path.path( update.getRoot() ), value.path( update.getRoot() ) );
+	}
+}

hibernate-core/src/main/java/org/hibernate/query/assignment/package-info.java

@@ -0,0 +1,10 @@
+/**
+ * Support for {@linkplain org.hibernate.query.assignment.Assignment assignment}
+ * with {@link org.hibernate.query.specification.MutationSpecification}.
+ *
+ * @since 7.2
+ */
+@Incubating
+package org.hibernate.query.assignment;
+
+import org.hibernate.Incubating;

hibernate-core/src/main/java/org/hibernate/query/specification/DeleteSpecification.java

@@ -0,0 +1,61 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.query.specification;
+
+import jakarta.persistence.criteria.CriteriaBuilder;
+import jakarta.persistence.criteria.CriteriaDelete;
+import org.hibernate.Incubating;
+import org.hibernate.query.restriction.Restriction;
+import org.hibernate.query.specification.internal.DeleteSpecificationImpl;
+
+/**
+ * Specialization of {@link MutationSpecification} for programmatic customization
+ * of delete queries.
+ * <p>
+ *
+ * @param <T> The entity type which is the target of the mutation.
+ *
+ * @author Gavin King
+ *
+ * @since 7.2
+ */
+@Incubating
+public interface DeleteSpecification<T> extends MutationSpecification<T> {
+	@Override
+	DeleteSpecification<T> restrict(Restriction<? super T> restriction);
+
+	@Override
+	DeleteSpecification<T> augment(Augmentation<T> augmentation);
+
+	@Override
+	DeleteSpecification<T> validate(CriteriaBuilder builder);
+
+	/**
+	 * Returns a specification reference which can be used to programmatically,
+	 * iteratively build a {@linkplain org.hibernate.query.MutationQuery} which
+	 * deletes the given entity type.
+	 *
+	 * @param targetEntityClass The target entity type
+	 *
+	 * @param <T> The root entity type for the mutation (the "target").
+	 */
+	static <T> DeleteSpecification<T> create(Class<T> targetEntityClass) {
+		return new DeleteSpecificationImpl<>( targetEntityClass );
+	}
+
+	/**
+	 * Returns a specification reference which can be used to programmatically,
+	 * iteratively build a {@linkplain org.hibernate.query.MutationQuery} based
+	 * on the given criteria delete, allowing the addition of
+	 * {@linkplain #restrict restrictions}.
+	 *
+	 * @param criteriaDelete The criteria delete query
+	 *
+	 * @param <T> The root entity type for the mutation (the "target").
+	 */
+	static <T> DeleteSpecification<T> create(CriteriaDelete<T> criteriaDelete) {
+		return new DeleteSpecificationImpl<>( criteriaDelete );
+	}
+}

hibernate-core/src/main/java/org/hibernate/query/specification/MutationSpecification.java

@@ -114,6 +114,8 @@ static <T> MutationSpecification<T> create(Class<T> mutationTarget, String hql)
 	 * @param criteriaUpdate The criteria update query
 	 *
 	 * @param <T> The root entity type for the mutation (the "target").
+	 *
+	 * @see UpdateSpecification#create(CriteriaUpdate)
 	 */
 	static <T> MutationSpecification<T> create(CriteriaUpdate<T> criteriaUpdate) {
 		return new MutationSpecificationImpl<>( criteriaUpdate );
@@ -127,6 +129,8 @@ static <T> MutationSpecification<T> create(CriteriaUpdate<T> criteriaUpdate) {
 	 * @param criteriaDelete The criteria delete query
 	 *
 	 * @param <T> The root entity type for the mutation (the "target").
+	 *
+	 * @see DeleteSpecification#create(CriteriaDelete)
 	 */
 	static <T> MutationSpecification<T> create(CriteriaDelete<T> criteriaDelete) {
 		return new MutationSpecificationImpl<>( criteriaDelete );

hibernate-core/src/main/java/org/hibernate/query/specification/ProjectionSpecification.java

@@ -0,0 +1,115 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.query.specification;
+
+import jakarta.persistence.EntityManager;
+import jakarta.persistence.TypedQueryReference;
+import jakarta.persistence.criteria.CriteriaBuilder;
+import jakarta.persistence.criteria.CriteriaQuery;
+import jakarta.persistence.metamodel.SingularAttribute;
+import org.hibernate.Incubating;
+import org.hibernate.Session;
+import org.hibernate.StatelessSession;
+import org.hibernate.query.SelectionQuery;
+import org.hibernate.query.restriction.Path;
+import org.hibernate.query.specification.internal.ProjectionSpecificationImpl;
+
+import java.util.function.Function;
+
+/**
+ * Allows a {@link SelectionSpecification} to be augmented with the specification
+ * of a projection list.
+ * <pre>
+ * var specification =
+ *         SelectionSpecification.create(Book.class)
+ *                 .restrict(Restriction.contains(Book_.title, "hibernate", false))
+ *                 .sort(Order.desc(Book_.title));
+ * var projection = ProjectionSpecification.create(specification);
+ * var bookIsbn = projection.select(Book_.isbn);
+ * var bookTitle = projection.select(Book_.title);
+ * var results = projection.createQuery(session).getResultList();
+ * for (var result : results) {
+ *     var isbn = bookIsbn.in(result);
+ *     var title = bookTitle.in(result);
+ *     ...
+ * }
+ * </pre>
+ * <p>
+ * A {@code ProjectionSpecification} always results in a query which with result
+ * type {@code Object[]}. The {@link #select(SingularAttribute) select()} methods
+ * return {@link Element}, allowing easy and typesafe access to the elements of
+ * the returned array.
+ *
+ * @param <T> The result type of the {@link SelectionSpecification}
+ *
+ * @since 7.2
+ *
+ * @apiNote This interface marked {@link Incubating} is considered experimental.
+ *          Changes to the API defined here are fully expected in future releases.
+ *
+ * @author Gavin King
+ */
+@Incubating
+public interface ProjectionSpecification<T> extends QuerySpecification<Object[]> {
+
+	/**
+	 * Create a new {@code ProjectionSpecification} which augments the given
+	 * {@link SelectionSpecification}.
+	 */
+	static <T> ProjectionSpecification<T> create(SelectionSpecification<T> selectionSpecification) {
+		return new ProjectionSpecificationImpl<>( selectionSpecification );
+	}
+
+	/**
+	 * Allows typesafe access to elements of the {@code Object[]}
+	 * arrays returned by the query.
+	 *
+	 * @param <X> The type of the element of the projection list
+	 */
+	@FunctionalInterface
+	interface Element<X> extends Function<Object[],X> {
+		X in(Object[] tuple);
+
+		@Override
+		default X apply(Object[] tuple) {
+			return in(tuple);
+		}
+	}
+
+	/**
+	 * Select the given attribute of the root entity.
+	 *
+	 * @param attribute An attribute of the root entity
+	 * @return An {@link Element} allowing typesafe access to the results
+	 */
+	<X> Element<X> select(SingularAttribute<T,X> attribute);
+
+	/**
+	 * Select the given field or property identified by the given path
+	 * from of the root entity.
+	 *
+	 * @param path A path from the root entity
+	 * @return An {@link Element} allowing typesafe access to the results
+	 */
+	<X> Element<X> select(Path<T,X> path);
+
+		@Override
+	SelectionQuery<Object[]> createQuery(Session session);
+
+	@Override
+	SelectionQuery<Object[]> createQuery(StatelessSession session);
+
+	@Override
+	SelectionQuery<Object[]> createQuery(EntityManager entityManager);
+
+	@Override
+	CriteriaQuery<Object[]> buildCriteria(CriteriaBuilder builder);
+
+	@Override
+	TypedQueryReference<Object[]> reference();
+
+	@Override
+	ProjectionSpecification<T> validate(CriteriaBuilder builder);
+}