HHH-19364 add support for fetching single-valued paths

Author: gavinking

hibernate-core/src/main/java/org/hibernate/query/programmatic/SelectionSpecification.java

@@ -13,6 +13,7 @@
 import org.hibernate.query.Order;
 import org.hibernate.query.SelectionQuery;
 import org.hibernate.query.programmatic.internal.SelectionSpecificationImpl;
+import org.hibernate.query.restriction.Path;
 import org.hibernate.query.restriction.Restriction;
 
 import java.util.List;
@@ -91,6 +92,15 @@ public interface SelectionSpecification<T> extends QuerySpecification<T> {
 	@Override
 	SelectionSpecification<T> addRestriction(Restriction<T> restriction);
 
+	/**
+	 * Add a fetch {@linkplain Path path} to the specification.
+	 *
+	 * @param fetchPath The path to fetch
+	 *
+	 * @return {@code this} for method chaining.
+	 */
+	SelectionSpecification<T> addFetching(Path<T,?> fetchPath);
+
 	@FunctionalInterface
 	interface Mutator<T> {
 		void mutate(CriteriaBuilder builder, CriteriaQuery<T> query, Root<T> root);

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

@@ -12,6 +12,7 @@
 import org.hibernate.query.Order;
 import org.hibernate.query.SelectionQuery;
 import org.hibernate.query.programmatic.SelectionSpecification;
+import org.hibernate.query.restriction.Path;
 import org.hibernate.query.restriction.Restriction;
 import org.hibernate.query.spi.HqlInterpretation;
 import org.hibernate.query.spi.QueryEngine;
@@ -78,6 +79,12 @@ public SelectionSpecification<T> mutate(Mutator<T> mutation) {
 		return this;
 	}
 
+	@Override
+	public SelectionSpecification<T> addFetching(Path<T, ?> fetchPath) {
+		specifications.add( (sqmStatement, root) -> fetchPath.fetch( root ) );
+		return this;
+	}
+
 	@Override
 	public SelectionSpecification<T> addOrdering(Order<T> order) {
 		specifications.add( (sqmStatement, root) -> {

hibernate-core/src/main/java/org/hibernate/query/restriction/NamedPathElement.java

@@ -5,6 +5,8 @@
 package org.hibernate.query.restriction;
 
 import jakarta.persistence.criteria.Root;
+import jakarta.persistence.criteria.FetchParent;
+
 
 /**
  * A non-root element of a {@link Path}, using a stringly-typed
@@ -28,4 +30,9 @@ public jakarta.persistence.criteria.Path<V> path(Root<? extends X> root) {
 		}
 		return path;
 	}
+
+	@Override
+	public FetchParent<?, ? extends V> fetch(Root<? extends X> root) {
+		return parent.fetch( root ).fetch( attributeName );
+	}
 }

hibernate-core/src/main/java/org/hibernate/query/restriction/Path.java

@@ -5,6 +5,7 @@
 package org.hibernate.query.restriction;
 
 import jakarta.persistence.criteria.Root;
+import jakarta.persistence.criteria.FetchParent;
 import jakarta.persistence.metamodel.SingularAttribute;
 import org.hibernate.Incubating;
 import org.hibernate.query.range.Range;
@@ -76,4 +77,6 @@ default Restriction<X> notIn(List<U> values) {
 	default Restriction<X> notNull() {
 		return restrict( Range.notNull( getType() ) );
 	}
+
+	FetchParent<?, ? extends U> fetch(Root<? extends X> root);
 }

hibernate-core/src/main/java/org/hibernate/query/restriction/PathElement.java

@@ -5,6 +5,7 @@
 package org.hibernate.query.restriction;
 
 import jakarta.persistence.criteria.Root;
+import jakarta.persistence.criteria.FetchParent;
 import jakarta.persistence.metamodel.SingularAttribute;
 
 /**
@@ -23,4 +24,9 @@ public Class<V> getType() {
 	public jakarta.persistence.criteria.Path<V> path(Root<? extends X> root) {
 		return parent.path( root ).get( attribute );
 	}
+
+	@Override
+	public FetchParent<?, ? extends V> fetch(Root<? extends X> root) {
+		return parent.fetch( root ).fetch( attribute );
+	}
 }

hibernate-core/src/main/java/org/hibernate/query/restriction/PathRoot.java

@@ -5,6 +5,7 @@
 package org.hibernate.query.restriction;
 
 import jakarta.persistence.criteria.Root;
+import jakarta.persistence.criteria.FetchParent;
 
 /**
  * A root element of a {@link Path}.
@@ -23,4 +24,9 @@ public jakarta.persistence.criteria.Path<X> path(Root<? extends X> root) {
 		// unchecked cast only to get rid of the upper bound
 		return (jakarta.persistence.criteria.Path<X>) root;
 	}
+
+	@Override
+	public FetchParent<?, ? extends X> fetch(Root<? extends X> root) {
+		return root;
+	}
 }

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

@@ -6,6 +6,7 @@
 
 import jakarta.persistence.Entity;
 import jakarta.persistence.Id;
+import jakarta.persistence.ManyToOne;
 import jakarta.persistence.Table;
 
 /**
@@ -18,4 +19,7 @@ public class BasicEntity {
 	private Integer id;
 	private String name;
 	private int position;
+
+	@ManyToOne
+	OtherEntity other;
 }

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

@@ -0,0 +1,16 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.orm.test.query.dynamic;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import jakarta.persistence.Table;
+
+@Entity(name = "OtherEntity")
+@Table(name = "OtherEntity")
+public class OtherEntity {
+	@Id
+	private Integer id;
+}

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

@@ -11,6 +11,7 @@
 import org.hibernate.query.programmatic.MutationSpecification;
 import org.hibernate.query.programmatic.SelectionSpecification;
 import org.hibernate.query.range.Range;
+import org.hibernate.query.restriction.Path;
 import org.hibernate.query.restriction.Restriction;
 import org.hibernate.testing.jdbc.SQLStatementInspector;
 import org.hibernate.testing.orm.junit.DomainModel;
@@ -26,7 +27,7 @@
  * @author Steve Ebersole
  */
 @SuppressWarnings("JUnitMalformedDeclaration")
-@DomainModel(annotatedClasses = BasicEntity.class)
+@DomainModel(annotatedClasses = {BasicEntity.class, OtherEntity.class})
 @org.hibernate.testing.orm.junit.SessionFactory(useCollectingStatementInspector = true)
 public class SimpleQuerySpecificationTests {
 	@Test
@@ -184,6 +185,7 @@ void testCriteriaForm(SessionFactoryScope factoryScope) {
 			query.where( criteriaBuilder.like( entity.get( BasicEntity_.name ), "%" ) );
 			SelectionSpecification.create( query )
 					.addOrdering( Order.asc( BasicEntity_.position ) )
+					.addFetching( Path.from(BasicEntity.class).to( BasicEntity_.other ) )
 					.createQuery( session )
 					.getResultList();
 		} );