HHH-15105 Test and fix for NPE when access default query cache region statistics

hibernate-core/src/main/java/org/hibernate/cache/internal/EnabledCaching.java

@@ -523,6 +523,10 @@ public class EnabledCaching implements CacheImplementor, DomainDataRegionBuildin
 			return null;
 		}
 
+		if ( regionName == null || regionName.equals( getDefaultQueryResultsCache().getRegion().getName() ) ) {
+			return getDefaultQueryResultsCache();
+		}
+
 		return namedQueryResultsCacheMap.get( regionName );
 	}
 

hibernate-core/src/test/java/org/hibernate/orm/test/cache/CacheRegionStatisticsTest.java

@@ -0,0 +1,114 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * 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.cache;
+
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import jakarta.persistence.ElementCollection;
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+
+import org.hibernate.boot.MetadataSources;
+import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
+import org.hibernate.cfg.AvailableSettings;
+import org.hibernate.stat.CacheRegionStatistics;
+import org.hibernate.stat.Statistics;
+
+import org.hibernate.testing.TestForIssue;
+import org.hibernate.testing.cache.CachingRegionFactory;
+import org.hibernate.testing.junit4.BaseNonConfigCoreFunctionalTestCase;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.hibernate.testing.transaction.TransactionUtil.doInHibernate;
+import static org.junit.Assert.assertEquals;
+
+/**
+ * @author Christian Beikov
+ */
+public class CacheRegionStatisticsTest extends BaseNonConfigCoreFunctionalTestCase {
+
+	@Test
+	@TestForIssue( jiraKey = "HHH-15105")
+	public void testAccessDefaultQueryRegionStatistics() {
+		final Statistics statistics = sessionFactory().getStatistics();
+		final CacheRegionStatistics queryRegionStatistics = statistics.getQueryRegionStatistics(
+				"default-query-results-region"
+		);
+		doInHibernate(
+				this::sessionFactory, session -> {
+					List<Dog> resultList = session.createQuery( "from Dog", Dog.class )
+							.setCacheable( true )
+							.getResultList();
+
+					assertEquals( 1, queryRegionStatistics.getMissCount() );
+				}
+		);
+	}
+
+	@Override
+	protected void configureStandardServiceRegistryBuilder(StandardServiceRegistryBuilder ssrb) {
+		super.configureStandardServiceRegistryBuilder( ssrb );
+		ssrb.applySetting( AvailableSettings.USE_SECOND_LEVEL_CACHE, true );
+		ssrb.applySetting( AvailableSettings.USE_QUERY_CACHE, true );
+		ssrb.applySetting( AvailableSettings.CACHE_REGION_FACTORY, new CachingRegionFactory() );
+		ssrb.applySetting( AvailableSettings.GENERATE_STATISTICS, "true" );
+	}
+
+	@Override
+	protected void applyMetadataSources(MetadataSources metadataSources) {
+		super.applyMetadataSources( metadataSources );
+		metadataSources.addAnnotatedClass( Dog.class );
+	}
+
+	@Before
+	public void setupData() {
+		doInHibernate(
+				this::sessionFactory, session -> {
+					Dog yogi = new Dog( "Yogi" );
+					yogi.nickNames.add( "The Yog" );
+					yogi.nickNames.add( "Little Boy" );
+					yogi.nickNames.add( "Yogaroni Macaroni" );
+					Dog irma = new Dog( "Irma" );
+					irma.nickNames.add( "Squirmy" );
+					irma.nickNames.add( "Bird" );
+					session.persist( yogi );
+					session.persist( irma );
+				}
+		);
+	}
+
+	@After
+	public void cleanupData() {
+		doInHibernate(
+				this::sessionFactory, session -> {
+					List<Dog> dogs = session.createQuery( "from Dog", Dog.class ).getResultList();
+					for ( Dog dog : dogs ) {
+						session.delete( dog );
+					}
+				}
+		);
+	}
+
+	@Entity(name = "Dog")
+	public static class Dog {
+		@Id
+		private String name;
+
+		@ElementCollection
+		private Set<String> nickNames = new HashSet<>();
+
+		public Dog(String name) {
+			this.name = name;
+		}
+
+		public Dog() {
+		}
+	}
+}