HHH-7610 Add an option to initialize empty components when all the properties are null

Note that this commit also changes the semantic of the comparison between a null component
and a component with all properties null: they are considered equivalent.

hibernate-core/src/main/java/org/hibernate/cfg/AvailableSettings.java

@@ -1009,4 +1009,13 @@ public interface AvailableSettings {
 	 * Values are {@code true} (pass the NULLs) or {@code false} (do not pass the NULLs).
 	 */
 	String PROCEDURE_NULL_PARAM_PASSING = "hibernate.proc.param_null_passing";
+
+	/*
+	 * Enable instantiation of composite/embedded objects when all of its attribute values are {@code null}.
+	 * The default (and historical) behavior is that a {@code null} reference will be used to represent the 
+	 * composite when all of its attributes are {@code null}
+	 *
+	 * @since 5.1
+	 */
+	String CREATE_EMPTY_COMPOSITES_ENABLED = "hibernate.create_empty_composites.enabled";
 }

hibernate-core/src/main/java/org/hibernate/tuple/component/ComponentMetamodel.java

@@ -14,6 +14,9 @@ import java.util.Map;
 import org.hibernate.EntityMode;
 import org.hibernate.HibernateException;
 import org.hibernate.boot.spi.MetadataBuildingOptions;
+import org.hibernate.cfg.Environment;
+import org.hibernate.engine.config.spi.ConfigurationService;
+import org.hibernate.internal.util.config.ConfigurationHelper;
 import org.hibernate.mapping.Component;
 import org.hibernate.mapping.Property;
 import org.hibernate.tuple.PropertyFactory;
@@ -39,6 +42,7 @@ public class ComponentMetamodel implements Serializable {
 	// cached for efficiency...
 	private final int propertySpan;
 	private final Map propertyIndexes = new HashMap();
+	private final boolean createEmptyCompositesEnabled;
 
 //	public ComponentMetamodel(Component component, SessionFactoryImplementor sessionFactory) {
 	public ComponentMetamodel(Component component, MetadataBuildingOptions metadataBuildingOptions) {
@@ -65,6 +69,15 @@ public class ComponentMetamodel implements Serializable {
 				entityMode,
 				component
 		) : componentTuplizerFactory.constructTuplizer( tuplizerClassName, component );
+
+		final ConfigurationService cs = component.getMetadata().getMetadataBuildingOptions().getServiceRegistry()
+				.getService(ConfigurationService.class);
+
+		this.createEmptyCompositesEnabled = ConfigurationHelper.getBoolean(
+				Environment.CREATE_EMPTY_COMPOSITES_ENABLED,
+				cs.getSettings(),
+				false
+		);
 	}
 
 	public boolean isKey() {
@@ -106,4 +119,8 @@ public class ComponentMetamodel implements Serializable {
 		return componentTuplizer;
 	}
 
+	public boolean isCreateEmptyCompositesEnabled() {
+		return createEmptyCompositesEnabled;
+	}
+
 }

hibernate-core/src/main/java/org/hibernate/type/ComponentType.java

@@ -49,6 +49,7 @@ public class ComponentType extends AbstractType implements CompositeType, Proced
 	private final FetchMode[] joinedFetch;
 	private final boolean isKey;
 	private boolean hasNotNullProperty;
+	private final boolean createEmptyCompositesEnabled;
 
 	protected final EntityMode entityMode;
 	protected final ComponentTuplizer componentTuplizer;
@@ -80,6 +81,7 @@ public class ComponentType extends AbstractType implements CompositeType, Proced
 
 		this.entityMode = metamodel.getEntityMode();
 		this.componentTuplizer = metamodel.getComponentTuplizer();
+		this.createEmptyCompositesEnabled = metamodel.isCreateEmptyCompositesEnabled();
 	}
 
 	public boolean isKey() {
@@ -158,9 +160,7 @@ public class ComponentType extends AbstractType implements CompositeType, Proced
 		if ( x == y ) {
 			return true;
 		}
-		if ( x == null || y == null ) {
+		// null value and empty component are considered equivalent
-			return false;
-		}
 		Object[] xvalues = getPropertyValues( x, entityMode );
 		Object[] yvalues = getPropertyValues( y, entityMode );
 		for ( int i = 0; i < propertySpan; i++ ) {
@@ -176,9 +176,7 @@ public class ComponentType extends AbstractType implements CompositeType, Proced
 		if ( x == y ) {
 			return true;
 		}
-		if ( x == null || y == null ) {
+		// null value and empty component are considered equivalent
-			return false;
-		}
 		for ( int i = 0; i < propertySpan; i++ ) {
 			if ( !propertyTypes[i].isEqual( getPropertyValue( x, i ), getPropertyValue( y, i ) ) ) {
 				return false;
@@ -193,9 +191,7 @@ public class ComponentType extends AbstractType implements CompositeType, Proced
 		if ( x == y ) {
 			return true;
 		}
-		if ( x == null || y == null ) {
+		// null value and empty component are considered equivalent
-			return false;
-		}
 		for ( int i = 0; i < propertySpan; i++ ) {
 			if ( !propertyTypes[i].isEqual( getPropertyValue( x, i ), getPropertyValue( y, i ), factory ) ) {
 				return false;
@@ -253,9 +249,7 @@ public class ComponentType extends AbstractType implements CompositeType, Proced
 		if ( x == y ) {
 			return false;
 		}
-		if ( x == null || y == null ) {
+		// null value and empty component are considered equivalent
-			return true;
-		}
 		for ( int i = 0; i < propertySpan; i++ ) {
 			if ( propertyTypes[i].isDirty( getPropertyValue( x, i ), getPropertyValue( y, i ), session ) ) {
 				return true;
@@ -269,9 +263,7 @@ public class ComponentType extends AbstractType implements CompositeType, Proced
 		if ( x == y ) {
 			return false;
 		}
-		if ( x == null || y == null ) {
+		// null value and empty component are considered equivalent
-			return true;
-		}
 		int loc = 0;
 		for ( int i = 0; i < propertySpan; i++ ) {
 			int len = propertyTypes[i].getColumnSpan( session.getFactory() );
@@ -408,6 +400,9 @@ public class ComponentType extends AbstractType implements CompositeType, Proced
 
 	public Object getPropertyValue(Object component, int i)
 			throws HibernateException {
+		if (component == null) {
+			component = new Object[propertySpan];
+		}
 		if ( component instanceof Object[] ) {
 			// A few calls to hashCode pass the property values already in an
 			// Object[] (ex: QueryKey hash codes for cached queries).
@@ -429,6 +424,9 @@ public class ComponentType extends AbstractType implements CompositeType, Proced
 	@Override
 	public Object[] getPropertyValues(Object component, EntityMode entityMode)
 			throws HibernateException {
+		if (component == null) {
+			component = new Object[propertySpan];
+		}
 		if ( component instanceof Object[] ) {
 			// A few calls to hashCode pass the property values already in an 
 			// Object[] (ex: QueryKey hash codes for cached queries).
@@ -689,6 +687,9 @@ public class ComponentType extends AbstractType implements CompositeType, Proced
 			setPropertyValues( result, resolvedValues, entityMode );
 			return result;
 		}
+		else if ( isCreateEmptyCompositesEnabled() ) {
+			return instantiate( owner, session );
+		}
 		else {
 			return null;
 		}
@@ -827,4 +828,8 @@ public class ComponentType extends AbstractType implements CompositeType, Proced
 	public boolean hasNotNullProperty() {
 		return hasNotNullProperty;
 	}
+
+	private boolean isCreateEmptyCompositesEnabled() {
+		return createEmptyCompositesEnabled;
+	}
 }

hibernate-core/src/test/java/org/hibernate/test/component/empty/ComponentEmptyEmbedded.java

@@ -0,0 +1,34 @@
+/*
+ * 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.test.component.empty;
+
+import javax.persistence.Embeddable;
+
+@Embeddable
+public class ComponentEmptyEmbedded {
+
+	private String field1;
+
+	private String field2;
+
+	public String getField1() {
+		return field1;
+	}
+
+	public void setField1(String field1) {
+		this.field1 = field1;
+	}
+
+	public String getField2() {
+		return field2;
+	}
+
+	public void setField2(String field2) {
+		this.field2 = field2;
+	}
+
+}

hibernate-core/src/test/java/org/hibernate/test/component/empty/ComponentEmptyEmbeddedOwner.java

@@ -0,0 +1,38 @@
+/*
+ * 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.test.component.empty;
+
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.Id;
+
+@Entity
+public class ComponentEmptyEmbeddedOwner {
+
+	@Id
+	@GeneratedValue
+	private Integer id;
+
+	private ComponentEmptyEmbedded embedded;
+
+	public Integer getId() {
+		return id;
+	}
+
+	public void setId(Integer id) {
+		this.id = id;
+	}
+
+	public ComponentEmptyEmbedded getEmbedded() {
+		return embedded;
+	}
+
+	public void setEmbedded(ComponentEmptyEmbedded embedded) {
+		this.embedded = embedded;
+	}
+
+}

hibernate-core/src/test/java/org/hibernate/test/component/empty/EmptyCompositesDirtynessTest.java

@@ -0,0 +1,63 @@
+/*
+ * 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.test.component.empty;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+
+import org.hibernate.Session;
+import org.hibernate.cfg.Configuration;
+import org.hibernate.cfg.Environment;
+import org.hibernate.testing.TestForIssue;
+import org.hibernate.testing.junit4.BaseCoreFunctionalTestCase;
+import org.junit.Test;
+
+/**
+ * Test class for empty embedded dirtiness computation.
+ *
+ * @author Laurent Almeras
+ */
+public class EmptyCompositesDirtynessTest extends BaseCoreFunctionalTestCase {
+
+	@Override
+	protected Class<?>[] getAnnotatedClasses() {
+		return new Class[] { ComponentEmptyEmbeddedOwner.class, ComponentEmptyEmbedded.class };
+	}
+
+	@Override
+	protected void configure(Configuration configuration) {
+		super.configure( configuration );
+		configuration.getProperties().put( Environment.CREATE_EMPTY_COMPOSITES_ENABLED, Boolean.valueOf( false ) );
+	}
+
+	/**
+	 * Test for dirtyness computation consistency when a property is an empty composite.
+	 */
+	@Test
+	@TestForIssue(jiraKey = "HHH-7610")
+	public void testCompositesEmpty() {
+		Session s = openSession();
+		s.getTransaction().begin();
+
+		ComponentEmptyEmbeddedOwner owner = new ComponentEmptyEmbeddedOwner();
+		s.persist( owner );
+
+		s.flush();
+		s.getTransaction().commit();
+
+		s.clear();
+		s.getTransaction().begin();
+		owner = (ComponentEmptyEmbeddedOwner) s.get( ComponentEmptyEmbeddedOwner.class, owner.getId() );
+		assertNull( owner.getEmbedded() );
+		owner.setEmbedded( new ComponentEmptyEmbedded() );
+
+		// technically, as all properties are null, update may not be necessary
+		assertFalse( session.isDirty() ); // must be false to avoid unnecessary updates
+
+		s.getTransaction().rollback();
+	}
+}

hibernate-core/src/test/java/org/hibernate/test/component/empty/EmptyInitializedCompositesDirtynessTest.java

@@ -0,0 +1,61 @@
+/*
+ * 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.test.component.empty;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+
+import org.hibernate.Session;
+import org.hibernate.cfg.Configuration;
+import org.hibernate.cfg.Environment;
+import org.hibernate.testing.TestForIssue;
+import org.hibernate.testing.junit4.BaseCoreFunctionalTestCase;
+import org.junit.Test;
+
+/**
+ * Test class for empty embedded dirtiness computation.
+ *
+ * @author Laurent Almeras
+ */
+public class EmptyInitializedCompositesDirtynessTest extends BaseCoreFunctionalTestCase {
+
+	@Override
+	protected Class<?>[] getAnnotatedClasses() {
+		return new Class[] { ComponentEmptyEmbeddedOwner.class, ComponentEmptyEmbedded.class };
+	}
+
+	@Override
+	protected void configure(Configuration configuration) {
+		super.configure( configuration );
+		configuration.getProperties().put( Environment.CREATE_EMPTY_COMPOSITES_ENABLED, Boolean.valueOf( true ) );
+	}
+
+	/**
+	 * Test for dirtyness computation consistency when a property is an empty composite and that empty composite
+	 * initialization is set.
+	 */
+	@Test
+	@TestForIssue(jiraKey = "HHH-7610")
+	public void testInitializedCompositesEmpty() {
+		Session s = openSession();
+		s.getTransaction().begin();
+
+		ComponentEmptyEmbeddedOwner owner = new ComponentEmptyEmbeddedOwner();
+		s.persist( owner );
+
+		s.flush();
+		s.getTransaction().commit();
+
+		s.clear();
+		s.getTransaction().begin();
+		owner = (ComponentEmptyEmbeddedOwner) s.get( ComponentEmptyEmbeddedOwner.class, owner.getId() );
+		assertNotNull( owner.getEmbedded() );
+		assertFalse( s.isDirty() );
+
+		s.getTransaction().rollback();
+	}
+}

hibernate-core/src/test/java/org/hibernate/test/component/empty/EmptyInitializedCompositesTest.java

@@ -0,0 +1,63 @@
+/*
+ * 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.test.component.empty;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+
+import org.hibernate.Session;
+import org.hibernate.cfg.Configuration;
+import org.hibernate.cfg.Environment;
+import org.hibernate.testing.TestForIssue;
+import org.hibernate.testing.junit4.BaseCoreFunctionalTestCase;
+import org.junit.Test;
+
+/**
+ * Test class for empty embedded dirtiness computation.
+ *
+ * @author Laurent Almeras
+ */
+public class EmptyInitializedCompositesTest extends BaseCoreFunctionalTestCase {
+
+	@Override
+	protected Class<?>[] getAnnotatedClasses() {
+		return new Class[] { ComponentEmptyEmbeddedOwner.class, ComponentEmptyEmbedded.class };
+	}
+
+	@Override
+	protected void configure(Configuration configuration) {
+		super.configure( configuration );
+		configuration.getProperties().put( Environment.CREATE_EMPTY_COMPOSITES_ENABLED, Boolean.valueOf( true ) );
+	}
+
+	/**
+	 * Test empty composite initialization.
+	 */
+	@Test
+	@TestForIssue(jiraKey = "HHH-7610")
+	public void testCompositesEmpty() {
+		Session s = openSession();
+		s.getTransaction().begin();
+
+		ComponentEmptyEmbeddedOwner owner = new ComponentEmptyEmbeddedOwner();
+		s.persist( owner );
+
+		s.flush();
+		s.getTransaction().commit();
+
+		s.clear();
+		s.getTransaction().begin();
+		owner = (ComponentEmptyEmbeddedOwner) s.get( ComponentEmptyEmbeddedOwner.class, owner.getId() );
+		assertNotNull( owner.getEmbedded() );
+		assertFalse( s.isDirty() );
+
+		owner.setEmbedded( null );
+		assertFalse( s.isDirty() ); // must be false to avoid unnecessary updates
+
+		s.getTransaction().rollback();
+	}
+}