HHH-18829 Hibernate Core: use ID class generated by Hibernate Processor when class is not annotated with @IdClass, but have more than one member annotated with @id

Author: cigaly

hibernate-core/src/main/java/org/hibernate/boot/model/internal/EntityBinder.java

@@ -483,10 +483,17 @@ private boolean mapAsIdClass(
 		final ClassDetails classWithIdClass = inheritanceState.getClassWithIdClass( false );
 		if ( classWithIdClass != null ) {
 			final IdClass idClassAnn = classWithIdClass.getDirectAnnotationUsage( IdClass.class );
-			final Class<?> idClassValue = idClassAnn.value();
-			final ClassDetails compositeClass =
-					getMetadataCollector().getSourceModelBuildingContext().getClassDetailsRegistry()
-							.resolveClassDetails( idClassValue.getName() );
+			final ClassDetails compositeClass;
+			if ( idClassAnn == null ) {
+				compositeClass = getMetadataCollector().getSourceModelBuildingContext()
+						.getClassDetailsRegistry()
+						.resolveClassDetails( inheritanceState.getClassDetails().getClassName() + "_$Id" );
+			}
+			else {
+				final Class<?> idClassValue = idClassAnn.value();
+				compositeClass = getMetadataCollector().getSourceModelBuildingContext()
+						.getClassDetailsRegistry().resolveClassDetails( idClassValue.getName() );
+			}
 			final TypeDetails compositeType = new ClassTypeDetailsImpl( compositeClass, TypeDetails.Kind.CLASS );
 			final TypeDetails classWithIdType = new ClassTypeDetailsImpl( classWithIdClass, TypeDetails.Kind.CLASS );
 

hibernate-core/src/main/java/org/hibernate/boot/model/internal/InheritanceState.java

@@ -7,6 +7,7 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
+import java.util.stream.Stream;
 
 import org.hibernate.AnnotationException;
 import org.hibernate.boot.spi.AccessType;
@@ -183,6 +184,13 @@ else if ( classDetails.hasDirectAnnotationUsage( IdClass.class ) ) {
 			return classDetails;
 		}
 		else {
+			final long count = Stream.concat(
+					classDetails.getFields().stream(),
+					classDetails.getMethods().stream()
+			).filter( t -> t.hasDirectAnnotationUsage( Id.class ) ).count();
+			if ( count > 1 ) {
+				return classDetails;
+			}
 			final InheritanceState state = getSuperclassInheritanceState( classDetails, inheritanceStatePerClass );
 			if ( state != null ) {
 				return state.getClassWithIdClass( true );