HHH-16952 Discover embeddable types through @Embedded annotation for enhancement in a pre-discovery phase

hibernate-core/src/main/java/org/hibernate/jpa/boot/internal/EntityManagerFactoryBuilderImpl.java

@@ -341,13 +341,12 @@ public class EntityManagerFactoryBuilderImpl implements EntityManagerFactoryBuil
 				);
 
 				persistenceUnit.pushClassTransformer( enhancementContext );
-
+				final ClassTransformer classTransformer = persistenceUnit.getClassTransformer();
-				if ( !persistenceUnit.getClassTransformers().isEmpty() ) {
+				if ( classTransformer != null ) {
 					final ClassLoader classLoader = persistenceUnit.getTempClassLoader();
 					if ( classLoader == null ) {
 						throw persistenceException( "Enhancement requires a temp class loader, but none was given." );
 					}
-					for ( ClassTransformer classTransformer : persistenceUnit.getClassTransformers() ) {
 					for ( PersistentClass entityBinding : metadata.getEntityBindings() ) {
 						if ( entityBinding.getClassName() != null ) {
 							classTransformer.discoverTypes( classLoader, entityBinding.getClassName() );
@@ -355,7 +354,6 @@ public class EntityManagerFactoryBuilderImpl implements EntityManagerFactoryBuil
 					}
 				}
 			}
-			}
 
 			// for the time being we want to revoke access to the temp ClassLoader if one was passed
 			metamodelBuilder.applyTempClassLoader( null );

hibernate-core/src/main/java/org/hibernate/jpa/boot/internal/ParsedPersistenceXmlDescriptor.java

@@ -194,7 +194,7 @@ public class ParsedPersistenceXmlDescriptor implements org.hibernate.jpa.boot.sp
 	}
 
 	@Override
-	public Collection<ClassTransformer> getClassTransformers() {
+	public ClassTransformer getClassTransformer() {
-		return Collections.emptyList();
+		return null;
 	}
 }

hibernate-core/src/main/java/org/hibernate/jpa/boot/internal/PersistenceUnitInfoDescriptor.java

@@ -11,6 +11,8 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 import java.util.Properties;
+
+import jakarta.persistence.PersistenceException;
 import jakarta.persistence.SharedCacheMode;
 import jakarta.persistence.ValidationMode;
 import jakarta.persistence.spi.PersistenceUnitInfo;
@@ -26,7 +28,7 @@ import org.hibernate.jpa.internal.enhance.EnhancingClassTransformerImpl;
  */
 public class PersistenceUnitInfoDescriptor implements PersistenceUnitDescriptor {
 	private final PersistenceUnitInfo persistenceUnitInfo;
-	private final ArrayList<ClassTransformer> classTransformers = new ArrayList<>();
+	private ClassTransformer classTransformer;
 
 	public PersistenceUnitInfoDescriptor(PersistenceUnitInfo persistenceUnitInfo) {
 		this.persistenceUnitInfo = persistenceUnitInfo;
@@ -114,16 +116,19 @@ public class PersistenceUnitInfoDescriptor implements PersistenceUnitDescriptor
 
 	@Override
 	public void pushClassTransformer(EnhancementContext enhancementContext) {
+		if ( this.classTransformer != null ) {
+			throw new PersistenceException( "Persistence unit [" + persistenceUnitInfo.getPersistenceUnitName() + "] can only have a single class transformer." );
+		}
 		// During testing, we will return a null temp class loader in cases where we don't care about enhancement
 		if ( persistenceUnitInfo.getNewTempClassLoader() != null ) {
 			final EnhancingClassTransformerImpl classTransformer = new EnhancingClassTransformerImpl( enhancementContext );
-			classTransformers.add( classTransformer );
+			this.classTransformer = classTransformer;
 			persistenceUnitInfo.addTransformer( classTransformer );
 		}
 	}
 
 	@Override
-	public Collection<ClassTransformer> getClassTransformers() {
+	public ClassTransformer getClassTransformer() {
-		return classTransformers;
+		return classTransformer;
 	}
 }

hibernate-core/src/main/java/org/hibernate/jpa/boot/spi/PersistenceUnitDescriptor.java

@@ -88,5 +88,5 @@ public interface PersistenceUnitDescriptor {
 
 	void pushClassTransformer(EnhancementContext enhancementContext);
 
-	Collection<ClassTransformer> getClassTransformers();
+	ClassTransformer getClassTransformer();
 }

hibernate-core/src/test/java/org/hibernate/orm/test/exceptionhandling/BaseJpaOrNativeBootstrapFunctionalTestCase.java

@@ -253,8 +253,8 @@ public abstract class BaseJpaOrNativeBootstrapFunctionalTestCase extends BaseUni
 		}
 
 		@Override
-		public Collection<ClassTransformer> getClassTransformers() {
+		public ClassTransformer getClassTransformer() {
-			return Collections.emptyList();
+			return null;
 		}
 	}
 

hibernate-core/src/test/java/org/hibernate/orm/test/jpa/BaseEntityManagerFunctionalTestCase.java

@@ -191,8 +191,8 @@ public abstract class BaseEntityManagerFunctionalTestCase extends BaseUnitTestCa
 		}
 
 		@Override
-		public Collection<ClassTransformer> getClassTransformers() {
+		public ClassTransformer getClassTransformer() {
-			return Collections.emptyList();
+			return null;
 		}
 	}
 

hibernate-testing/src/main/java/org/hibernate/testing/orm/jpa/PersistenceUnitDescriptorAdapter.java

@@ -116,7 +116,7 @@ public class PersistenceUnitDescriptorAdapter implements PersistenceUnitDescript
 	}
 
 	@Override
-	public Collection<ClassTransformer> getClassTransformers() {
+	public ClassTransformer getClassTransformer() {
-		return Collections.emptyList();
+		return null;
 	}
 }

hibernate-testing/src/main/java/org/hibernate/testing/orm/junit/EntityManagerFactoryBasedFunctionalTest.java

@@ -271,8 +271,8 @@ public class EntityManagerFactoryBasedFunctionalTest
 		}
 
 		@Override
-		public Collection<ClassTransformer> getClassTransformers() {
+		public ClassTransformer getClassTransformer() {
-			return Collections.emptyList();
+			return null;
 		}
 	}