Use isolated Hibernate EntityManager for AOT contribution.

Closes #3876

Author: mp911de

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/aot/JpaRepositoryContributor.java

@@ -68,6 +68,7 @@ public class JpaRepositoryContributor extends RepositoryContributor {
 	private final EntityGraphLookup entityGraphLookup;
 
 	public JpaRepositoryContributor(AotRepositoryContext repositoryContext) {
+
 		super(repositoryContext);
 
 		AotMetamodel amm = new AotMetamodel(repositoryContext.getResolvedTypes());
@@ -78,6 +79,7 @@ public JpaRepositoryContributor(AotRepositoryContext repositoryContext) {
 	}
 
 	public JpaRepositoryContributor(AotRepositoryContext repositoryContext, EntityManagerFactory entityManagerFactory) {
+
 		super(repositoryContext);
 
 		this.persistenceProvider = PersistenceProvider.fromEntityManagerFactory(entityManagerFactory);

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/config/JpaRepositoryConfigExtension.java

@@ -325,6 +325,8 @@ static boolean isActive(@Nullable ClassLoader classLoader) {
 	 */
 	public static class JpaRepositoryRegistrationAotProcessor extends RepositoryRegistrationAotProcessor {
 
+		String GENERATED_REPOSITORIES_JPA_USE_ENTITY_MANAGER = "spring.aot.jpa.repositories.use-entitymanager";
+
 		protected @Nullable RepositoryContributor contribute(AotRepositoryContext repositoryContext,
 				GenerationContext generationContext) {
 
@@ -334,11 +336,20 @@ public static class JpaRepositoryRegistrationAotProcessor extends RepositoryRegi
 				return null;
 			}
 
-			ConfigurableListableBeanFactory beanFactory = repositoryContext.getBeanFactory();
-			EntityManagerFactory emf = beanFactory.getBeanProvider(EntityManagerFactory.class).getIfAvailable();
+			boolean useEntityManager = Boolean.parseBoolean(
+					repositoryContext.getEnvironment().getProperty(GENERATED_REPOSITORIES_JPA_USE_ENTITY_MANAGER, "false"));
+
+			if (useEntityManager) {
+
+				ConfigurableListableBeanFactory beanFactory = repositoryContext.getBeanFactory();
+				EntityManagerFactory emf = beanFactory.getBeanProvider(EntityManagerFactory.class).getIfAvailable();
+
+				if (emf != null) {
+					return new JpaRepositoryContributor(repositoryContext, emf);
+				}
+			}
 
-			return emf != null ? new JpaRepositoryContributor(repositoryContext, emf)
-					: new JpaRepositoryContributor(repositoryContext);
+			return new JpaRepositoryContributor(repositoryContext);
 		}
 	}
 }