Fix PersistenceProvider lookup using proxied EntityManagerFactory.

We now distinguish between Spring-proxied and other JDK proxied EntityManagerFactory objects for proper unwrapping. Spring consistently uses a null value as class to get hold of the target object.

Both, Hibernate and EclipseLink fail with a NullPointerException when calling unwrap(null) and therefore, we call all other JDK proxies with unwrap(EntityManagerFactory.class) to adhere to the JPA specification and avoid failures according to the implementations.

Any other proxying mechanism that behaves differently will require additional refinement once such a case comes up.

Closes #3923

Author: mp911de

spring-data-jpa/src/main/java/org/springframework/data/jpa/provider/PersistenceProvider.java

@@ -31,7 +31,6 @@
 import java.util.List;
 import java.util.NoSuchElementException;
 import java.util.Set;
-import java.util.function.LongSupplier;
 import java.util.stream.Stream;
 
 import org.eclipse.persistence.config.QueryHints;
@@ -270,7 +269,10 @@ public static PersistenceProvider fromEntityManagerFactory(EntityManagerFactory
 		while (Proxy.isProxyClass(unwrapped.getClass()) || AopUtils.isAopProxy(unwrapped)) {
 
 			if (Proxy.isProxyClass(unwrapped.getClass())) {
-				unwrapped = unwrapped.unwrap(null);
+
+				Class<EntityManagerFactory> unwrapTo = Proxy.getInvocationHandler(unwrapped).getClass().getName()
+						.contains("org.springframework.orm.jpa.") ? null : EntityManagerFactory.class;
+				unwrapped = unwrapped.unwrap(unwrapTo);
 			} else if (AopUtils.isAopProxy(unwrapped)) {
 				unwrapped = (EntityManagerFactory) AopProxyUtils.getSingletonTarget(unwrapped);
 			}

spring-data-jpa/src/test/java/org/springframework/data/jpa/provider/PersistenceProviderUnitTests.java

@@ -22,7 +22,9 @@
 
 import jakarta.persistence.EntityManager;
 import jakarta.persistence.EntityManagerFactory;
+import jakarta.persistence.PersistenceException;
 
+import java.lang.reflect.Proxy;
 import java.util.Arrays;
 import java.util.Map;
 
@@ -35,6 +37,7 @@
 import org.springframework.asm.ClassWriter;
 import org.springframework.asm.Opcodes;
 import org.springframework.instrument.classloading.ShadowingClassLoader;
+import org.springframework.orm.jpa.AbstractEntityManagerFactoryBean;
 import org.springframework.test.util.ReflectionTestUtils;
 import org.springframework.util.ClassUtils;
 
@@ -110,6 +113,25 @@ void detectsProviderFromProxiedEntityManager() throws Exception {
 		assertThat(fromEntityManager(emProxy)).isEqualTo(ECLIPSELINK);
 	}
 
+	@Test // GH-3923
+	void detectsEntityManagerFromProxiedEntityManagerFactory() throws Exception {
+
+		EntityManagerFactory emf = mockProviderSpecificEntityManagerFactoryInterface(
+				"foo.bar.unknown.jpa.JpaEntityManager");
+		when(emf.unwrap(null)).thenThrow(new NullPointerException());
+		when(emf.unwrap(EntityManagerFactory.class)).thenReturn(emf);
+
+		MyEntityManagerFactoryBean factoryBean = new MyEntityManagerFactoryBean(EntityManagerFactory.class, emf);
+		EntityManagerFactory springProxy = factoryBean.createEntityManagerFactoryProxy(emf);
+
+		Object externalProxy = Proxy.newProxyInstance(getClass().getClassLoader(),
+				new Class[] { EntityManagerFactory.class }, (proxy, method, args) -> method.invoke(emf, args));
+
+		assertThat(PersistenceProvider.fromEntityManagerFactory(springProxy)).isEqualTo(GENERIC_JPA);
+		assertThat(PersistenceProvider.fromEntityManagerFactory((EntityManagerFactory) externalProxy))
+				.isEqualTo(GENERIC_JPA);
+	}
+
 	private EntityManager mockProviderSpecificEntityManagerInterface(String interfaceName) throws ClassNotFoundException {
 
 		Class<?> providerSpecificEntityManagerInterface = InterfaceGenerator.generate(interfaceName, shadowingClassLoader,
@@ -128,7 +150,7 @@ private EntityManagerFactory mockProviderSpecificEntityManagerFactoryInterface(S
 			throws ClassNotFoundException {
 
 		Class<?> providerSpecificEntityManagerInterface = InterfaceGenerator.generate(interfaceName, shadowingClassLoader,
-				EntityManager.class);
+				EntityManagerFactory.class);
 
 		return (EntityManagerFactory) Mockito.mock(providerSpecificEntityManagerInterface);
 	}
@@ -181,4 +203,24 @@ private static String[] toResourcePaths(Class<?>... interfacesToImplement) {
 					.toArray(String[]::new);
 		}
 	}
+
+	static class MyEntityManagerFactoryBean extends AbstractEntityManagerFactoryBean {
+
+		public MyEntityManagerFactoryBean(Class<? extends EntityManagerFactory> entityManagerFactoryInterface,
+				EntityManagerFactory entityManagerFactory) {
+			setEntityManagerFactoryInterface(entityManagerFactoryInterface);
+			ReflectionTestUtils.setField(this, "nativeEntityManagerFactory", entityManagerFactory);
+
+		}
+
+		@Override
+		protected EntityManagerFactory createNativeEntityManagerFactory() throws PersistenceException {
+			return null;
+		}
+
+		@Override
+		protected EntityManagerFactory createEntityManagerFactoryProxy(EntityManagerFactory emf) {
+			return super.createEntityManagerFactoryProxy(emf);
+		}
+	}
 }