Fixed potential NPE in SharedEntityManagerCreator

Fix SharedEntityManagerCreator.createSharedEntityManager to correctly
forward an empty array in case that EntityManagerFactoryInfo returns
null from getEntityManagerInterface().

Previously the var-args invocation had turned null into an array with
a null value which caused a NullPointerException in the call to
Proxy.newProxyInstance() further down the call stack.

Issue: SPR-10678

spring-orm/src/main/java/org/springframework/orm/jpa/SharedEntityManagerCreator.java

@@ -24,13 +24,13 @@ import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.lang.reflect.Proxy;
 import java.util.Map;
+
 import javax.persistence.EntityManager;
 import javax.persistence.EntityManagerFactory;
 import javax.persistence.Query;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
-
 import org.springframework.util.ClassUtils;
 import org.springframework.util.CollectionUtils;
 
@@ -46,12 +46,16 @@ import org.springframework.util.CollectionUtils;
  *
  * @author Juergen Hoeller
  * @author Rod Johnson
+ * @author Oliver Gierke
  * @since 2.0
  * @see org.springframework.orm.jpa.LocalEntityManagerFactoryBean
  * @see org.springframework.orm.jpa.JpaTransactionManager
  */
 public abstract class SharedEntityManagerCreator {
 
+	private static final Class<?>[] NO_ENTITY_MANAGER_INTERFACES = new Class<?>[0];
+
+
 	/**
 	 * Create a transactional EntityManager proxy for the given EntityManagerFactory,
 	 * automatically joining ongoing transactions.
@@ -84,10 +88,11 @@ public abstract class SharedEntityManagerCreator {
 	 */
 	public static EntityManager createSharedEntityManager(
 			EntityManagerFactory emf, Map properties, boolean synchronizedWithTransaction) {
-
-		Class emIfc = (emf instanceof EntityManagerFactoryInfo ?
+		Class<?> entityManagerInterface = (emf instanceof EntityManagerFactoryInfo ?
 				((EntityManagerFactoryInfo) emf).getEntityManagerInterface() : EntityManager.class);
-		return createSharedEntityManager(emf, properties, synchronizedWithTransaction, emIfc);
+		return createSharedEntityManager(emf, properties, synchronizedWithTransaction, 
+				(entityManagerInterface == null ? NO_ENTITY_MANAGER_INTERFACES : 
+					new Class<?>[] { entityManagerInterface }));
 	}
 
 	/**

spring-orm/src/test/java/org/springframework/orm/jpa/SharedEntityManagerCreatorTests.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2002-2013 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.orm.jpa;
+
+import javax.persistence.EntityManagerFactory;
+
+import org.junit.Test;
+
+import static org.hamcrest.CoreMatchers.*;
+import static org.junit.Assert.*;
+import static org.mockito.Mockito.*;
+
+/**
+ * Unit tests for {@link SharedEntityManagerCreator}.
+ * 
+ * @author Oliver Gierke
+ */
+public class SharedEntityManagerCreatorTests {
+
+	@Test
+	public void proxyingWorksIfInfoReturnsNullEntityManagerInterface() {
+		EntityManagerFactory emf = mock(EntityManagerFactory.class,
+				withSettings().extraInterfaces(EntityManagerFactoryInfo.class));
+		// EntityManagerFactoryInfo.getEntityManagerInterface returns null
+		assertThat(SharedEntityManagerCreator.createSharedEntityManager(emf),
+				is(notNullValue()));
+	}
+
+}