Direct reference to JPA 2.1 SynchronizationType enum

Issue: SPR-13481

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

 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -36,6 +36,7 @@ import javax.persistence.EntityManager;
 import javax.persistence.EntityManagerFactory;
 import javax.persistence.PersistenceException;
 import javax.persistence.Query;
+import javax.persistence.SynchronizationType;
 import javax.persistence.spi.PersistenceProvider;
 import javax.persistence.spi.PersistenceUnitInfo;
 import javax.sql.DataSource;
@@ -444,7 +445,7 @@ public abstract class AbstractEntityManagerFactoryBean implements
 			return method.invoke(this, args);
 		}
 		else if (method.getName().equals("createEntityManager") && args != null && args.length > 0 &&
-				args[0] != null && args[0].getClass().isEnum() && "SYNCHRONIZED".equals(args[0].toString())) {
+				args[0] == SynchronizationType.SYNCHRONIZED) {
 			// JPA 2.1's createEntityManager(SynchronizationType, Map)
 			// Redirect to plain createEntityManager and add synchronization semantics through Spring proxy
 			EntityManager rawEntityManager = (args.length > 1 ?