Update ensureNotIterable check for inserts.

Check if an object is an array or is an instance of collection or iterator instead of checking against collection names which is likely to never work.

Closes #2911
Original Pull Request: #590

Author: GotoFinal

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/MongoTemplate.java

@@ -157,22 +157,12 @@
  * @author Roman Puchkovskiy
  * @author Yadhukrishna S Pai
  * @author Anton Barkan
+ * @author Bartłomiej Mazur
  */
 public class MongoTemplate implements MongoOperations, ApplicationContextAware, IndexOperationsProvider {
 
 	private static final Logger LOGGER = LoggerFactory.getLogger(MongoTemplate.class);
 	private static final WriteResultChecking DEFAULT_WRITE_RESULT_CHECKING = WriteResultChecking.NONE;
-	private static final Collection<String> ITERABLE_CLASSES;
-
-	static {
-
-		Set<String> iterableClasses = new HashSet<>();
-		iterableClasses.add(List.class.getName());
-		iterableClasses.add(Collection.class.getName());
-		iterableClasses.add(Iterator.class.getName());
-
-		ITERABLE_CLASSES = Collections.unmodifiableCollection(iterableClasses);
-	}
 
 	private final MongoConverter mongoConverter;
 	private final MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> mappingContext;
@@ -1164,7 +1154,7 @@ public <T> T insert(T objectToSave) {
 
 		Assert.notNull(objectToSave, "ObjectToSave must not be null!");
 
-		ensureNotIterable(objectToSave);
+		ensureNotAnArrayOrCollection(objectToSave);
 		return insert(objectToSave, getCollectionName(ClassUtils.getUserClass(objectToSave)));
 	}
 
@@ -1179,13 +1169,13 @@ public <T> T insert(T objectToSave, String collectionName) {
 		Assert.notNull(objectToSave, "ObjectToSave must not be null!");
 		Assert.notNull(collectionName, "CollectionName must not be null!");
 
-		ensureNotIterable(objectToSave);
+		ensureNotAnArrayOrCollection(objectToSave);
 		return (T) doInsert(collectionName, objectToSave, this.mongoConverter);
 	}
 
-	protected void ensureNotIterable(@Nullable Object o) {
-		if (o != null) {
-			if (o.getClass().isArray() || ITERABLE_CLASSES.contains(o.getClass().getName())) {
+	protected void ensureNotAnArrayOrCollection(@Nullable Object o) {
+		if (null != o) {
+			if (o.getClass().isArray() || (o instanceof Collection) || (o instanceof Iterator)) {
 				throw new IllegalArgumentException("Cannot use a collection here.");
 			}
 		}