Fixing stuff as requested

Author: ldusan84

lib/internal/Magento/Framework/App/Feed.php

@@ -27,12 +27,12 @@ public function __construct(
      * 
      * @return string
      */
-    public function getFormatedContentAs(
-        $format = self::DEFAULT_FORMAT
+    public function getFormattedContentAs(
+        $format = self::FORMAT_XML
     ) {
         $feed = $this->feed::importArray(
             $this->data, 
-            FeedFactoryInterface::DEFAULT_FORMAT
+            FeedFactoryInterface::FORMAT_RSS
         );
         return $this->feed->saveXml();
     }

lib/internal/Magento/Framework/App/FeedFactory.php

@@ -27,7 +27,7 @@ class FeedFactory implements FeedFactoryInterface
     /**
      * @var ObjectManagerInterface
      */
-    protected $objectManager;
+    private $objectManager;
 
     /**
      * @param ObjectManagerInterface $objectManger
@@ -54,22 +54,30 @@ public function __construct(
      */
     public function create(
         array $data, 
-        $format = FeedFactoryInterface::DEFAULT_FORMAT
+        $format = FeedFactoryInterface::FORMAT_RSS
     ) {
         if (!isset($this->formats[$format])) {
             throw new \Magento\Framework\Exception\InputException(
                 __('The format is not supported'),
                 $e
             );
         }
+
+        if (!is_subclass_of($this->formats[$format], '\Magento\Framework\App\FeedInterface')) {
+            throw new \Magento\Framework\Exception\InputException(
+                __('Wrong format handler type'),
+                $e
+            );   
+        }
+
         try {
             return $this->objectManager->create(
                 $this->formats[$format],
                 $data
             );
         } catch (\Exception $e) {
             $this->logger->error($e->getMessage());
-            throw new \Magento\Framework\Exception\InputException(
+            throw new \Magento\Framework\Exception\RuntimeException(
                 __('There has been an error with import'),
                 $e
             );

lib/internal/Magento/Framework/App/FeedFactoryInterface.php

@@ -8,7 +8,7 @@
 interface FeedFactoryInterface
 {
 
-    const DEFAULT_FORMAT = 'rss';
+    const FORMAT_RSS = 'rss';
 
     /**
      * Returns FeedInterface object from a custom array
@@ -20,6 +20,6 @@ interface FeedFactoryInterface
      */
     public function create(
         array $data, 
-        $format = self::DEFAULT_FORMAT
+        $format = self::FORMAT_RSS
     );
 }

lib/internal/Magento/Framework/App/FeedInterface.php

@@ -7,12 +7,12 @@
 
 interface FeedInterface
 {
-    const DEFAULT_FORMAT = 'xml';
+    const FORMAT_XML = 'xml';
 
     /**
      * @return string
      */
     public function getFormattedContentAs(
-        $format = self::DEFAULT_FORMAT
+        $format = self::FORMAT_XML
     );
 }