TUL/ The context user is set to current subscriber (#747)

* The context user is set to current subscriber

* Updated comment

* Fixed checktyle issue

Author: milanmajchrak

dspace-api/src/main/java/org/dspace/subscriptions/SubscriptionEmailNotificationServiceImpl.java

@@ -67,6 +67,7 @@ public SubscriptionEmailNotificationServiceImpl(Map<String, DSpaceObjectUpdates>
     public void perform(Context context, DSpaceRunnableHandler handler, String subscriptionType, String frequency) {
         List<IndexableObject> communityItems = new ArrayList<>();
         List<IndexableObject> collectionsItems = new ArrayList<>();
+        EPerson currentEperson = context.getCurrentUser();
         try {
             List<Subscription> subscriptions =
                                findAllSubscriptionsBySubscriptionTypeAndFrequency(context, subscriptionType, frequency);
@@ -77,7 +78,10 @@ public void perform(Context context, DSpaceRunnableHandler handler, String subsc
                 for (Subscription subscription : subscriptions) {
                     DSpaceObject dSpaceObject = subscription.getDSpaceObject();
                     EPerson ePerson = subscription.getEPerson();
-
+                    // Set the current user to the subscribed eperson because the Solr query checks
+                    // the permissions of the current user in the ANONYMOUS group.
+                    // If there is no user (i.e., `current user = null`), it will send an email with no new items.
+                    context.setCurrentUser(ePerson);
                     if (!authorizeService.authorizeActionBoolean(context, ePerson, dSpaceObject, READ, true)) {
                         iterator++;
                         continue;
@@ -126,6 +130,8 @@ public void perform(Context context, DSpaceRunnableHandler handler, String subsc
             handler.handleException(e);
             context.abort();
         }
+        // Reset the current user because it was changed to subscriber eperson
+        context.setCurrentUser(currentEperson);
     }
 
     @SuppressWarnings("rawtypes")