[Port dspace-7_x] subscription email: do not send email if nothing ha…

…s changed (DSpace#9204)

* improved subscriptions email template

(cherry picked from commit 6e7b327)

* do not send emails without content

(cherry picked from commit 926b242)

* fixed coding style violations

(cherry picked from commit fdacec0)

* removed unnecessary isEmpty check as suggested by reviewer

(cherry picked from commit 30a837f)

* moved null check on indexableObjects in generateBodyMail

(cherry picked from commit b43c340)

* fixed unhandled IOException

(cherry picked from commit 9b3f7b6)

* fixed typo in bodyCommunities

(cherry picked from commit ac3d02e)

* do not use != to compare strings

(cherry picked from commit e460183)

* fixed improper handling of empty list

(cherry picked from commit ac72aae)

---------

Co-authored-by: Sascha Szott <[email protected]>

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

@@ -56,8 +56,16 @@ public void notifyForSubscriptions(Context context, EPerson ePerson,
                 Locale supportedLocale = I18nUtil.getEPersonLocale(ePerson);
                 Email email = Email.getEmail(I18nUtil.getEmailFilename(supportedLocale, "subscriptions_content"));
                 email.addRecipient(ePerson.getEmail());
-                email.addArgument(generateBodyMail(context, indexableComm));
-                email.addArgument(generateBodyMail(context, indexableColl));
+
+                String bodyCommunities = generateBodyMail(context, indexableComm);
+                String bodyCollections = generateBodyMail(context, indexableColl);
+                if (bodyCommunities.equals(EMPTY) && bodyCollections.equals(EMPTY)) {
+                    log.debug("subscription(s) of eperson {} do(es) not match any new items: nothing to send" +
+                            " - exit silently", ePerson::getID);
+                    return;
+                }
+                email.addArgument(bodyCommunities);
+                email.addArgument(bodyCollections);
                 email.send();
             }
         } catch (Exception e) {
@@ -67,21 +75,19 @@ public void notifyForSubscriptions(Context context, EPerson ePerson,
     }
 
     private String generateBodyMail(Context context, List<IndexableObject> indexableObjects) {
+        if (indexableObjects == null || indexableObjects.isEmpty()) {
+            return EMPTY;
+        }
         try {
             ByteArrayOutputStream out = new ByteArrayOutputStream();
             out.write("\n".getBytes(UTF_8));
-            if (indexableObjects.size() > 0) {
-                for (IndexableObject indexableObject : indexableObjects) {
-                    out.write("\n".getBytes(UTF_8));
-                    Item item = (Item) indexableObject.getIndexedObject();
-                    String entityType = itemService.getEntityTypeLabel(item);
-                    Optional.ofNullable(entityType2Disseminator.get(entityType))
-                            .orElseGet(() -> entityType2Disseminator.get("Item"))
-                            .disseminate(context, item, out);
-                }
-                return out.toString();
-            } else {
-                out.write("No items".getBytes(UTF_8));
+            for (IndexableObject indexableObject : indexableObjects) {
+                out.write("\n".getBytes(UTF_8));
+                Item item = (Item) indexableObject.getIndexedObject();
+                String entityType = itemService.getEntityTypeLabel(item);
+                Optional.ofNullable(entityType2Disseminator.get(entityType))
+                        .orElseGet(() -> entityType2Disseminator.get("Item"))
+                        .disseminate(context, item, out);
             }
             return out.toString();
         } catch (Exception e) {

dspace/config/emails/subscriptions_content

@@ -2,15 +2,17 @@
 ##
 ## Parameters: {0} Collections updates
 ##             {1} Communities updates
-#set($subject = "${config.get('dspace.name')} Subscription")
-
+#set($subject = "${config.get('dspace.name')} Subscriptions")
 This email is sent from ${config.get('dspace.name')} based on the chosen subscription preferences.
 
-Communities
------------
+#if( not( "$params[0]" == "" ))
+Community Subscriptions:
+------------------------
 List of changed items : ${params[0]}
 
-Collections
------------
+#end
+#if( not( "$params[1]" == "" ))
+Collection Subscriptions:
+-------------------------
 List of changed items : ${params[1]}
-
+#end