Building Tagging into AEM Applications

For the purpose of programmatically working with tags or extending tags within a custom AEM application, this document describes use of the

• Tagging API

that interacts with the

• Tagging framework

For related information regarding tagging:

• See Using Tags for information about tagging content as a content author.
• See Administering Tags for an administrator?s perspective about creating and managing tags, as well as to which content tags have been applied.

Overview of the Tagging API

The implementation of the tagging framework in AEM allows management of tags and tag content using the JCR API. TagManager ensures that tags entered as values on the cq:tags string array property are not duplicated, it removes TagIDs pointing to non-existing tags and updates TagIDs for moved or merged tags. TagManager uses a JCR observation listener that reverts any incorrect changes. The main classes are in the com.day.cq.tagging package:

• JcrTagManagerFactory - returns a JCR-based implementation of a TagManager. It is the reference implementation of the Tagging API.
• TagManager - allows for resolving and creating tags by paths and names.
• Tag - defines the tag object.

Getting a JCR-based TagManager

To retrieve a TagManager instance, you need to have a JCR Session and to call getTagManager(Session):

@Reference
JcrTagManagerFactory jcrTagManagerFactory;

TagManager tagManager = jcrTagManagerFactory.getTagManager(session);

In the typical Sling context you can also adapt to a TagManager from the ResourceResolver:

TagManager tagManager = resourceResolver.adaptTo(TagManager.class);

Retrieving a Tag object

A Tag can be retrieved through the TagManager, by either resolving an existing tag or creating a new one:

Tag tag = tagManager.resolve("my/tag"); // for existing tags

Tag tag = tagManager.createTag("my/tag"); // for new tags

For the JCR-based implementation, which maps Tags onto JCR Nodes, you can directly use Sling’s adaptTo mechanism if you have the resource (e.g. such as /content/cq:tags/default/my/tag):

Tag tag = resource.adaptTo(Tag.class);

While a tag may only be converted from a resource (not a node), a tag can be converted to both a node and a resource:

Node node = tag.adaptTo(Node.class);
Resource node = tag.adaptTo(Resource.class);

Getting and Setting Tags

// Getting the tags of a Resource:
Tag[] tags = tagManager.getTags(resource);

// Setting tags to a Resource:
tagManager.setTags(resource, tags);

Searching for Tags

// Searching for the Resource objects that are tagged with the tag object:
Iterator<Resource> it = tag.find();

// Retrieving the usage count of the tag object:
long count = tag.getCount();

// Searching for the Resource objects that are tagged with the tagID String:
 RangeIterator<Resource> it = tagManager.find(tagID);

Deleting Tags

tagManager.deleteTag(tag);

Replicating Tags

It is possible to use the replication service (Replicator) with tags because tags are of type nt:hierarchyNode:

replicator.replicate(session, replicationActionType, tagPath);

The Tag Garbage Collector

The tag garbage collector is a background service that cleans up the tags that are hidden and unused. Hidden and unused tags are tags below /content/cq:tags that have a cq:movedTo property and are not used on a content node. They have a count of zero. By using this lazy deletion process, the content node (i.e. the cq:tags property) does not have to be updated as part of the move or the merge operation. The references in the cq:tags property are automatically updated when the cq:tags property is updated, e.g. through the page properties dialog.

The tag garbage collector runs by default once a day. This can be configured at:

http://<host>:<port>/system/console/configMgr/com.day.cq.tagging.impl.TagGarbageCollector

Tag Search and Tag Listing

The search for tags and the tag listing work as follows:

• The search for TagID searches for the tags that have the property cq:movedTo set to TagID and follows through the cq:movedTo TagIDs.
• The search for tag title only searches the tags that do not have a cq:movedTo property.

Tags in Different Languages

A tag title can be defined in different languages. A language sensitive property is then added to the tag node. This property has the format jcr:title.<locale>, e.g. jcr:title.fr for the French translation. <locale> must be a lower case ISO locale string and use underscore (_) instead of hyphen/dash (-), for example: de_ch.

For example when the Animals tag is added to the Products page, the value stockphotography:animals is added to the property cq:tags of the node /content/wknd/en/products/jcr:content. The translation is referenced from the tag node.

The server-side API has localized title-related methods:

• com.day.cq.tagging.Tag
  • getLocalizedTitle(Locale locale)
  • getLocalizedTitlePaths()
  • getLocalizedTitles()
  • getTitle(Locale locale)
  • getTitlePath(Locale locale)
• com.day.cq.tagging.TagManager
  • canCreateTagByTitle(String tagTitlePath, Locale locale)
  • createTagByTitle(String tagTitlePath, Locale locale)
  • resolveByTitle(String tagTitlePath, Locale locale)

In AEM, the language can be obtained either from the page language or from the user language.

For tagging, localization depends on the context as tag titles can be displayed in the page language, in the user language or in any other language.

Adding a New Language to the Edit Tag Dialog

The following procedure describes how to add a new language (e.g. Finnish) to the Tag Edit dialog:

1. In CRXDE, edit the multi-value property languages of the node /content/cq:tags.
2. Add fi_fi, which represents the Finnish locale, and save the changes.

Finnish is now available in the tag dialog of the page properties and in the Edit Tag dialog when editing a tag in the Tagging console.

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