12 September 2012

Fun with CQ5: 2

We follow Adobe's recommendation to use the tag structure to represent menu navigation. Thus, pages can be organized in the content tree the way that is convenient for authors to work (or perhaps to enforce some design restrictions by template), while menus can evolve flexibly in response to usability testing or can differ depending on platform (desktop vs. mobile).

So to render a menu, it's a typical coding pattern to walk a subtree of tags, and for each one, find its corresponding web page (Node) and render its hyperlink. The only tricky bit is that com.day.cq.tagging.Tag.find() returns both Nodes that are explcitly marked with the specified tag as well as Nodes that are only subordinate to a Node that is assigned the tag. A lot of the time, you just want Nodes of the first kind.

We had been using a scheme that matched the Node's navigation title to the tag's title, but that pattern broke down when authors started designing menu items with duplicate names. (And there were other wrinkles.) So, after some desperate Friday afternoon whiteboard sketching, I realized that we could inquire of each candidate Node what tags were assigned to it explicitly, and test for an exact match of TagIDs. And I cooked up the following method, stripped of exception handling, debugging logic, and a little project-specific stuff. The cq:tags property is multi-valued, so there's a little more messy object navigation than you might expect.

import com.day.cq.tagging.Tag;
import java.util.Iterator;
import javax.jcr.Node;
import javax.jcr.Property;
import javax.jcr.PropertyIterator;
import javax.jcr.Value;
import org.apache.sling.api.resource.Resource;

* * * 

     * Returns the node tagged with the specified tag; if there is more than one such node, returns
     * one of them arbitrarily.  The node must have the tag assigned directly to it as a property;
     * nodes that are tagged by inheritance in the content tree are ignored.
     * @param tag
     * @return node: the node tagged with the specified tag, or null
    public static Node getMatchingNode(Tag tag) {
        Node matchingNode = null;
        Iterator<Resource> relatedNodes = tag.find();
        while (relatedNodes.hasNext() && matchingNode == null) {
            Node node = relatedNodes.next().adaptTo(Node.class);
            PropertyIterator tagIds = node.getProperties("cq:tags");
            while (tagIds.hasNext()) {
                Property property = tagIds.nextProperty();
                Value values[] = property.getValues();
                for (Value value : values) {
                    String id = value.getString();
                    if (id.equals(tag.getTagID())) {
                        matchingNode = node;
                        break outer;
        return matchingNode;