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A DD4T.net Implementation - Taxonomy Factory

I have noticed that in all my recent projects, there is a strong need for an easy and well performing way of handling taxonomies. Functionality ranges from being able to read a Keyword in a taxonomy, to traverse the child/parent relationships, to read metadata on a Keyword and also to read related Components tagged against a Keyword.

In order to provide these features, I implemented a DD4T factory that deals with Tridion taxonomies. Namely, I created the ITaxonomyFactory that defines certain method signatures. I'm using Ninject to bind the interface to an actual implementing class, so using this in DD4T context is trivial.

public interface ITaxonomyFactory
{
    MyKeyword GetTaxonomy(string taxonomyXmlNameOrUri);
    MyKeyword GetKeywordByUri(MyKeyword root, string uri);
}

The factory class uses the TaxonomyFactory and TaxonomyRelationManager to interact with the data published to the Content Delivery database.

Method GetTaxonomy takes either a Taxonomy XML name, as defined in Tridion CMS (which is resolved using the labels mechanism described in post Everything's a Label) or TcmUri of a Tridion Category.

The method uses the CacheWrapper described in post A Simple TTL Cache, in order to store either a root Keyword object or a null value for a given amount of time.

The returned value, MyKeyword, is a specialization object of DD4T.ContentModel.IKeyword, which will be described in a follow-up post.

public class MyTaxonomyFactory : ITaxonomyFactory
{
    [Inject]
    public virtual ICacheWrapper CacheWrapper { get; set; }

    private TaxonomyFactory taxonomyFactory;
    private TaxonomyRelationManager manager;

    public MyTaxonomyFactory()
    {
        taxonomyFactory = new TaxonomyFactory();
        manager = new TaxonomyRelationManager();
    }

    public MyKeyword GetTaxonomy(string taxonomyXmlNameOrUri)
    {
        MyKeyword result;
        object cacheElement;
        string taxonomyUri = DD4TResourceProvider.GetTaxonomyLabel(taxonomyXmlNameOrUri);
        string key = "category" + taxonomyUri;

        if (CacheWrapper.TryGet(key, out cacheElement))
        {
            result = cacheElement as MyKeyword;
        }
        else
        {
            tridion.Keyword tridionKeyword = taxonomyFactory.GetTaxonomyKeywords(taxonomyUri);
            if (tridionKeyword == null)
            {
                result = null;
                CacheWrapper.Insert(key, false, 1);
            }
            else
            {
                TaxonomyConverter taxonomyConverter = new TaxonomyConverter();
                result = taxonomyConverter.ConvertToDD4T(tridionKeyword);
                CacheWrapper.Insert(key, result, 60);
            }
        }

        return result;
    }

Method GetKeywordByUri is a simple traversal method starting from a keyword in the taxonomy and searching depth-first for a keyword whose TcmUri matches a TcmUri we look for. The implementation makes use of a fancy delegate method, through which we can easily supply different comparison logic. The KeywordComparer returns a boolean result from comparing two Keywords. In the GetKeywordByUri method, we simply provide a comparer that only checks the keywords TcmUri. This mechanism is very flexible and easy to extend for other types of comparisons, for example by keyword title, key or even some custom meta field.

private delegate bool KeywordComparer(MyKeyword keyword);

public MyKeyword GetKeywordByUri(MyKeyword root, string uri)
{
    return SearchKeyword(root, delegate(MyKeyword keyword)
    {
        return keyword != null && keyword.Id.Equals(uri);
    });
}

private MyKeyword SearchKeyword(MyKeyword root, KeywordComparer keywordComparer)
{
    if (keywordComparer(root))
    {
        return root;
    }

    foreach (MyKeyword childKeyword in root.ChildKeywords)
    {
        MyKeyword result = SearchKeyword(childKeyword, keywordComparer);
        if (result != null)
        {
            return result;
        }
    }

    return null;
}

As an example, the following code snippet reads a taxonomy and a given keyword in it:

    ITaxonomyFactory factory = 
            DependencyResolver.Current.GetService<ITaxonomyFactory>();
    MyKeyword root = factory.GetTaxonomy("Product-Catalog");
    MyKeyword product = factory.GetKeywordByUri(root, "tcm:123-456-1024");


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