External RSS ContentProvider example for #EPiServer, Part three

I’ve experience that it can be tricky setting up content provider. Content Providers in EPiServer is a way of publishing external data as pages/blocks etc. Here is an example of an RSS Content Provider.

This RSSContentProvider derive from an old CMS 6 example of the XMLPageProvider documented here http://world.episerver.com/documentation/Items/Tech-Notes/EPiServer-CMS-6/EPiServer-CMS-60/XmlPageProvider/

episerver-contentprovider-result
Result: listing the RSS as pages

Firstly LoadChildrenReferencesAndTypes is called if not cached, mapping up all the providers ContentReference in EPiServer with MappedIdentity.ConstructExternalIdentifier and IdentityMappingService.

Secondly all ContentReference are call thru LoadContent, where the content is created.

ListMatchingSegments is used by the routing system to match the url segment with the ContentReference.

You’ll need an EPiServer page with equivalent properties “IntroText”, “MainBody” and “DocumentUrl”.

Register the provider in web.config:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
 <episerver>
   <contentProvider>
    <providers>
         <add entryPoint="100" 
          filePath="http://devblog.gosso.se/feed/" 
          name="RSSDevBlog" 
          contentType="Your.EpiPageType.ToUse" 
          type="Gosso.EPiStuff.ContentProviders.RSSContentProvider, Gosso.EPiStuff" />
      </providers>
  </contentProvider>
 </episerver>
</configuration>

RSS Content Provider C# Code:

using EPiServer;
using EPiServer.Core;
using EPiServer.DataAbstraction;
using EPiServer.Security;
using EPiServer.Web;
using EPiServer.Web.Routing;
using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Configuration;
using System.Globalization;
using System.Linq;
using System.Web;
using System.Xml.Linq;

namespace Gosso.EPiStuff.ContentProviders
{
    public class RSSContentProvider : EPiServer.Core.ContentProvider
    {
        private string _filePath;
        private string _contentType;
        private readonly IdentityMappingService _identityMappingService;
        private readonly IContentTypeRepository _contentTypeRepository;
        private readonly IContentFactory _contentFactory;
        private readonly ServiceLocationHelper locator;
        private readonly IUrlSegmentGenerator _urlSegment;
        private readonly CategoryRepository categoryRepository;        
        private readonly IContentCacheKeyCreator _cacheCreator;

        public RSSContentProvider(IdentityMappingService identityMappingService,
            IContentTypeRepository _ContentTypeRepository,
            IContentFactory _ContentFactory,
            ServiceLocationHelper _Locator,
            IUrlSegmentGenerator _UrlSegment, 
            IContentCacheKeyCreator _CacheCreator)
        {
            _identityMappingService = identityMappingService;
            _contentTypeRepository = _ContentTypeRepository;
            _contentFactory = _ContentFactory;
            locator = _Locator;
            _urlSegment = _UrlSegment;
            _cacheCreator = _CacheCreator;
        }

        #region overrides from base class

        /// <summary>
        /// Initializes the provider from configuration settings.
        /// </summary>
        /// <param name="key">The key.</param>
        /// <param name="configParams">The config params.</param>
        public override void Initialize(string key, NameValueCollection configParams)
        {
            //Let base classes do their initialization
            base.Initialize(key, configParams);

            //Make sure a path to the backing xml file is given in configuration of page provider
            if (configParams["filePath"] == null)
            {
                throw new ConfigurationErrorsException("RSSContentProvider requires configuration attribute filePath that should be a application relative path");
            }
            if (configParams["contentType"] == null)
            {
                throw new ConfigurationErrorsException("RSSContentProvider requires configuration attribute contentType that should be ContentType");
            }
            _filePath = HttpUtility.UrlEncode(configParams["filePath"]);
            _contentType = HttpUtility.UrlEncode(configParams["contentType"]);

        }
        
        protected override IContent LoadContent(ContentReference contentLink, ILanguageSelector languageSelector)
        {
            try
            {

                MappedIdentity mappedIdentity = _identityMappingService.Get(contentLink);
                if (mappedIdentity != null && mappedIdentity.ExternalIdentifier != null)
                {   
                    // SOMETIME PARENT IS CALLED FIRST!! breaking change CMS 8 : Possible to set EntryPoint for content provider that have exactly 1 child 

                    string rssGuid = mappedIdentity.ExternalIdentifier.PathAndQuery.TrimStart('/');

                    RSSPage rsspage = (from page in XmlPages.Descendants("item")
                                       where string.Equals(page.GetValue<string>("guid"), rssGuid)
                                       select new RSSPage
                                       {
                                           Guid = page.GetValue<string>("guid"),
                                           Title = page.GetValue<string>("title"),
                                           Description = page.GetValue<string>("description"),
                                           Content = page.GetValue<string>("{http://purl.org/rss/1.0/modules/content/}encoded"),
                                           PubDate = page.GetValue<DateTime>("pubDate"),
                                           Language = page.Parent.Element("language").Value,
                                           DocumentUrl = page.GetAttributeFromElement<string>("enclosure", "url")
                                       }).FirstOrDefault<RSSPage>();


                    if (rsspage != null)
                    {
                        return CreateContent(mappedIdentity, rsspage);
                    }
                    else
                    {
                        //handle
                        return null;
                    }
                }
            }
            catch (Exception)
            {
                
                //handle exception
                
            }

            return null;
        }

        public IContent CreateContent(MappedIdentity mappedIdentity, RSSPage rsspage)
        {
            ContentType type = _contentTypeRepository.Load(Type.GetType(_contentType));
            var mirrored = _contentFactory.CreateContent(type);

            mirrored.ContentTypeID = type.ID;

            mirrored.ParentLink = new PageReference(EntryPoint.ID);

            mirrored.ContentLink = mappedIdentity.ContentLink;
            mirrored.ContentGuid = mappedIdentity.ContentGuid;

            // not this one! May cause loop
            //mirrored.Property["PageLinkURL"].Value = this.ConstructContentUri(contentTypeId, content.ContentLink, content.ContentGuid);

            ILocalizable localizable = mirrored as ILocalizable;
            var langs = new List<CultureInfo>();
            langs.Add(new CultureInfo(rsspage.Language));
            localizable.ExistingLanguages = langs;
            localizable.Language = new CultureInfo(rsspage.Language);
            
            //add date to url segment
            (mirrored as IRoutable).RouteSegment = _urlSegment.GetUrlFriendlySegment(mirrored.Name + "-" + rsspage.PubDate.ToString("yyyy-MM-dd"));

            //add role everyone
            (mirrored as IContentSecurable).GetContentSecurityDescriptor().AddEntry(new AccessControlEntry(EveryoneRole.RoleName, AccessLevel.Read));

            var versionable = mirrored as IVersionable;
            if (versionable != null)
            {
                versionable.Status = VersionStatus.Published;
            }

            PageData pd = new PageData();
            pd = (mirrored as PageData);
            pd.Name = rsspage.Title;
            pd.LinkType = PageShortcutType.Normal;
            string description = HttpUtility.HtmlDecode(rsspage.Description);
            if (!string.IsNullOrWhiteSpace(description))
            {
                pd["IntroText"] = description;
            }

            string content = HttpUtility.HtmlDecode(rsspage.Content);
            if (!string.IsNullOrWhiteSpace(content))
            {
                pd["MainBody"] = content;
            }

            pd.StartPublish = rsspage.PubDate;
            pd["PageChanged"] = rsspage.PubDate;
            pd["PageCreated"] = rsspage.PubDate;
            pd["DocumentUrl"] = rsspage.DocumentUrl;

            //pd["Categories"] = "23,34,233"; //list of categories if you want

            pd.LanguageID = rsspage.Language;

            pd.MakeReadOnly();
            AddContentToCache(mirrored);
            return mirrored;
        }


        protected override IList<GetChildrenReferenceResult> LoadChildrenReferencesAndTypes(ContentReference contentLink, string languageID, out bool languageSpecific)
    {

        languageSpecific = false;
        if (contentLink == this.EntryPoint)
        {

            IList<GetChildrenReferenceResult> list = new List<GetChildrenReferenceResult>();
            try
            {
                List<string> pageLanguages = new List<string>();

                foreach (var page in XmlPages.Descendants("item"))
                {
                    var rsspage = new RSSPage
                    {
                        Guid = page.GetValue<string>("guid"),
                        Title = page.GetValue<string>("title"),
                        Description = page.GetValue<string>("description"),
                        Content = page.GetValue<string>("{http://purl.org/rss/1.0/modules/content/}encoded"),
                        PubDate = page.GetValue<DateTime>("pubDate"),
                        Language = page.Parent.Element("language").Value,
                        DocumentUrl = page.GetAttributeFromElement<string>("enclosure", "url")
                    };

                    try
                    {
                        Uri externalID = MappedIdentity.ConstructExternalIdentifier(ProviderKey, rsspage.Guid);
                        var mappedIdentity = _identityMappingService.Get(externalID, true);

                        if (rsspage != null)
                        {
                                Type modelType = Type.GetType(_contentType);

                                GetChildrenReferenceResult result = new GetChildrenReferenceResult
                            {
                                ContentLink = mappedIdentity.ContentLink,
                                ModelType = modelType,
                                IsLeafNode = true
                            };
                            list.Add(result);

                        }

                    }
                    catch (Exception)
                    {
                        //todo: Logging
                    }
                }
                return list;
            }
            catch (Exception)
            {
                //todo: Logging
            }
            return null;
        }
        return null;
    }


        protected override IList<MatchingSegmentResult> ListMatchingSegments(ContentReference parentLink, string urlSegment)
        {
            var list = new List<MatchingSegmentResult>();
            foreach (var child in LoadChildren<IContent>(parentLink, LanguageSelector.Fallback("en", true), -1, -1))
            {
                var routable = child as Holmen.Externweb.Web.EpiPageTypes.HolmenGroup.Press.NewsPressReleaseReportsBase;
                var isMatch = routable != null && urlSegment.Equals(routable.URLSegment, StringComparison.OrdinalIgnoreCase);

                if (isMatch)
                {
                    list.Add(new MatchingSegmentResult
                    {
                        ContentLink = child.ContentLink                        
                    });
                }
            }
            return list;
        }


        #endregion

        #region Private methods
        private string CacheKey
        {
            get
            {
                return this.Name;
            }
        }

        #endregion

        #region properties

        public XDocument XmlPages
        {
            get
            {

                var pages = CacheManager.Get(CacheKey) as XDocument;

                if (pages == null)
                {
                    try
                    {
                        pages = XDocument.Load(HttpUtility.UrlDecode(_filePath), LoadOptions.PreserveWhitespace);
                    }
                    catch (Exception)
                    {
                         //todo handle
                    }

                CacheManager.Insert(
                    CacheKey,
                    pages);
                }
                return pages;
            }
        }

        #endregion

        #region cache
        /// <summary>
        /// The set cache settings.
        /// </summary>
        /// <param name="content">
        /// The content.
        /// </param>
        /// <param name="cacheSettings">
        /// The cache settings.
        /// </param>
        protected override void SetCacheSettings(IContent content, CacheSettings cacheSettings)
        {
            if (content == null || cacheSettings == null)
            {
                return;
            }

            // Make the cache of this content provider depend on the original content
            cacheSettings.CacheKeys.Add(_cacheCreator.CreateCommonCacheKey(new ContentReference(content.ContentLink.ID)));
        }

        protected override void SetCacheSettings(ContentReference contentReference, IEnumerable<GetChildrenReferenceResult> children, CacheSettings cacheSettings)
        {
            // Set a low cache setting so new items are fetched from data source, but keep the
            // items already fetched for a long time in the cache.
            cacheSettings.SlidingExpiration = TimeSpan.FromSeconds(120);

            base.SetCacheSettings(contentReference, children, cacheSettings);
        }

        #endregion

    }

    public class RSSPage
    {
        public string Guid { get; set; }
        public string Title { get; set; }
        public string Description { get; set; }
        public string Content { get; set; }
        public DateTime PubDate { get; set; }
        public string Language { get; set; }
        public string DocumentUrl { get; set; }
    }

    public static class Extensions
    {
        public static T GetValue<T>(this XElement element, string name)
        {

            if (element.Element(name) == null)
            {
                return default(T);
            }

            try
            {
                return (T)Convert.ChangeType(element.Element(name).Value, typeof(T));
            }
            catch (Exception)
            {
                return default(T);
            }

        }
        public static T GetAttributeFromElement<T>(this XElement element, string elementName, string attributeName)
        {

            if (element.Element(elementName) == null)
            {
                return default(T);
            }

            try
            {
                if (element.Element(elementName).HasAttributes && element.Element(elementName).Attribute(attributeName) != null)
                {
                }
                return (T)Convert.ChangeType(element.Element(elementName).Attribute(attributeName).Value, typeof(T));
            }
            catch (Exception)
            {
                return default(T);
            }

        }
    }

}

Find the code also on gist github: https://gist.github.com/LucGosso/

This blogpost is a continuation of a series of blog posts on Content Providers, former Page Provider for EPiServer:

Contentprovider example for #EPiServer, Former PageProvider, Part one

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