【原创】RSS开发心得小结

几经面试和简历更新，发现自己做了这么久的开发，却少于做总结，一个个项目过去了，但是知识的累积沉淀却很少……

借着这次机会，把以前的skill整理一下，浓缩的才是精华。为自己也为其他初学的朋友做个参考。

RSS（全称Really Simple Syndication） 目前广泛用于网上新闻频道，blog和wiki，主要的版本有0.91, 1.0, 2.0。

另外还有Google制定的ATOM格式，以及作为Feed集合的OPML文件。

最常见的Feed格式是Rss1.0,2.0和ATOM，解析时通过不同的命名空间来处理不同的版本，下面是解析的主要代码：

        /// <summary>
        /// 根据xml内容解析Feed
        /// </summary>
        /// <param name="url">Feed源地址</param>
        /// <param name="xmlContent">Feed xml 内容</param>
        /// <returns>返回解析后的Feed对象实例</returns>
        public static Feed AnalyseFeedContent(string url, string xmlContent)
        {            
            Feed feed = new Feed();
            feed.Url = url;
            feed.ChannelInfo = new FeedChannel();

            XmlDocument doc = new XmlDocument();
            doc = ReadGlobals.LoadXml(doc, xmlContent, url);

            // 添加常用的命名空间
            XmlNamespaceManager mgr = new XmlNamespaceManager(doc.NameTable);
            mgr.AddNamespace("rdf", "http://purl.org/rss/1.0/");
            mgr.AddNamespace("content", "http://purl.org/rss/1.0/modules/content/");
            mgr.AddNamespace("dc", "http://purl.org/dc/elements/1.1/");
            XmlNode nodeRoot = doc.DocumentElement;
            XmlNode nodeChannel;
            XmlNodeList nodeList;

            try
            {
                if (nodeRoot != null)
                {
                    // enclosure地址
                    if (nodeRoot.Attributes["xmlns:enc"] != null)
                    {
                        mgr.AddNamespace("enc", nodeRoot.Attributes["xmlns:enc"].Value);     
                    }
                    else
                    {
                        mgr.AddNamespace("enc", "http://crocodile.org/ns/rss/2.0/enclosures");
                    }

                    // trackback地址
                    if (nodeRoot.Attributes["xmlns:trackback"] != null)
                    {
                        mgr.AddNamespace("trackback", nodeRoot.Attributes["xmlns:trackback"].Value);
                    }
                    else
                    {
                        mgr.AddNamespace("trackback", "http://madskills.com/public/xml/rss/module/trackback/");
                    }

                    if (nodeRoot.Name.ToLower() == "opml")
                    {
                        // 是opml文件
                        feed.Type = FeedType.OPML;
                    }

                    if (nodeRoot.Name.ToLower() == "feed")
                    {
                        // 是atom文件
                        feed.Type = FeedType.ATOM_0_3;

                        string strAtomNameSpace = "http://www.w3.org/2005/Atom";
                        // 以头部的命名空间为准;
                        if (nodeRoot.Attributes["xmlns"] != null)
                        {
                            strAtomNameSpace = nodeRoot.Attributes["xmlns"].Value;
                        }                        
                        mgr.AddNamespace("atom", strAtomNameSpace);

                        feed.ChannelInfo = GetChannel(doc, mgr, "atom");

                        nodeList = doc.SelectNodes("//atom:entry", mgr);
                        feed.Items = GetItems(nodeList, feed.Type, mgr);
                    }

                    if (nodeRoot.Name.ToLower() == "rdf:rdf")
                    {
                        // 是rss1.0文件  
                        feed.Type = FeedType.RSS_1_0;
                        feed.ChannelInfo = GetChannel(doc, mgr, "rdf");

                        nodeList = doc.SelectNodes("//rdf:item", mgr);
                        feed.Items = GetItems(nodeList, feed.Type, mgr);
                    }

                    if (nodeRoot.Name.ToLower() == "rss")
                    {
                        // 是rss2.0文件
                        feed.Type = FeedType.RSS_2_0;

                        nodeChannel = doc.SelectSingleNode("rss/channel");
                        feed.ChannelInfo = GetChannelForRss20(nodeChannel);                      

                        nodeList = nodeChannel.SelectNodes("item", mgr);
                        feed.Items = GetItems(nodeList, feed.Type, mgr);
                    }
                }
            }
            catch (Exception ex)
            {
                Log.Write(ex);
            }

            return feed;
        }

 Feed主要分为两部分，Channel和ItemList部分，分别用如下方法解析：

        /// <summary>
        /// 获取　FeedChannel 数据
        /// </summary>
        private static FeedChannel GetChannel(XmlDocument xdtDoc, XmlNamespaceManager mgr, string prefix)
        {
            FeedChannel channel = new FeedChannel();

            if (xdtDoc != null)
            {
                string title = string.Empty, generator = string.Empty, link = string.Empty, description = string.Empty, language = string.Empty;
                string managingeditor = string.Empty, webmaster = string.Empty, copyright = string.Empty, pubdate = string.Empty, lastbuilddate = string.Empty;

                string strPrefix = prefix;

                XmlNode xneLogo = xdtDoc.SelectSingleNode("//" + strPrefix + ":logo", mgr);
                if (xneLogo != null)
                {
                    channel.Logo.Src = xneLogo.InnerText;
                }

                XmlNode snTitle = xdtDoc.SelectSingleNode("//" + strPrefix + ":title", mgr);
                if (snTitle != null)
                {
                    channel.Title = snTitle.InnerText;
                }
                
                XmlNode snLink = xdtDoc.SelectSingleNode("//" + strPrefix + ":link[@rel='alternate']/@href", mgr);
                if (snLink != null)
                {
                    channel.Link = snLink.InnerText;
                }
                else
                {
                    channel.Link = xdtDoc.SelectSingleNode("//" + strPrefix + ":link", mgr) == null ? string.Empty : xdtDoc.SelectSingleNode("//" + strPrefix + ":link", mgr).InnerText;
                }


                XmlNode snDescription = xdtDoc.SelectSingleNode("//" + strPrefix + ":tagline", mgr);
                if (snDescription != null)
                {
                    channel.Description = snDescription.InnerText;
                }

                XmlNode snLanguage = xdtDoc.SelectSingleNode("//" + strPrefix + ":feed/@xml:lang", mgr);
                if (snLanguage != null)
                {
                    try
                    {
                        Thread.CurrentThread.CurrentUICulture = new CultureInfo(snLanguage.InnerText);
                        channel.Language = CultureInfo.CreateSpecificCulture(language).LCID;
                    }
                    catch
                    {
                        channel.Language = 0;
                    }
                }
            }
            return channel;
        }

        /// <summary>
        /// 获取item列表
        /// </summary>
        /// <param name="xnlItems"></param>
        public static List<FeedItem> GetItems(XmlNodeList xnlItems, FeedType type, XmlNamespaceManager mgr)
        {
            List<FeedItem> lstItems = new List<FeedItem>();
            if (xnlItems != null)
            {
                switch (type)
                {
                    case FeedType.RSS_1_0:
                        foreach (XmlNode xne in xnlItems)
                        {
                            FeedItem fim = new FeedItem();
                            fim.Title = xne.SelectSingleNode("rdf:title", mgr) != null ? xne.SelectSingleNode("rdf:title", mgr).InnerText : string.Empty;
                            fim.Link = xne.SelectSingleNode("rdf:link", mgr) != null ? xne.SelectSingleNode("rdf:link", mgr).InnerText : string.Empty;
                            //rim.Description = xne.SelectSingleNode("rdf:description", mgr) != null ? xne.SelectSingleNode("rdf:description", mgr).InnerText : string.Empty;
                            string strContent = xne.SelectSingleNode("content:encoded", mgr) != null ? xne.SelectSingleNode("content:encoded", mgr).InnerText : string.Empty;
                            string strDescription = xne.SelectSingleNode("rdf:description", mgr) != null ? xne.SelectSingleNode("rdf:description", mgr).InnerText : string.Empty;
                            fim.Description = strContent == string.Empty ? strDescription : strContent;
                            fim.Description = fim.Description.Replace("<![CDATA[", string.Empty).Replace("]]>", string.Empty);
                            string strAuthorName = xne.SelectSingleNode("//rdf:author", mgr) != null ? xne.SelectSingleNode("//rdf:author", mgr).InnerText : string.Empty;
                            if (strAuthorName != string.Empty)
                            {
                                strAuthorName = xne.SelectSingleNode("dc:creator", mgr) != null ? xne.SelectSingleNode("dc:creator", mgr).InnerText : string.Empty;
                            }
                            if (strAuthorName != string.Empty)
                            {
                                fim.Author = new FeedPerson();
                                fim.Author.Name = strAuthorName;
                            }
                            fim.PubDate = xne.SelectSingleNode("rdf:pubDate", mgr) != null ? GetDateTimeByUrl(fim.Link,xne.SelectSingleNode("rdf:pubDate", mgr).InnerText) : DateTime.MinValue;
                            if (fim.PubDate == DateTime.MinValue)
                            {
                                fim.PubDate = xne.SelectSingleNode("dc:date", mgr) != null ? GetDateTimeByUrl(fim.Link, xne.SelectSingleNode("dc:date", mgr).InnerText) : DateTime.MinValue;
                            }
                            XmlNodeList xnlSubjects = xne.SelectNodes("dc:subject", mgr);
                            if (xnlSubjects != null)
                            {
                                foreach (XmlNode xnlSubject in xnlSubjects)
                                {
                                    fim.Subject += xnlSubject.InnerText + ",";
                                }
                            }
                            XmlNode xndEnclosure = xne.SelectSingleNode("enclosure", mgr);
                            if (xndEnclosure != null)
                            {
                                fim.Enclosures = new List<FeedEnclosure>();
                                FeedEnclosure enc = new FeedEnclosure();
                                enc.Type = xndEnclosure.Attributes["type"] != null ? xndEnclosure.Attributes["type"].Value : string.Empty;
                                string strLength = xndEnclosure.Attributes["length"] != null ? xndEnclosure.Attributes["length"].Value : string.Empty;
                                try
                                {
                                    enc.Length = Convert.ToInt32(strLength);
                                }
                                catch { }
                                enc.Url = xndEnclosure.Attributes["url"] != null ? xndEnclosure.Attributes["url"].Value : string.Empty;
                                fim.Enclosures.Add(enc);
                            }
                            fim.Description += GetHtmlByByEnclosure(fim.Enclosures);
                            fim.TrackbackPing = xne.SelectSingleNode("trackback:ping", mgr) != null ? xne.SelectSingleNode("trackback:ping", mgr).InnerText : string.Empty;
                            lstItems.Add(fim);
                        }
                        break;
                    case FeedType.RSS_2_0:
                        foreach (XmlNode xne in xnlItems)
                        {
                            FeedItem fim = new FeedItem();
                            fim.Title = xne.SelectSingleNode("title", mgr) != null ? xne.SelectSingleNode("title", mgr).InnerText : string.Empty;
                            fim.Link = xne.SelectSingleNode("link", mgr) != null ? xne.SelectSingleNode("link", mgr).InnerText : string.Empty;
                            string strContent = xne.SelectSingleNode("content:encoded", mgr) != null ? xne.SelectSingleNode("content:encoded", mgr).InnerText : string.Empty;
                            string strDescription = xne.SelectSingleNode("description", mgr) != null ? xne.SelectSingleNode("description", mgr).InnerText : string.Empty;
                            fim.Description = strContent == string.Empty ? strDescription : strContent;
                            fim.Description = fim.Description.Replace("<![CDATA[", string.Empty).Replace("]]>", string.Empty);
                            string strAuthorName = xne.SelectSingleNode("author", mgr) != null ? xne.SelectSingleNode("author", mgr).InnerText : string.Empty;
                            if (strAuthorName != string.Empty)
                            {
                                strAuthorName = xne.SelectSingleNode("dc:creator", mgr) != null ? xne.SelectSingleNode("dc:creator", mgr).InnerText : string.Empty;
                            }
                            if (strAuthorName != string.Empty)
                            {
                                fim.Author = new FeedPerson();
                                fim.Author.Name = strAuthorName;
                            }
                            fim.PubDate = xne.SelectSingleNode("pubDate", mgr) != null ? GetDateTimeByUrl(fim.Link,xne.SelectSingleNode("pubDate", mgr).InnerText) : DateTime.MinValue;
                            if (fim.PubDate == DateTime.MinValue)
                            {
                                fim.PubDate = xne.SelectSingleNode("dc:date", mgr) != null ? GetDateTimeByUrl(fim.Link,xne.SelectSingleNode("dc:date", mgr).InnerText) : DateTime.MinValue;
                            }
                            fim.Guid = xne.SelectSingleNode("guid", mgr) != null ? xne.SelectSingleNode("guid", mgr).InnerText : string.Empty;
                            XmlNodeList xnlSubjects = xne.SelectNodes("dc:subject", mgr);
                            if (xnlSubjects != null)
                            {
                                foreach (XmlNode xnlSubject in xnlSubjects)
                                {
                                    fim.Subject += xnlSubject.InnerText + ",";
                                }
                            }                            
                            XmlNodeList xnlCategorys = xne.SelectNodes("category", mgr);
                            if (xnlCategorys != null)
                            {
                                foreach (XmlNode xnlCategory in xnlCategorys)
                                {
                                    fim.Category += xnlCategory != null ? xnlCategory.InnerText : string.Empty;
                                    fim.Category += ",";
                                }
                            }
                            XmlNode xndEnclosure = xne.SelectSingleNode("enclosure", mgr);
                            if (xndEnclosure != null)
                            {
                                fim.Enclosures = new List<FeedEnclosure>();
                                FeedEnclosure enc = new FeedEnclosure();
                                enc.Type = xndEnclosure.Attributes["type"] != null ? xndEnclosure.Attributes["type"].Value : string.Empty;
                                string strLength = xndEnclosure.Attributes["length"] != null ? xndEnclosure.Attributes["length"].Value : string.Empty;
                                try
                                {
                                    enc.Length = Convert.ToInt32(strLength);
                                }
                                catch { }
                                enc.Url = xndEnclosure.Attributes["url"] != null ? xndEnclosure.Attributes["url"].Value : string.Empty;
                                fim.Enclosures.Add(enc);
                            }
                            fim.Description += GetHtmlByByEnclosure(fim.Enclosures);
                            fim.TrackbackPing = xne.SelectSingleNode("trackback:ping", mgr) != null ? xne.SelectSingleNode("trackback:ping", mgr).InnerText : string.Empty;
                            lstItems.Add(fim);
                        }
                        break;
                    case FeedType.ATOM_0_3:

                        foreach (XmlNode xne in xnlItems)
                        {
                            FeedItem fim = new FeedItem();
                            fim.Title = xne.SelectSingleNode("atom:title", mgr) != null ? xne.SelectSingleNode("atom:title", mgr).InnerText : string.Empty;
                            fim.Link = xne.SelectSingleNode("atom:link[@rel='alternate']", mgr) != null ? xne.SelectSingleNode("atom:link[@rel='alternate']", mgr).Attributes["href"].InnerText : string.Empty;
                            fim.Summary = xne.SelectSingleNode("atom:summary", mgr) != null ? xne.SelectSingleNode("atom:summary", mgr).InnerText : string.Empty;
                            fim.Description = xne.SelectSingleNode("atom:content", mgr) != null ? xne.SelectSingleNode("atom:content", mgr).InnerText : string.Empty;
                            fim.Description = fim.Description.Replace("<![CDATA[", string.Empty).Replace("]]>", string.Empty);

                            fim.Guid = xne.SelectSingleNode("atom:id", mgr) != null ? xne.SelectSingleNode("atom:id", mgr).InnerText : string.Empty;
                            fim.Contributor = xne.SelectSingleNode("atom:contributor", mgr) != null ? xne.SelectSingleNode("atom:contributor", mgr).InnerText : string.Empty;
                            XmlNode xneAuthor = xne.SelectSingleNode("atom:author", mgr);
                            if (xneAuthor != null)
                            {
                                fim.Author = new FeedPerson();
                                fim.Author.Name = xneAuthor.SelectSingleNode("atom:name", mgr) != null ? xneAuthor.SelectSingleNode("atom:name", mgr).InnerText : string.Empty;
                                fim.Author.Url = xneAuthor.SelectSingleNode("atom:uri", mgr) != null ? xneAuthor.SelectSingleNode("atom:uri", mgr).InnerText : string.Empty;
                                fim.Author.Email = xneAuthor.SelectSingleNode("atom:email", mgr) != null ? xneAuthor.SelectSingleNode("atom:email", mgr).InnerText : string.Empty;
                            }                            
                            fim.UpdateDate = xne.SelectSingleNode("atom:updated", mgr) != null ? GetDateTimeByUrl(fim.Link, xne.SelectSingleNode("atom:updated", mgr).InnerText) : DateTime.MinValue;
                            if (fim.UpdateDate == DateTime.MinValue)
                            {
                                fim.UpdateDate = xne.SelectSingleNode("atom:modified", mgr) != null ? GetDateTimeByUrl(fim.Link, xne.SelectSingleNode("atom:modified", mgr).InnerText) : DateTime.MinValue;
                            }
                            fim.PubDate = xne.SelectSingleNode("atom:published", mgr) != null ? GetDateTimeByUrl(fim.Link, xne.SelectSingleNode("atom:published", mgr).InnerText) : DateTime.MinValue;
                            if (fim.PubDate == DateTime.MinValue)
                            {
                                fim.PubDate = xne.SelectSingleNode("atom:issued", mgr) != null ? GetDateTimeByUrl(fim.Link, xne.SelectSingleNode("atom:issued", mgr).InnerText) : DateTime.MinValue;
                            }
                            if (fim.PubDate == DateTime.MinValue)
                            {
                                fim.PubDate = xne.SelectSingleNode("atom:created", mgr) != null ? GetDateTimeByUrl(fim.Link, xne.SelectSingleNode("atom:created", mgr).InnerText) : DateTime.MinValue;
                            }
                            XmlNodeList xnlTags = xne.SelectNodes("dc:subject", mgr);
                            XmlNodeList xnlSubjects = xne.SelectNodes("dc:subject", mgr);
                            if (xnlSubjects != null)
                            {
                                foreach (XmlNode xnlSubject in xnlSubjects)
                                {
                                    fim.Subject += xnlSubject.InnerText + ",";
                                }
                            }
                            XmlNodeList xnlCategorys = xne.SelectNodes("atom:category", mgr);
                            if (xnlCategorys != null)
                            {
                                foreach (XmlNode xnlCategory in xnlCategorys)
                                {
                                    fim.Category += xnlCategory.Attributes["term"] != null ? xnlCategory.Attributes["term"].Value : string.Empty;
                                    fim.Category += ",";
                                }
                            }
                            XmlNodeList xnlEnclosures = xne.SelectNodes("atom:link[@rel='enclosure']", mgr);
                            if (xnlEnclosures != null)
                            {
                                fim.Enclosures = new List<FeedEnclosure>();
                                foreach (XmlNode xndEnclosure in xnlEnclosures)
                                {
                                    FeedEnclosure enc = new FeedEnclosure();
                                    enc.Type = xndEnclosure.Attributes["type"] != null ? xndEnclosure.Attributes["type"].Value : string.Empty;
                                    string strLength = xndEnclosure.Attributes["length"] != null ? xndEnclosure.Attributes["length"].Value : string.Empty;
                                    try
                                    {
                                        enc.Length = Convert.ToInt32(strLength);
                                    }
                                    catch { }
                                    enc.Url = xndEnclosure.Attributes["href"] != null ? xndEnclosure.Attributes["href"].Value : string.Empty;
                                    enc.Title = xndEnclosure.Attributes["title"] != null ? xndEnclosure.Attributes["title"].Value : string.Empty;
                                    fim.Enclosures.Add(enc);
                                }
                            }
                            fim.Description += GetHtmlByByEnclosure(fim.Enclosures);
                            fim.TrackbackPing = xne.SelectSingleNode("trackback:ping", mgr) != null ? xne.SelectSingleNode("trackback:ping", mgr).InnerText : string.Empty;
                            fim.Rights = xne.SelectSingleNode("atom:rights", mgr) != null ? xne.SelectSingleNode("atom:rights", mgr).InnerText : string.Empty;
                            lstItems.Add(fim);
                        }
                        break;
                    default:
                        return null;
                }
            }
            return lstItems;

        }