XML数据读取方式性能比较(一)
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2022-03-05 13:28:30
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几个月来,疑被SOA,一直在和xml操作打交道,SQL差不多又忘光了。现在已经知道,至少有四种常用人XML数据操作方式(好像java差不多),不过还没有实际比较过这些方式各有哪些特点或优劣。正好看到网上也没有这方面的实验,偶来总结一下。
测试开始先读取XML源,用一个比较大的rss文件链接,复制到项目bin/debug目录下。
Stream xmlStream = new MemoryStream(File.ReadAllBytes(path));
一、XmlDocument 方式
代码
1 static IList testXmlDocument() 2 { 3 var doc = new XmlDocument(); 4 doc.Load(xmlStream); 5 var nodeList = doc.DocumentElement.ChildNodes; 6 var lstChannel = new List<Object>(nodeList.Count ); 7 foreach (XmlNode node in nodeList) 8 { 9 var channel = new 10 { 11 Title = node.SelectSingleNode("title").InnerText, 12 Link = node.SelectSingleNode("link").InnerText, 13 Description = node.SelectSingleNode("description").InnerText, 14 Content = node.SelectSingleNode("content").InnerText, 15 PubDate = node.SelectSingleNode("pubDate").InnerText, 16 Author = node.SelectSingleNode("author").InnerText, 17 Category = node.SelectSingleNode("category").InnerText 18 }; 19 lstChannel.Add(channel); 20 } 21 return lstChannel; 22 }
二、XPathNavigator 方式
代码
1 static IList testXmlNavigator() 2 { 3 var doc = new XmlDocument(); 4 doc.Load(xmlStream); 5 var nav = doc.CreateNavigator(); 6 nav.MoveToRoot(); 7 var nodeList = nav.Select("/channel/item"); 8 var lstChannel = new List<Object>(nodeList.Count); 9 foreach (XPathNavigator node in nodeList) 10 { 11 var channel = new 12 { 13 Title = node.SelectSingleNode("title").Value, 14 Link = node.SelectSingleNode("link").Value, 15 Description = node.SelectSingleNode("description").Value, 16 Content = node.SelectSingleNode("content").Value, 17 PubDate = node.SelectSingleNode("pubDate").Value, 18 Author = node.SelectSingleNode("author").Value, 19 Category = node.SelectSingleNode("category").Value 20 }; 21 lstChannel.Add(channel); 22 } 23 return lstChannel; 24 }
三、XmlTextReader 方式
代码
1 static List<Channel> testXmlReader() 2 { 3 var lstChannel = new List<Channel>(); 4 var reader = XmlReader.Create(xmlStream); 5 while (reader.Read()) 6 { 7 if (reader.Name == "item" && reader.NodeType == XmlNodeType.Element) 8 { 9 var channel = new Channel(); 10 lstChannel.Add(channel); 11 while (reader.Read()) 12 { 13 if (reader.Name == "item") break; 14 if (reader.NodeType != XmlNodeType.Element) continue; 15 switch (reader.Name) 16 { 17 case "title": 18 channel.Title = reader.ReadString(); 19 break; 20 case "link": 21 channel.Link = reader.ReadString(); 22 break; 23 case "description": 24 channel.Description = reader.ReadString(); 25 break; 26 case "content": 27 channel.Content = reader.ReadString(); 28 break; 29 case "pubDate": 30 channel.PubDate = reader.ReadString(); 31 break; 32 case "author": 33 channel.Author = reader.ReadString(); 34 break; 35 case "category": 36 channel.Category = reader.ReadString(); 37 break; 38 default: 39 break; 40 } 41 } 42 } 43 } 44 return lstChannel; 45 }
四、Linq to XML 方式
代码
1 static IList testXmlLinq() 2 { 3 var xd = XDocument.Load(xmlStream); 4 var list = from node in xd.Elements("channel").Descendants("item") 5 select new 6 { 7 Title = node.Element("title").Value, 8 Link = node.Element("link").Value, 9 Description = node.Element("description").Value, 10 Content = node.Element("content").Value, 11 PubDate = node.Element("pubDate").Value, 12 Author = node.Element("author").Value, 13 Category = node.Element("category").Value 14 }; 15 return list.ToList(); 16 }
测试结果:
XmlDocment 47ms XPathNavigator 42ms XmlTextReader 23ms Xml Linq 28ms
小结一下自己的认识,XmlDocument的操作基本按W3C的DOM操作方式,不过要将全部节点解析成对象加载到内存中,往往造成很大浪费。所以微软自己的编程规范也不推荐用它。这里由于读取了所有节点,可能因此性能和Navigator方式相差不大。在三种随机读取方式中,Xml Linq性能最高,只是方法名有点别扭。XmlTextReader方式是所谓的SAX,只读向前,无疑性能最高,不过实现上麻烦了不少,要比较精确的控制访问逻辑,也无法用匿名类存储数据。
.Net 3.5发布Xml Linq可以很好地取代前两种方式,通常情况下,最好用它。只有个别场合,如果对性能要求极高,或者读取Xml数据量太大不能一下子下载或读取到内存中,那就只好痛苦委身于XmlTextReader了。
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