​​XML数据读取方式性能比较（一）​​

Posted on 2010-08-12 06:33

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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

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：

　　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。