反序列化的性能(Deserialization Performance)

反序列化xml配置文件到一个实体类，和直接读取xml到实体类相比，效率对比相当大，我简单测试了一下，各自占用的时间如下：

部分测试代码：

class Program

{

    static void Main ( string[] args )

    {

        System.Diagnostics.Stopwatch sw1 = new System.Diagnostics.Stopwatch ();

        sw1.Start ();

        Config cfg = LoadConfig_Xml ( "MyTest.config" );

        sw1.Stop ();

        if ( cfg != null )

            Console.WriteLine ( "NormalReader: " + sw1.ElapsedMilliseconds + " ms" );

        sw1.Reset ();

        sw1.Start ();

        cfg = LoadConfig_Deserialize ( "MyTest.config" );

        sw1.Stop ();

        if ( cfg != null )

            Console.WriteLine ( "Deserialize: " + sw1.ElapsedMilliseconds + " ms" );

        Console.Read ();

    }

    public static Config LoadConfig_Deserialize ( string file )

    {

        if ( !System.IO.File.Exists ( file ) ) return null;

        XmlSerializer xs = new XmlSerializer ( typeof ( Config ) );

        using ( StreamReader sr = new StreamReader ( file ) )

        {

            return xs.Deserialize ( sr ) as Config;

        }

    }

    public static Config LoadConfig_Xml ( string file )

    {

        if ( !System.IO.File.Exists ( file ) ) return null;

        try

        {

            XmlDocument doc = new XmlDocument ();

            doc.Load ( file );

            if ( doc == null ) return null;

            XmlNode parent = doc.SelectSingleNode ( @"//Config" );

            if ( parent == null ) return null;

            Config cfg = new Config ();

            foreach ( XmlNode node in parent.ChildNodes )

            {

                if ( node.Name == "MyBooleanAttribute1" )

                    cfg.MyBooleanAttribute1 = Convert.ToBoolean ( node.InnerText );

                if ( node.Name == "MyAttribute2" )

                    cfg.MyAttribute2 = node.InnerText;

                if ( node.Name == "MyBooleanAttribute3" )

                    cfg.MyBooleanAttribute3 = Convert.ToBoolean ( node.InnerText );

                if ( node.Name == "CachedFileList" )

                {

                    if ( node.ChildNodes.Count > 0 )

                    {

                        cfg.CachedFileList = new CachedFileList ();

                        foreach ( XmlNode child in node.ChildNodes )

                        {

                            cfg.CachedFileList.Add ( new CachedFile ( child.Attributes["FileLocation"].InnerText,

                                child.Attributes["FileName"].InnerText, child.Attributes["FileFormat"].InnerText, 

                                Convert.ToInt64 ( child.Attributes["FileChecksum"].InnerText ) ) );

                        }

                    }

                }

            }

            return cfg;

        }

        catch { return null; }

    }

}

Config类定义：

using System;

using System.Collections.Generic;

using System.Text;

using System.Xml;

using System.Xml.Serialization;

using System.IO;

[Serializable]

public class Config

{

    private bool myBooleanAttribute1 = true;

    public bool MyBooleanAttribute1 { get { return myBooleanAttribute1; } set { myBooleanAttribute1 = value; } }

    private string myAttribute2 = "";

    public string MyAttribute2 { get { return myAttribute2; } set { myAttribute2 = value; } }

    private bool myBooleanAttribute3 = true;

    public bool MyBooleanAttribute3 { get { return myBooleanAttribute3; } set { myBooleanAttribute3 = value; } }

    private CachedFileList cachedFileList = new CachedFileList ();

    public CachedFileList CachedFileList

    {

        get { return cachedFileList; }

        set { cachedFileList = value; }

    }

}

[Serializable]

public class CachedFileList : List<CachedFile>

{

}

public class CachedFile

{

    private string fileLocation = "";

    private string fileName = "";

    private string fileFormat = "";

    private long fileChecksum = 0;

    [XmlAttribute ( "FileLocation" )]

    public string FileLocation { get { return fileLocation; } set { fileLocation = value; } }

    [XmlAttribute ( "FileName" )]

    public string FileName { get { return fileName; } set { fileName = value; } }

    [XmlAttribute ( "FileFormat" )]

    public string FileFormat { get { return fileFormat; } set { fileFormat = value; } }

    [XmlAttribute ( "FileChecksum" )]

    public long FileChecksum { get { return fileChecksum; } set { fileChecksum = value; } }

    public CachedFile ( string location, string name, string format, long checksum )

        :this()

    {

        this.fileLocation = location;

        this.fileName = name;

        this.fileFormat = format;

        this.fileChecksum = checksum;

    }

    public CachedFile ()

    {

    }

}

由此可见，反序列化的性能很差，占用时间非常大。在简洁代码的背后是效率的代价。应该根据需要按需选择。

使用XSD安全装载XML并反序列化

如果有XML Schema，就是XSD的情况下，可以首先装载XSD，然后读取XML会比较快；尤其是读取大型XML文件（比如几M）。而且类型安全。

最后再反序列化到实体类。以下是一个例子：

private XmlReader GetValidatingReader(string filePath)

{

    Stream stream = Assembly.GetExecutingAssembly().GetManifestResourceStream("MySchema.xsd");

    XmlTextReader schemaReader = new XmlTextReader(stream);

    stream.Dispose();

    XmlReaderSettings settings = new XmlReaderSettings();

    settings.Schemas.Add("http://schemas.microsoft.com/pag/mynamespacefile", schemaReader);

    XmlReader settingReader = XmlReader.Create(filePath, settings);

    return settingReader;

}

private Config ReadConfig (string configPath)

{

    try

    {

        XmlSerializer serializer = new XmlSerializer ( typeof ( Config ) );

        using ( XmlReader reader = GetValidatingReader () )

        {

           return (Config)serializer.Deserialize ( reader );

        }

    }

    catch ( Exception ex )

    {

        throw new ConfigReaderException ( String.Format (

                                         CultureInfo.CurrentCulture,

                                         Resources.ErrorReadingConfig,

                                         configPath ), ex );

    }

}

Links:

Dataset的序列化传输，压缩和反序列化

如何由XSD自动生成XML和实体类

[转]使用XMLSerializer类持久化数据