标签：blog 结构 压缩 typename sch tput 编码 例子 model
对于WCF应用来说，传输前压缩请求消息和回复消息，不但可以降低网络流量，也可以提高网络传输的性能
一、消息压缩方案
二、用于数据压缩与解压缩组件
三、用于消息压缩与解压的组件
四、用于对请求/回复消息压缩和解压缩的组件
五、将CompressionMessageFormatter用于WCF运行时框架的操作行为
六、查看结构压缩后的消息
七、扩展
一、消息压缩方案
消息压缩在WCF中的实现其实很简单，我们只需要在消息（请求消息/回复消息）被序列化之后，发送之前进行压缩；在接收之后，反序列化之前进行解压缩即可。针对压缩/解压缩使用的时机，有三种典型的解决方案。通过自定义MessageEncoder和MessageEncodingBindingElement 来完成。
1.将编码后的字节流压缩传输
2.创建用于压缩和解压缩的信道
3. 自定义MessageFormatter实现序列化后的压缩和法序列化前的解压缩
这里要介绍的解决方案3。
二、用于数据压缩与解压缩组件
我们支持两种方式的压缩，Dflate和GZip。两种不同的压缩算法通过如下定义的CompressionAlgorithm枚举表示。
1 public enum CompressionAlgorithm 2 { 3 GZip, 4 Deflate 5 }
而如下定义的DataCompressor负责基于上述两种压缩算法实际上的压缩和解压缩工作。
1 internal class DataCompressor 2 { 3 public static byte[] Compress(byte[] decompressedData, CompressionAlgorithm algorithm) 4 { 5 using (MemoryStream stream = new MemoryStream()) 6 { 7 if (algorithm == CompressionAlgorithm.Deflate) 8 { 9 GZipStream stream2 = new GZipStream(stream, CompressionMode.Compress, true); 10 stream2.Write(decompressedData, 0, decompressedData.Length); 11 stream2.Close(); 12 } 13 else 14 { 15 DeflateStream stream3 = new DeflateStream(stream, CompressionMode.Compress, true); 16 stream3.Write(decompressedData, 0, decompressedData.Length); 17 stream3.Close(); 18 } 19 return stream.ToArray(); 20 } 21 } 22 23 public static byte[] Decompress(byte[] compressedData, CompressionAlgorithm algorithm) 24 { 25 using (MemoryStream stream = new MemoryStream(compressedData)) 26 { 27 if (algorithm == CompressionAlgorithm.Deflate) 28 { 29 using (GZipStream stream2 = new GZipStream(stream, CompressionMode.Decompress)) 30 { 31 return LoadToBuffer(stream2); 32 } 33 } 34 else 35 { 36 using (DeflateStream stream3 = new DeflateStream(stream, CompressionMode.Decompress)) 37 { 38 return LoadToBuffer(stream3); 39 } 40 } 41 } 42 } 43 44 private static byte[] LoadToBuffer(Stream stream) 45 { 46 using (MemoryStream stream2 = new MemoryStream()) 47 { 48 int num; 49 byte[] buffer = new byte[0x400]; 50 while ((num = stream.Read(buffer, 0, buffer.Length)) > 0) 51 { 52 stream2.Write(buffer, 0, num); 53 } 54 return stream2.ToArray(); 55 } 56 } 57 }
三、用于消息压缩与解压的组件
而针对消息的压缩和解压缩通过如下一个MessageCompressor来完成。具体来说，我们通过上面定义的DataCompressor对消息的主体部分内容进行压缩，并将压缩后的内容存放到一个预定义的XML元素中（名称和命名空间分别为CompressedBody和http://www.yswenli.net/comporession/），同时添加相应的MessageHeader表示消息经过了压缩，以及采用的压缩算法。对于解压缩，则是通过消息是否具有相应的MessageHeader判断该消息是否经过压缩，如果是则根据相应的算法对其进行解压缩。
具体的实现如下：
1 public class MessageCompressor 2 { 3 public MessageCompressor(CompressionAlgorithm algorithm) 4 { 5 this.Algorithm = algorithm; 6 } 7 public Message CompressMessage(Message sourceMessage) 8 { 9 byte[] buffer; 10 using (XmlDictionaryReader reader1 = sourceMessage.GetReaderAtBodyContents()) 11 { 12 buffer = Encoding.UTF8.GetBytes(reader1.ReadOuterXml()); 13 } 14 if (buffer.Length == 0) 15 { 16 Message emptyMessage = Message.CreateMessage(sourceMessage.Version, (string)null); 17 sourceMessage.Headers.CopyHeadersFrom(sourceMessage); 18 sourceMessage.Properties.CopyProperties(sourceMessage.Properties); 19 emptyMessage.Close(); 20 return emptyMessage; 21 } 22 byte[] compressedData = DataCompressor.Compress(buffer, this.Algorithm); 23 string copressedBody = CompressionUtil.CreateCompressedBody(compressedData); 24 XmlTextReader reader = new XmlTextReader(new StringReader(copressedBody), new NameTable()); 25 Message message2 = Message.CreateMessage(sourceMessage.Version, null, (XmlReader)reader); 26 message2.Headers.CopyHeadersFrom(sourceMessage); 27 message2.Properties.CopyProperties(sourceMessage.Properties); 28 message2.AddCompressionHeader(this.Algorithm); 29 sourceMessage.Close(); 30 return message2; 31 } 32 33 public Message DecompressMessage(Message sourceMessage) 34 { 35 if (!sourceMessage.IsCompressed()) 36 { 37 return sourceMessage; 38 } 39 CompressionAlgorithm algorithm = sourceMessage.GetCompressionAlgorithm(); 40 sourceMessage.RemoveCompressionHeader(); 41 byte[] compressedBody = sourceMessage.GetCompressedBody(); 42 byte[] decompressedBody = DataCompressor.Decompress(compressedBody, algorithm); 43 string newMessageXml = Encoding.UTF8.GetString(decompressedBody); 44 XmlTextReader reader2 = new XmlTextReader(new StringReader(newMessageXml)); 45 Message newMessage = Message.CreateMessage(sourceMessage.Version, null, reader2); 46 newMessage.Headers.CopyHeadersFrom(sourceMessage); 47 newMessage.Properties.CopyProperties(sourceMessage.Properties); 48 return newMessage; 49 } 50 public CompressionAlgorithm Algorithm { get; private set; } 51 }
下面是针对Message类型而定义了一些扩展方法和辅助方法。
1 public static class CompressionUtil 2 { 3 public const string CompressionMessageHeader = "Compression"; 4 public const string CompressionMessageBody = "CompressedBody"; 5 public const string Namespace = "http://www.yswenli.net/compression"; 6 7 public static bool IsCompressed(this Message message) 8 { 9 return message.Headers.FindHeader(CompressionMessageHeader, Namespace) > -1; 10 } 11 12 public static void AddCompressionHeader(this Message message, CompressionAlgorithm algorithm) 13 { 14 message.Headers.Add(MessageHeader.CreateHeader(CompressionMessageHeader, Namespace, string.Format("algorithm = \"{0}\"", algorithm))); 15 } 16 17 public static void RemoveCompressionHeader(this Message message) 18 { 19 message.Headers.RemoveAll(CompressionMessageHeader, Namespace); 20 } 21 22 public static CompressionAlgorithm GetCompressionAlgorithm(this Message message) 23 { 24 if (message.IsCompressed()) 25 { 26 var algorithm = message.Headers.GetHeader<string>(CompressionMessageHeader, Namespace); 27 algorithm = algorithm.Replace("algorithm =", string.Empty).Replace("\"", string.Empty).Trim(); 28 if (algorithm == CompressionAlgorithm.Deflate.ToString()) 29 { 30 return CompressionAlgorithm.Deflate; 31 } 32 33 if (algorithm == CompressionAlgorithm.GZip.ToString()) 34 { 35 return CompressionAlgorithm.GZip; 36 } 37 throw new InvalidOperationException("Invalid compression algrorithm!"); 38 } 39 throw new InvalidOperationException("Message is not compressed!"); 40 } 41 42 public static byte[] GetCompressedBody(this Message message) 43 { 44 byte[] buffer; 45 using (XmlReader reader1 = message.GetReaderAtBodyContents()) 46 { 47 buffer = Convert.FromBase64String(reader1.ReadElementString(CompressionMessageBody, Namespace)); 48 } 49 return buffer; 50 } 51 52 public static string CreateCompressedBody(byte[] content) 53 { 54 StringWriter output = new StringWriter(); 55 using (XmlWriter writer2 = XmlWriter.Create(output)) 56 { 57 writer2.WriteStartElement(CompressionMessageBody, Namespace); 58 writer2.WriteBase64(content, 0, content.Length); 59 writer2.WriteEndElement(); 60 } 61 return output.ToString(); 62 } 63 }
四、用于对请求/回复消息压缩和解压缩的组件
消息的序列化和反序列化最终是通过MessageFormatter来完成的。具体来说，客户端通过ClientMessageFormatter实现对请求消息的序列化和对回复消息的序列化，而服务端通过DispatchMessageFormatter实现对请求消息的反序列化和对回复消息的序列化。
在默认的情况下，WCF选用的MessageFormatter为DataContractSerializerOperationFormatter，它采用DataContractSerializer进行实际的序列化和法序列化操作。我们自定义的MessageFormatter实际上是对DataContractSerializerOperationFormatter的封装，我们依然使用它来完成序列化和反序列化工作，额外实现序列化后的压缩和法序列化前的解压缩。
因为DataContractSerializerOperationFormatter是一个internal类型，我们只有通过反射的方式来创建它。如下的代码片断为用于进行消息压缩与解压缩的自定义MessageFormatter，即CompressionMessageFormatter的定义。
1 public class CompressionMessageFormatter : IDispatchMessageFormatter, IClientMessageFormatter 2 { 3 private const string DataContractSerializerOperationFormatterTypeName = "System.ServiceModel.Dispatcher.DataContractSerializerOperationFormatter, System.ServiceModel, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"; 4 5 public IDispatchMessageFormatter InnerDispatchMessageFormatter { get; private set; } 6 public IClientMessageFormatter InnerClientMessageFormatter { get; private set; } 7 public MessageCompressor MessageCompressor { get; private set; } 8 9 public CompressionMessageFormatter(CompressionAlgorithm algorithm, OperationDescription description, DataContractFormatAttribute dataContractFormatAttribute, DataContractSerializerOperationBehavior serializerFactory) 10 { 11 this.MessageCompressor = new MessageCompressor(algorithm); 12 Type innerFormatterType = Type.GetType(DataContractSerializerOperationFormatterTypeName); 13 var innerFormatter = Activator.CreateInstance(innerFormatterType, description, dataContractFormatAttribute, serializerFactory); 14 this.InnerClientMessageFormatter = innerFormatter as IClientMessageFormatter; 15 this.InnerDispatchMessageFormatter = innerFormatter as IDispatchMessageFormatter; 16 } 17 18 public void DeserializeRequest(Message message, object[] parameters) 19 { 20 message = this.MessageCompressor.DecompressMessage(message); 21 this.InnerDispatchMessageFormatter.DeserializeRequest(message, parameters); 22 } 23 24 public Message SerializeReply(MessageVersion messageVersion, object[] parameters, object result) 25 { 26 var message = this.InnerDispatchMessageFormatter.SerializeReply(messageVersion, parameters, result); 27 return this.MessageCompressor.CompressMessage(message); 28 } 29 30 public object DeserializeReply(Message message, object[] parameters) 31 { 32 message = this.MessageCompressor.DecompressMessage(message); 33 return this.InnerClientMessageFormatter.DeserializeReply(message, parameters); 34 } 35 36 public Message SerializeRequest(MessageVersion messageVersion, object[] parameters) 37 { 38 var message = this.InnerClientMessageFormatter.SerializeRequest(messageVersion, parameters); 39 return this.MessageCompressor.CompressMessage(message); 40 } 41 }
五、将CompressionMessageFormatter用于WCF运行时框架的操作行为
ClientMessageFormatter和DispatchMessageFormatter实际上属于ClientOperation和DispatchOperation的组件。我们可以通过如下一个自定义的操作行为CompressionOperationBehaviorAttribute将其应用到相应的操作上。
1 [AttributeUsage(AttributeTargets.Method)] 2 public class CompressionOperationBehaviorAttribute : Attribute, IOperationBehavior 3 { 4 public CompressionAlgorithm Algorithm { get; set; } 5 6 public void AddBindingParameters(OperationDescription operationDescription, BindingParameterCollection bindingParameters) { } 7 8 public void ApplyClientBehavior(OperationDescription operationDescription, ClientOperation clientOperation) 9 { 10 clientOperation.SerializeRequest = true; 11 clientOperation.DeserializeReply = true; 12 var dataContractFormatAttribute = operationDescription.SyncMethod.GetCustomAttributes(typeof(DataContractFormatAttribute), true).FirstOrDefault() as DataContractFormatAttribute; 13 if (null == dataContractFormatAttribute) 14 { 15 dataContractFormatAttribute = new DataContractFormatAttribute(); 16 } 17 18 var dataContractSerializerOperationBehavior = operationDescription.Behaviors.Find<DataContractSerializerOperationBehavior>(); 19 clientOperation.Formatter = new CompressionMessageFormatter(this.Algorithm, operationDescription, dataContractFormatAttribute, dataContractSerializerOperationBehavior); 20 } 21 22 public void ApplyDispatchBehavior(OperationDescription operationDescription, DispatchOperation dispatchOperation) 23 { 24 dispatchOperation.SerializeReply = true; 25 dispatchOperation.DeserializeRequest = true; 26 var dataContractFormatAttribute = operationDescription.SyncMethod.GetCustomAttributes(typeof(DataContractFormatAttribute), true).FirstOrDefault() as DataContractFormatAttribute; 27 if (null == dataContractFormatAttribute) 28 { 29 dataContractFormatAttribute = new DataContractFormatAttribute(); 30 } 31 var dataContractSerializerOperationBehavior = operationDescription.Behaviors.Find<DataContractSerializerOperationBehavior>(); 32 dispatchOperation.Formatter = new CompressionMessageFormatter(this.Algorithm, operationDescription, dataContractFormatAttribute, dataContractSerializerOperationBehavior); 33 } 34 35 public void Validate(OperationDescription operationDescription) { } 36 }
六、查看结构压缩后的消息
为了验证应用了CompressionOperationBehaviorAttribute特性的操作方法对应的消息是否经过了压缩，我们可以通过一个简单的例子来检验。我们采用常用的计算服务的例子，下面是服务契约和服务类型的定义。我们上面定义的CompressionOperationBehaviorAttribute应用到服务契约的Add操作上。
1 [ServiceContract(Namespace = "http://www.yswenli.net/")] 2 public interface ICalculator 3 { 4 [OperationContract] 5 [CompressionOperationBehavior] 6 double Add(double x, double y); 7 } 8 public class CalculatorService : ICalculator 9 { 10 public double Add(double x, double y) 11 { 12 return x + y; 13 } 14 }
我们采用BasicHttpBinding作为终结点的绑定类型（具体的配置请查看源代码），下面是通过Fiddler获取的消息的内容，它们的主体部分都经过了基于压缩的编码。
1 <s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/"> 2 <s:Header> 3 <Compression xmlns="http://www.yswenli.net/compression">algorithm = "GZip"</Compression> 4 </s:Header> 5 <s:Body> 6 <CompressedBody xmlns="http://www.yswenli.net/compression">7L0HYBx ... CQAA//8=</CompressedBody> 7 </s:Body> 8 </s:Envelope>
回复消息
1 <s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/"> 2 <s:Header> 3 <Compression xmlns="http://www.yswenli.net/compression">algorithm = "GZip"</Compression> 4 </s:Header> 5 <s:Body> 6 <CompressedBody xmlns="http://www.yswenli.net/compression">7L0H...PAAAA//8=</CompressedBody> 7 </s:Body> 8 </s:Envelope>
七、扩展
如果不想使微软自带的序列化或者因为某些原因（emoji字符异常等）可以使用自定义的IDispatchMessageInspector。由于CompressionMessageFormatter使用基于DataContractSerializer序列化器的DataContractSerializerOperationFormatter进行消息的序列化和发序列化工作，而DataContractSerializer仅仅是WCF用于序列化的一种默认的选择（WCF还可以采用传统的XmlSeriaizer）；为了让CompressionMessageFormatter能够使用其他序列化器，可以对于进行相应的修正。
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标签：blog 结构 压缩 typename sch tput 编码 例子 model
原文地址：http://www.cnblogs.com/yswenli/p/6670081.html
