Question

With the help of this question and this post I’ve managed to get WebHttpBinding to work with compression (by means of copy-pasting the code). When pointing the browser to my service method, it downloads a file which I can rename to .zip and decompress, so the compression part works. But I’m not able to use Json instead of XML. When I add the webget attribute to the method I just get “[Fiddler] ReadResponse() failed: The server did not return a response for this request.”

Also the GZipMessageEncoder.WriteMessage isn’t even called. What do I need to change in order to get this working with Json ?

Thanks.

Answer 1

From the post on MSDN, you’d also need to override the MessageEncoder.IsContentTypeSupported to make sure that the gzip encoder also accepts JSON.

The code below has the modified version of that code. I also added a message inspector to add a Content-Encoding header, which will allow the browsers to understand the data as-is.

public class StackOverflow_14602036
{
    [DataContract]
    public class MyDC
    {
        [DataMember]
        public string str;
        [DataMember]
        public int[] intArray;

        public static MyDC CreateLargeInstance(int size)
        {
            Random rndGen = new Random(1);
            StringBuilder sb = new StringBuilder();
            MyDC result = new MyDC();
            for (int i = 0; i < size; i++)
            {
                sb.Append((char)rndGen.Next('a', 'z'));
            }

            result.str = sb.ToString();
            result.intArray = new int[size];
            for (int i = 0; i < size; i++)
            {
                result.intArray[i] = rndGen.Next();
            }

            return result;
        }
    }
    [ServiceContract]
    public interface ITest
    {
        [WebGet(ResponseFormat = WebMessageFormat.Json)]
        MyDC GetLargeData(int size);
    }
    public class Service : ITest
    {
        public MyDC GetLargeData(int size)
        {
            return MyDC.CreateLargeInstance(size);
        }
    }

    #region Gzip Encoder Sample
    //This class is used to create the custom encoder (GZipMessageEncoder)
    internal class GZipMessageEncoderFactory : MessageEncoderFactory
    {
        MessageEncoder encoder;

        //The GZip encoder wraps an inner encoder
        //We require a factory to be passed in that will create this inner encoder
        public GZipMessageEncoderFactory(MessageEncoderFactory messageEncoderFactory)
        {
            if (messageEncoderFactory == null)
                throw new ArgumentNullException("messageEncoderFactory", "A valid message encoder factory must be passed to the GZipEncoder");
            encoder = new GZipMessageEncoder(messageEncoderFactory.Encoder);

        }

        //The service framework uses this property to obtain an encoder from this encoder factory
        public override MessageEncoder Encoder
        {
            get { return encoder; }
        }

        public override MessageVersion MessageVersion
        {
            get { return encoder.MessageVersion; }
        }

        //This is the actual GZip encoder
        class GZipMessageEncoder : MessageEncoder
        {
            static string GZipContentType = "application/x-gzip";

            //This implementation wraps an inner encoder that actually converts a WCF Message
            //into textual XML, binary XML or some other format. This implementation then compresses the results.
            //The opposite happens when reading messages.
            //This member stores this inner encoder.
            MessageEncoder innerEncoder;

            //We require an inner encoder to be supplied (see comment above)
            internal GZipMessageEncoder(MessageEncoder messageEncoder)
                : base()
            {
                if (messageEncoder == null)
                    throw new ArgumentNullException("messageEncoder", "A valid message encoder must be passed to the GZipEncoder");
                innerEncoder = messageEncoder;
            }

            //public override string CharSet
            //{
            //    get { return ""; }
            //}

            public override string ContentType
            {
                get { return GZipContentType; }
            }

            public override string MediaType
            {
                get { return GZipContentType; }
            }

            //SOAP version to use - we delegate to the inner encoder for this
            public override MessageVersion MessageVersion
            {
                get { return innerEncoder.MessageVersion; }
            }

            public override bool IsContentTypeSupported(string contentType)
            {
                return this.innerEncoder.IsContentTypeSupported(contentType);
            }

            //Helper method to compress an array of bytes
            static ArraySegment<byte> CompressBuffer(ArraySegment<byte> buffer, BufferManager bufferManager, int messageOffset)
            {
                MemoryStream memoryStream = new MemoryStream();
                memoryStream.Write(buffer.Array, 0, messageOffset);

                using (GZipStream gzStream = new GZipStream(memoryStream, CompressionMode.Compress, true))
                {
                    gzStream.Write(buffer.Array, messageOffset, buffer.Count);
                }


                byte[] compressedBytes = memoryStream.ToArray();
                byte[] bufferedBytes = bufferManager.TakeBuffer(compressedBytes.Length);

                Array.Copy(compressedBytes, 0, bufferedBytes, 0, compressedBytes.Length);

                bufferManager.ReturnBuffer(buffer.Array);
                ArraySegment<byte> byteArray = new ArraySegment<byte>(bufferedBytes, messageOffset, compressedBytes.Length - messageOffset);

                return byteArray;
            }

            //Helper method to decompress an array of bytes
            static ArraySegment<byte> DecompressBuffer(ArraySegment<byte> buffer, BufferManager bufferManager)
            {
                MemoryStream memoryStream = new MemoryStream(buffer.Array, buffer.Offset, buffer.Count - buffer.Offset);
                MemoryStream decompressedStream = new MemoryStream();
                int totalRead = 0;
                int blockSize = 1024;
                byte[] tempBuffer = bufferManager.TakeBuffer(blockSize);
                using (GZipStream gzStream = new GZipStream(memoryStream, CompressionMode.Decompress))
                {
                    while (true)
                    {
                        int bytesRead = gzStream.Read(tempBuffer, 0, blockSize);
                        if (bytesRead == 0)
                            break;
                        decompressedStream.Write(tempBuffer, 0, bytesRead);
                        totalRead += bytesRead;
                    }
                }
                bufferManager.ReturnBuffer(tempBuffer);

                byte[] decompressedBytes = decompressedStream.ToArray();
                byte[] bufferManagerBuffer = bufferManager.TakeBuffer(decompressedBytes.Length + buffer.Offset);
                Array.Copy(buffer.Array, 0, bufferManagerBuffer, 0, buffer.Offset);
                Array.Copy(decompressedBytes, 0, bufferManagerBuffer, buffer.Offset, decompressedBytes.Length);

                ArraySegment<byte> byteArray = new ArraySegment<byte>(bufferManagerBuffer, buffer.Offset, decompressedBytes.Length);
                bufferManager.ReturnBuffer(buffer.Array);

                return byteArray;
            }


            //One of the two main entry points into the encoder. Called by WCF to decode a buffered byte array into a Message.
            public override Message ReadMessage(ArraySegment<byte> buffer, BufferManager bufferManager, string contentType)
            {
                //Decompress the buffer
                ArraySegment<byte> decompressedBuffer = DecompressBuffer(buffer, bufferManager);
                //Use the inner encoder to decode the decompressed buffer
                Message returnMessage = innerEncoder.ReadMessage(decompressedBuffer, bufferManager);
                returnMessage.Properties.Encoder = this;
                return returnMessage;
            }

            //One of the two main entry points into the encoder. Called by WCF to encode a Message into a buffered byte array.
            public override ArraySegment<byte> WriteMessage(Message message, int maxMessageSize, BufferManager bufferManager, int messageOffset)
            {
                //Use the inner encoder to encode a Message into a buffered byte array
                ArraySegment<byte> buffer = innerEncoder.WriteMessage(message, maxMessageSize, bufferManager, messageOffset);
                //Compress the resulting byte array
                return CompressBuffer(buffer, bufferManager, messageOffset);
            }

            public override Message ReadMessage(System.IO.Stream stream, int maxSizeOfHeaders, string contentType)
            {
                GZipStream gzStream = new GZipStream(stream, CompressionMode.Decompress, true);
                return innerEncoder.ReadMessage(gzStream, maxSizeOfHeaders);
            }

            public override void WriteMessage(Message message, System.IO.Stream stream)
            {
                using (GZipStream gzStream = new GZipStream(stream, CompressionMode.Compress, true))
                {
                    innerEncoder.WriteMessage(message, gzStream);
                }

                // innerEncoder.WriteMessage(message, gzStream) depends on that it can flush data by flushing 
                // the stream passed in, but the implementation of GZipStream.Flush will not flush underlying
                // stream, so we need to flush here.
                stream.Flush();
            }
        }
    }
    // This is constants for GZip message encoding policy.
    static class GZipMessageEncodingPolicyConstants
    {
        public const string GZipEncodingName = "GZipEncoding";
        public const string GZipEncodingNamespace = "http://schemas.microsoft.com/ws/06/2004/mspolicy/netgzip1";
        public const string GZipEncodingPrefix = "gzip";
    }

    //This is the binding element that, when plugged into a custom binding, will enable the GZip encoder
    public sealed class GZipMessageEncodingBindingElement
                        : MessageEncodingBindingElement //BindingElement
                        , IPolicyExportExtension
    {

        //We will use an inner binding element to store information required for the inner encoder
        MessageEncodingBindingElement innerBindingElement;

        //By default, use the default text encoder as the inner encoder
        public GZipMessageEncodingBindingElement()
            : this(new TextMessageEncodingBindingElement()) { }

        public GZipMessageEncodingBindingElement(MessageEncodingBindingElement messageEncoderBindingElement)
        {
            this.innerBindingElement = messageEncoderBindingElement;
        }

        public MessageEncodingBindingElement InnerMessageEncodingBindingElement
        {
            get { return innerBindingElement; }
            set { innerBindingElement = value; }
        }

        //Main entry point into the encoder binding element. Called by WCF to get the factory that will create the
        //message encoder
        public override MessageEncoderFactory CreateMessageEncoderFactory()
        {
            return new GZipMessageEncoderFactory(innerBindingElement.CreateMessageEncoderFactory());
        }

        public override MessageVersion MessageVersion
        {
            get { return innerBindingElement.MessageVersion; }
            set { innerBindingElement.MessageVersion = value; }
        }

        public override BindingElement Clone()
        {
            return new GZipMessageEncodingBindingElement(this.innerBindingElement);
        }

        public override T GetProperty<T>(BindingContext context)
        {
            if (typeof(T) == typeof(XmlDictionaryReaderQuotas))
            {
                return innerBindingElement.GetProperty<T>(context);
            }
            else
            {
                return base.GetProperty<T>(context);
            }
        }

        public override IChannelFactory<TChannel> BuildChannelFactory<TChannel>(BindingContext context)
        {
            if (context == null)
                throw new ArgumentNullException("context");

            context.BindingParameters.Add(this);
            return context.BuildInnerChannelFactory<TChannel>();
        }

        public override IChannelListener<TChannel> BuildChannelListener<TChannel>(BindingContext context)
        {
            if (context == null)
                throw new ArgumentNullException("context");

            context.BindingParameters.Add(this);
            return context.BuildInnerChannelListener<TChannel>();
        }

        public override bool CanBuildChannelListener<TChannel>(BindingContext context)
        {
            if (context == null)
                throw new ArgumentNullException("context");

            context.BindingParameters.Add(this);
            return context.CanBuildInnerChannelListener<TChannel>();
        }

        void IPolicyExportExtension.ExportPolicy(MetadataExporter exporter, PolicyConversionContext policyContext)
        {
            if (policyContext == null)
            {
                throw new ArgumentNullException("policyContext");
            }
            XmlDocument document = new XmlDocument();
            policyContext.GetBindingAssertions().Add(document.CreateElement(
                GZipMessageEncodingPolicyConstants.GZipEncodingPrefix,
                GZipMessageEncodingPolicyConstants.GZipEncodingName,
                GZipMessageEncodingPolicyConstants.GZipEncodingNamespace));
        }
    }
    #endregion

    static Binding GetBinding()
    {
        CustomBinding custom = new CustomBinding(new WebHttpBinding());
        for (int i = 0; i < custom.Elements.Count; i++)
        {
            if (custom.Elements[i] is WebMessageEncodingBindingElement)
            {
                WebMessageEncodingBindingElement webBE = (WebMessageEncodingBindingElement)custom.Elements[i];
                custom.Elements[i] = new GZipMessageEncodingBindingElement(webBE);
                break;
            }
        }

        return custom;
    }

    class MyContentEncodingBehavior : IEndpointBehavior, IDispatchMessageInspector
    {
        public void AddBindingParameters(ServiceEndpoint endpoint, BindingParameterCollection bindingParameters)
        {
        }

        public void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime)
        {
        }

        public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
        {
            endpointDispatcher.DispatchRuntime.MessageInspectors.Add(this);
        }

        public void Validate(ServiceEndpoint endpoint)
        {
        }

        public object AfterReceiveRequest(ref Message request, IClientChannel channel, InstanceContext instanceContext)
        {
            return null;
        }

        public void BeforeSendReply(ref Message reply, object correlationState)
        {
            HttpResponseMessageProperty resp = (HttpResponseMessageProperty)reply.Properties[HttpResponseMessageProperty.Name];
            resp.Headers[HttpResponseHeader.ContentEncoding] = "gzip";
        }
    }

    public static void Test()
    {
        string baseAddress = "http://" + Environment.MachineName + ":8000/Service";
        ServiceHost host = new ServiceHost(typeof(Service), new Uri(baseAddress));
        var endpoint = host.AddServiceEndpoint(typeof(ITest), GetBinding(), "");
        endpoint.Behaviors.Add(new WebHttpBehavior());
        endpoint.Behaviors.Add(new MyContentEncodingBehavior());
        host.Open();
        Console.WriteLine("Host opened");

        HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(baseAddress + "/GetLargeData?size=1000");
        HttpWebResponse resp;
        try
        {
            resp = (HttpWebResponse)req.GetResponse();
        }
        catch (WebException ex)
        {
            resp = (HttpWebResponse)ex.Response;
        }

        Console.WriteLine("HTTP/{0} {1} {2}", resp.ProtocolVersion, (int)resp.StatusCode, resp.StatusDescription);
        foreach (var header in resp.Headers.AllKeys)
        {
            Console.WriteLine("{0}: {1}", header, resp.Headers[header]);
        }

        Console.Write("Press ENTER to close the host");
        Console.ReadLine();
        host.Close();
    }
}