自定义消息编码器 C# 中的错误"Content-Type header from MTOM message not found"

Question

我有一个用c#编写的客户端应用程序，它需要使用用Java编写的第三方web服务，响应是MTOM。当我使用本机消息编码器并配置basicHttpBinding时，我收到了错误"字符集元素的内容长度…"。好吧，第三方服务(或web服务器容器)没有发送字符集，所以我决定创建一个自定义消息编码器和自定义绑定来捕获来自web服务器的响应，添加缺失的字符集并发送到应用层，但是当我处理我添加了字符集的消息时，我收到了一个错误"Content-Type header from MTOM message not found"。

这是我做的:

首先，我创建了一些类来处理message:
- CustomMtomBindingElementExtensionElement扩展BindingElementExtensionElement
- CustomMtomMessageEncodingBindingElement扩展MessageEncodingBindingElement和实现IWsdlExportExtension
- CustomMtomMessageEncoderFactory扩展MessageEncoderFactory
- CustomMtomMessageEncoder扩展MessageEncoder

在CustomMtomMessageEncoder中，我有一个私有属性，用于处理添加字符集后修改的消息:

public class CustomMtomMessageEncoder : MessageEncoder
{
    private MessageEncoder mtomEncoder;
    private CustomMtomMessageEncoderFactory factory;
    private XmlWriterSettings writerSettings;
    private string contentType;
    public CustomMtomMessageEncoder(CustomMtomMessageEncoderFactory factory)
    {
        this.factory = factory;
        this.writerSettings = new XmlWriterSettings();
        this.contentType = string.Format("{0}; charset={1}", this.factory.MediaType, this.writerSettings.Encoding.HeaderName);
        MtomMessageEncodingBindingElement mtomBindingElement = new MtomMessageEncodingBindingElement(this.MessageVersion, Encoding.GetEncoding(this.factory.CharSet));
        this.factory.ReaderQuotas.CopyTo(mtomBindingElement.ReaderQuotas);
        this.mtomEncoder = mtomBindingElement.CreateMessageEncoderFactory().Encoder;
    }
    //Other things...
}

在同一个类中，i重写ReadMessage方法:

    public override Message ReadMessage(ArraySegment<byte> buffer, BufferManager bufferManager, string contentType)
    {
        //Convert the received buffer into a string
        byte[] incomingResponse = buffer.Array;
        //read the first 500 bytes of the response
        string strFirst500 = System.Text.Encoding.UTF8.GetString(incomingResponse, 0, 500);
        //Check the last occurance of 'application/xop+xml' in the response. We check for the last
        //occurrence since the first one is present in the Content-Type HTTP Header. Once found,
        //append charset header to this string
        int appIndex = strFirst500.LastIndexOf("application/xop+xml");
        string modifiedResponse = strFirst500.Insert(appIndex + 19, "charset=utf-8");
        modifiedResponse = modifiedResponse.Replace("application/xop+xmlcharset=utf-8", "application/xop+xml; charset=utf-8");
        //convert the modified string back into a byte array
        byte[] ma = System.Text.Encoding.UTF8.GetBytes(modifiedResponse);
        //integrate the modified byte array back to the original byte array
        int increasedLength = ma.Length - 500;
        byte[] newArray = new byte[incomingResponse.Length + increasedLength];
        for (int count = 0; count < newArray.Length; count++)
        {
            if (count < ma.Length)
            {
                newArray[count] = ma[count];
            }
            else
            {
                newArray[count] = incomingResponse[count - increasedLength];
            }
        }
        //In this part generate a new ArraySegment<byte> buffer and pass it to the underlying MTOM Encoder.
        ArraySegment<byte> newBuffer = new ArraySegment<byte>(newArray);
        /*##### Here the error is triggered with message "can not create mtom reader for message" and inner exception is "Content-Type header from mtom message not found" #####*/
        Message mensagem = this.mtomEncoder.ReadMessage(newBuffer, bufferManager);
        return mensagem;
    }

错误发生在指示行"Message messagem = this.mtomEncoder"。ReadMessage (newBuffer bufferManager);"

请帮助。

谢谢,

卢西亚诺打破传统

Answer 1

解决这个问题的方法是在调用InnerEncoder.ReadMessage之前将内容类型(它是ReadMessage参数的一部分)附加到字节数组的开头。这是微软WCF不遵守SOAP标准。请注意，我正在使用VS2015。

const string ContentTypeHeader = "content-type";
var encoding = new UTF8Encoding(false);
var header = $"{ContentTypeHeader}: {headerValue}{Environment.NewLine}";
var headerBytes = encoding.GetBytes(header);
var contentWithHeader = new byte[headerBytes.Length + bytesToEncode.Length];
Buffer.BlockCopy(headerBytes, 0, contentWithHeader, 0, headerBytes.Length);
Buffer.BlockCopy(bytesToEncode, 0, contentWithHeader, headerBytes.Length, bytesToEncode.Length);
return contentWithHeader;

Answer 2

这个问题很老了，但我仍然想回答它，因为可能有更多的人在寻找答案:

您需要将contentType字符串传递给mtomEncoder。ReadMessage函数。

如果你在ReadMessage函数中改变了更多，你可能不得不在contentTypestring中改变同样的东西-但不要担心，你会收到一个干净的异常，这将帮助你解决你的问题。