Stream Flat-File IDOCs in SAP using the WCF Channel Model

Article
02/02/2021

The Microsoft BizTalk Adapter for mySAP Business Suite supports node-value streaming for the SendIdoc and ReceiveIdoc operations. These operations are used to send and receive flat-file (string) IDOCs to and from the adapter. In both of these operations, the data for the entire IDOC is contained in a string under a single node (<idocData>). For large IDOCs, streaming the IDOC data between the adapter and your code may save significant memory resources.

For background information about how the adapter supports streaming, see Streaming and the SAP Adapter. You should read this topic before proceeding.

The sections in this topic describe how to implement node-value streaming for the SendIdoc and ReceiveIdoc operations when you use the WCF channel model.

Streaming Outbound Flat-File IDOCs to the Adapter

The adapter supports node-value streaming on the request message for the SendIdoc operation.

To support node-value streaming on SendIdoc operations in the WCF channel model, you must:

Implement a System.ServiceModel.Channels.BodyWriter that is capable of streaming the IDOC data (performing node-value streaming on the IDOC data).
Create the System.ServiceModel.Message used to invoke the operation by supplying the message body with this BodyWriter using an appropriate overload of the Message.Create method.

Implementing a BodyWriter

The following example shows an implementation of a BodyWriter that performs node-value streaming.

/// <summary>  
/// This class overrides the OnWriteBodyContents function to do node-value streaming  
/// </summary>  
class StreamingBodyWriter : BodyWriter, IDisposable  
{  
    XmlReader m_reader = null;  
  
    int m_chunkSize;  
    /// <summary>  
    /// Initializes the body writer  
    /// </summary>  
    /// <param name="reader">Reader for input</param>  
    /// <param name="chunkSize">The chunksize in which the data is passed to adapter</param>  
    public StreamingBodyWriter(XmlReader reader, int chunkSize)  
        : base(false)  
    {  
        m_reader = reader;  
        if (chunkSize <= 0)  
            throw new ApplicationException("ChunkSize should be a positive value");  
        m_chunkSize = chunkSize;  
    }  
  
    protected override void OnWriteBodyContents(XmlDictionaryWriter writer)  
    {  
        if (m_reader == null)  
            throw new ApplicationException("Reader cannot be null");  
  
        while (m_reader.Read())  
        {  
            switch (m_reader.NodeType)  
            {  
                case XmlNodeType.Element:  
                    writer.WriteStartElement(m_reader.LocalName, m_reader.NamespaceURI);  
                    break;  
                case XmlNodeType.Text:  
                    #region Streaming Code  
                    char[] tempBuffer = new char[m_chunkSize];  
                    int length = 0;  
                    while ((length = m_reader.ReadValueChunk(tempBuffer, 0, m_chunkSize)) > 0)  
                    {  
                        writer.WriteString(new String(tempBuffer, 0, length));  
                    }  
                    #endregion  
                    break;  
                case XmlNodeType.EndElement:  
                    writer.WriteEndElement();  
                    break;  
            }  
        }  
  
    }  
  
    #region IDisposable Members  
  
    public void Dispose()  
    {  
        if (m_reader != null)  
        {  
            m_reader.Close();  
            m_reader = null;  
        }  
    }  
  
    #endregion  
}

Creating a Message by using a BodyWriter

The following example shows how to create a SendIdoc request message using the BodyWriter in the preceding example. The message data is read from a file.

XmlReader readerIn = XmlReader.Create ("sendidoc.xml");  
// StreamingBodyWrtier class is responsible for streaming  
StreamingBodyWriter stBW = new StreamingBodyWriter(readerIn, chunkSize);  
  
Message InputMsg = Message.CreateMessage(MessageVersion.Default,  
    "http://Microsoft.LobServices.SAP/2007/03/Idoc/SendIdoc",   
    stBW);

Streaming Inbound Flat-File IDOCs from the Adapter

You receive a flat-file IDOCs in the inbound ReceiveIdoc operation. The adapter supports node-value streaming on the request message for the ReceiveIdoc operation.

To support node-value streaming on ReceiveIdoc operations in the WCF channel model, you must:

Implement a System.Xml.XmlDictionaryWriter that is capable of streaming the IDOC data (performing node-value streaming on the IDOC data).
Consume the Message by invoking its WriteBodyContents method with this XmlDictionaryWriter.

Implementing an XmlDictionaryWriter

The following example shows an implementation of an XmlDictionaryWriter that performs node-value streaming.

using System;  
using System.Xml;  
using System.Text;  
  
class FileXmlWriter : XmlDictionaryWriter  
{  
    XmlTextWriter xts;  
  
    public FileXmlWriter(string file)  
    {  
        xts = new XmlTextWriter(file, Encoding.UTF8);  
    }  
  
    public override void WriteBase64(byte[] buffer, int index, int count)  
    {  
        xts.WriteBase64(buffer, index, count);  
    }  
  
    public override void WriteCData(string text)  
    {  
        xts.WriteCData(text);  
    }  
  
    public override void WriteCharEntity(char ch)  
    {  
        xts.WriteCharEntity(ch);  
    }  
  
    public override void WriteChars(char[] buffer, int index, int count)  
    {  
        xts.WriteChars(buffer, index, count);  
    }  
  
    public override void WriteComment(string text)  
    {  
        xts.WriteComment(text);  
    }  
  
    public override void WriteDocType(string name, string pubid, string sysid, string subset)  
    {  
        xts.WriteDocType(name, pubid, sysid, subset);  
    }  
  
    public override void WriteEndAttribute()  
    {  
        xts.WriteEndAttribute();  
    }  
  
    public override void WriteEndDocument()  
    {  
        xts.WriteEndDocument();  
    }  
  
    public override void WriteEndElement()  
    {  
        xts.WriteEndElement();  
    }  
  
    public override void WriteEntityRef(string name)  
    {  
        xts.WriteEntityRef(name);  
    }  
  
    public override void WriteFullEndElement()  
    {  
        xts.WriteFullEndElement();  
    }  
  
    public override void WriteProcessingInstruction(string name, string text)  
    {  
        xts.WriteProcessingInstruction(name, text);  
    }  
  
    public override void WriteRaw(string data)  
    {  
        xts.WriteRaw(data);  
    }  
  
    public override void WriteRaw(char[] buffer, int index, int count)  
    {  
        xts.WriteRaw(buffer, index, count);  
    }  
  
    public override void WriteStartAttribute(string prefix, string localName, string ns)  
    {  
        xts.WriteStartAttribute(prefix, localName, ns);  
    }  
  
    public override void WriteStartDocument(bool standalone)  
    {  
        xts.WriteStartDocument(standalone);  
    }  
  
    public override void WriteStartDocument()  
    {  
        xts.WriteStartDocument();  
    }  
  
    public override void WriteStartElement(string prefix, string localName, string ns)  
    {  
        xts.WriteStartElement(localName);  
    }  
  
    public override void WriteString(string text)  
    {  
        xts.WriteString(text);  
    }  
  
    public override void WriteSurrogateCharEntity(char lowChar, char highChar)  
    {  
        xts.WriteSurrogateCharEntity(lowChar, highChar);  
    }  
  
    public override void WriteWhitespace(string ws)  
    {  
        xts.WriteWhitespace(ws);  
    }  
  
    public override void Close()  
    {  
        xts.Close();  
    }  
  
    public override void Flush()  
    {  
        xts.Flush();  
    }  
  
    public override string LookupPrefix(string ns)  
    {  
        return xts.LookupPrefix(ns);  
    }  
  
    public override WriteState WriteState  
    {  
        get { return xts.WriteState; }  
    }  
  
}

Consuming a Message by Using an XmlDictionaryWriter

The following example shows how to consume a ReceiveIdoc request message using the FileXmlWriter implemented in the preceding example. (The FileWriter class was created by sub-classing XmlDictionaryWriter.) The example uses an IReplyChannel channel to receive the ReceiveIdoc operation. The details of the channel creation have been omitted. The ReceiveIdoc request message is written to a file.

// Receive the ReceiveIdoc request message from the adapter.  
RequestContext rc = channel.ReceiveRequest();  
Message inputMsg = rc.RequestMessage;  
  
// Stream the request message to received_idoc.xml using the custom XmlDictionaryWriter.  
FileXmlWriter fileXmlWriter = new FileXmlWriter("received_idoc.xml");  
inputMsg.WriteBodyContents(fileXmlWriter);  
fileXmlWriter.Flush();  
fileXmlWriter.Close();

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