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Transferring Large Files Between .Net & Java: Web Services Interoperability

It seems alot people have been experiencing problems uploading/downloading extremely large files via web services between a .Net web services client and a Java based web service. This note will hopefully put the matter to rest. The JAX-WS / Metro framework requires one to pass/return a Datahandler when accepting/returning streamed data. The problem is that when generating the stub code in Microsoft Visual Studio from the WSDL exported from the Java server, a byte[] array is returned in place of the Data Handler. The reason is that .NET does not know what a Java Datahandler is. When processing a very large file, say. 3 GB, your client will run out of memory. What we really want is for .Net to generate a Stream object in place of the byte array. To accomplish this, we need to employ some trickery. Say you have a class called ServerService and you want to upload a file, specifying the file name as the parameter. You would do this as follows:

  @MTOM(enabled = true, threshold = 512)    
  @StreamingAttachment(parseEagerly=true, memoryThreshold=4000000L)   
  public class ServerService {   
   public upload(@WebParam(name="fileStream")StreamBody stream) {   
     Datahandler dh = stream.getDataHandler();   
    // copy data from datahandler to file   

The constraint of the above is that the upload method using a stream may have only one parameter. One way around to specify the file name & other attributes in the Data itself. Simply write a FilterInputStream that reads and parses the first few lines. These lines are the attribute/name pairs that describe the data, i.e. filename, etc. When a linefeed is encountered the data itself begins. The below class is necessary to jinx .Net into creating a Stream object:

 @XmlType(name = "StreamBody", namespace = "http://schemas.microsoft.com/Message")  
 public class StreamBody {  
    * The data stream.  
   public DataHandler dataHandler;  
   public DataHandler getDataHandler() {  
     return dataHandler;  
   public void setDataHandler(DataHandler dataHandler) {  
     this.dataHandler = dataHandler;  

To enable mtom in your Java web services server, modify the sun-jaxws.xml with enable-mtom="true" as follows:


To enable streaming and MTOM on the .Net client, modify a file called app.config and add the parameters messageEncoding="Mtom" and transferMode="Streamed".

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