Can a web service return a stream?

Question

I've been writing a little application that will let people upload & download files to me. I've added a web service to this applciation to provide the upload/download functionality that way but I'm not too sure on how well my implementation is going to cope with large files.

At the moment the definitions of the upload & download methods look like this (written using Apache CXF):

boolean uploadFile(@WebParam(name = "username") String username,
    @WebParam(name = "password") String password,
    @WebParam(name = "filename") String filename,
    @WebParam(name = "fileContents") byte[] fileContents)
    throws UploadException, LoginException;

byte[] downloadFile(@WebParam(name = "username") String username,
    @WebParam(name = "password") String password,
    @WebParam(name = "filename") String filename) throws DownloadException,
    LoginException;

So the file gets uploaded and downloaded as a byte array. But if I have a file of some stupid size (e.g. 1GB) surely this will try and put all that information into memory and crash my service.

So my question is - is it possible to return some kind of stream instead? I would imagine this isn't going to be terribly OS independent though. Although I know the theory behind web services, the practical side is something that I still need to pick up a bit of information on.

Cheers for any input, Lee

Answer 1

Yes, it is possible with Metro. See the Large Attachments example, which looks like it does what you want.

JAX-WS RI provides support for sending and receiving large attachments in a streaming fashion.

• Use MTOM and DataHandler in the programming model.
• Cast the DataHandler to StreamingDataHandler and use its methods.
• Make sure you call StreamingDataHandler.close() and also close the StreamingDataHandler.readOnce() stream.
• Enable HTTP chunking on the client-side.