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From: Daniel Kulp <dkulp@apache.org>
To: users@cxf.apache.org
Subject: Re: When transfering an object with a DataHandler field,
 is it OK not to read from the InputStream?
Date: Fri, 8 Oct 2010 10:03:46 -0400
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Cc: Benson Margulies <bimargulies@gmail.com>,
 Jimi
 =?utf-8?q?Hulleg=C3=A5rd?= <jimi.hullegard@mogul.com>
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On Friday 08 October 2010 9:16:47 am Benson Margulies wrote:
> On the wire, that blob has to travel as a MIME part. And there might
> be several such MIME parts. Unless you traffic in interceptors, as far
> as I know, the entire content will be pulled into memory, unless it's
> very big, in which case it ends up in a temp file. CXF can't just
> leave the socket that the data is arriving on sitting there waiting
> for you to read the stream on the data handler.

Actually, if it's the last MIME part that was asked for (that's a key point=
),=20
it WILL stream right off the socket.   It won't get buffered.  If something=
=20
causes it to have to search for another mime part (like asking the attachme=
nt=20
collection it's size), then it would get buffered, but for a normal "single=
=20
attachment through JAXB or SWA" type case, it would stream.   Spent a lot o=
f=20
time getting that working correctly.  :-)

 > 2010/10/8 Jimi Hulleg=C3=A5rd <jimi.hullegard@mogul.com>:
> > I have set up a simple webservice for testing, where the object to
> > transfer contains a bunch of simple fields, and then a DataHandler for
> > some binary data (a Blob, actually). It works just fine, and some test
> > with large files (500MB) proved to me that it really works without
> > having the entire data in memory on the server or on the client.
> >=20
> > But then I realised that in most use cases, we will not need this binary
> > data, so on the client side we will not read from the InputStream of the
> > DataHandler. But can that cause any problem? Because when I think about
> > it I don't really know how CXF handles this DataHandler. Maybe it
> > assumes that the entire content of the DataHandler InputStream will be
> > sent, and that it keeps the connection open until the client has
> > finished reading, or until some timeout. Or maybe it assumes the
> > opposite, that it can close the connection after it has transfered the
> > "normal" data, and then open a new connection if the client starts to
> > read from the InputStream of the DataHandler.
> >=20
> > If it is something like the first scenario, that what can I do to
> > transfer this object the right way, without having to read the
> > InputStream? I can't find any information about this in the
> > documentation.

Really, with the way HTTP works, there isn't much you CAN do.   The best yo=
u=20
can do is grab the input stream and close it immediately.   We'll call the=
=20
close on the underlying http input stream.   What happens then I'm unsure o=
f.

It COULD do one of two things:
1) Keep reading till the end of the stream anyway so the connection can be =
re-
used with the Keep-Alive things.

2) Close the underlying socket which would result in a SocketClosed type=20
exception on the server side.  This would close the connection entirely so =
a=20
future connection would require a new socket and everything to be re-setup.


=2D-=20
Daniel Kulp
dkulp@apache.org
http://dankulp.com/blog