Re: Triggering download in GWT via RPC

The point I do not get about this is why the browser does not react to the content disposition by downloading the file and instead passing the response back to the ajax-world... <snip> ... I read a lot about that doing what i would like to do is not possible but no one really said why.

Browsers don't allow it because it is a major security issue. If it were possible, websites would start delivering malware using these mechanisms. Many people are stupid to just click okay. 

There is no way to automatically trigger a file download in a browser. File download can only begin when the user explicitly takes an action - such as clicking on a link.

--Sri

On 27 May 2010 19:47, andreas <horst.andreas82@googlemail.com> wrote:

Hi,

I'm trying to trigger a download via GWT rpc and/or GWT
RequestBuilder. The motivation of using rpc and/or RequestBuilder is
the ability to send data required for the on-the-fly generated
download files that way.

I already managed to modify the underlying request by using
RequestBuilder as return value of the rpc service method. The request
is routed to a HttpServlet implementing the doPost method. GWT utility
classes are used to obtain the RPCRequest instance and the given
parameters of the rpc service call successfully out of the
HttpRequest. After using the parameters and assembling the file on the
servlet in the doPost method the HttpResponse instance is used to
write that file. Headers 'content-disposition' and 'content-type' are
set accordingly to trigger a download in the browser.

However a download does not start. The response is accessible in the
RequestCallback instance assigned to the request. The point I do not
get about this is why the browser does not react to the content
disposition by downloading the file and instead passing the response
back to the ajax-world. I know that the rpc or request would fail
otherwise but that would be perfectly fine, since no response is
desired but a download.

Related posts:
http://groups.google.com/group/google-web-toolkit/browse_thread/thread/be6f95db3a4313c2/8f10a1c1e6500ccf?lnk=gst&q=download#8f10a1c1e6500ccf

http://groups.google.com/group/google-web-toolkit/browse_thread/thread/388e72fb8e652122/dea4693ce6642f2c?lnk=gst&q=download#dea4693ce6642f2c

I know that there are solutions with backposts and passing data via
parameters in the request url, but i would love to just stick to one
mechanism which is GWT rpc. I read a lot about that doing what i would
like to do is not possible but no one really said why. I especially
wonder why the browser does not do its thing since it is surely the
one that gets the response before the ajax code doesn't he?

I would like to hear about other solutions and if possible about why
exactly it is not possible to trigger download via GWT rpc. After all
escaping the GWT rpc mechanism on the server side works fine but on
the browser side not. Any ideas?

Greetings,
Andreas

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