[undertow-dev] How to get response bytes before they are sent

[Stuart Douglas]

You need to buffer the whole response yourself, by default Undertow will just sent the bytes straight to the socket, so the headers will already be sent by the time the response is finished. 

You will need to write a StreamSinkConduit implementation that buffers the full response, then when terminateWrites() is called you sign the request using the buffered data, and then try and write out the buffered data. If it can't all be written out you finish writing it in the flush() method.

Stuart

----- Original Message -----
> From: "Vikas Nagaraj" <Vikas.Nagaraj at safenet-inc.com>
> To: undertow-dev at lists.jboss.org
> Sent: Thursday, 18 February, 2016 6:10:49 AM
> Subject: [undertow-dev] How to get response bytes before they are sent
> 
> Hello,
> Is it possible to get the full content of a response body before it’s sent?
> I’m trying to sign the response and add this signature in a header. There
> was a similar question on this list a couple of weeks ago, but that one was
> about signing the incoming request. My current approach is, in
> HttpHandler.handleRequest():
> - Create a javax.crypto.Signature object
> - Use HttpServerExchange. addResponseWrapper() to add a StreamSinkConduit
> that updates the Signature object as write() is called
> - Use HttpServerExchange.addResponseCommitListener() to add a callback that
> calls Signature.sign() when the response is ready to be sent
> Good in theory, but I’m finding that the sign happens before the updates –
> looks like the Conduit is only active as the response is being sent. Is
> there something else I should wrap to get the bytes as they’re being added
> to the response? Even better would be if I could read them directly from the
> ResponseCommitListener.beforeCommit() callback. I can see the number of
> bytes that have been written, but not the actual data.
> Note: I’m using Undertow 1.2.x, as we’re on WildFly 9.
> --
> Vikas Nagaraj
> vikas.nagaraj at safenet-inc.com
> 
> The information contained in this electronic mail transmission
> may be privileged and confidential, and therefore, protected
> from disclosure. If you have received this communication in
> error, please notify us immediately by replying to this
> message and deleting it from your computer without copying
> or disclosing it.
> 
> 
> _______________________________________________
> undertow-dev mailing list
> undertow-dev at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/undertow-dev