How to POST XML content produced by a pipeline with HttpProxyGenerator?

[Luca Erzegovesi <lu...@economia.unitn.it>]

Hi. I am an end user, new to Cocoon. I am experimenting with 2.1m3.

First, let me spend a few words about the use case that originates my question.
I am developing a document management system for semi-structured data using XMLspy Authentic browser plugin as XML editor on the client side, and MS SQLserver as the document repository. Saving of documents is performed using updategrams, a technology embedded in MS SQLXML. Updategrams are files containing an XML representation of the Db records affected before and after the Db transaction, and rely on a schema which maps relational tables onto XML elements. Updategrams are translated into SQL INSERT, UPDATE and DELETE statements.
I started my project developing on the "nanonews" example provided on the XMLspy web site, where the server side processing is based on ASP pages. Soon afterwards I releazed that Cocoon would be a better platform to manage in an orderly way the flow of data to and from SQLserver, which involves a complex sequence of XSL transformations between the XML needed by the XML editor and the one loaded from or saved to the DB.

Getting to the point, I am happy to say that my attempts so far have been successful: I have managed to load the DB data into the XML editor, and also have been able to make a pipeline assembling a valid updategram. As a provisional solution, the updategram is saved it to a file and then is executed with a GET request.
Now I would like to take the final step, i.e. skipping the file save step and POSTing the updategram to an URl referencing the virtual directory of SQLXML.
I supposed that HttpProxyGenerator, which I found in the blocks section of 2.1m3 may be the right tool for the job, as it POSTs XML content passed as parameters to an URL (thanks to Pier Fumagalli for an <a href='http://marc.theaimsgroup.com/?l=xml-cocoon-dev&m=104491857707687&w=2'>informative message</a> on cocoon-dev list explaining its use, I had it working with no trouble) . Now, the XML I need to post is the output of a pipeline. How could it be assigned to the parameters of the HttpProxyGenerator?
I suppose that the most elegant solution would be a HttpProxyTransformer receiving the XML to post as input form the previous steps of the pipeline, but I am not ready for extending Cocoon components. Another solution may avail of the WriteSessionDOM transformer. Is there some other way to do that? 
Thanks for any advice.
Luca Erzegovesi
University of Trento