How to keep Rails from Processing Large XML Post

Question

In our rails application we have a many actions that do regular webapp actions. But, we have a single action that accepts a large XML file. I would like to keep rails from parsing the XML into params. Instead, I would like to be able to get the URL params ( /documents/{id}/action ) and then write out the xml file to a specific directory. How do I keep Rails from processing it?

How would I define the action to handle this?

def handle_xml
   # what to put here
end

The upload is done using Content-Type: application/xml It is a single file, and not part of a multipart form. The sample curl statement would be:

curl-H 'Accept: application/xml' -H 'Content-Type: application/xml' -X POST -d '<?xml version="1.0" encoding="UTF-8"?><test></test>' http://0.0.0.0:3000/controller/handle_xml

Answer 1

If you want to prevent rails from automatically parsing the XML data into a hash of parameters, you'll have to replace the ParamsParser middleware with your own custom version.

When a file is posted to rails, the ParamsParser middleware modifies the request parameters and turns it into a Hash if the data format is xml. You can find the details in the params_parser.rb file in rails.

Here's a RoR mailing list message similar to the question that you've asked

Unfortunately, as a new user I can't post any more links, but you should search google with "Sanitizing POST params with custom Rack middleware" for some more details on writing custom rack middleware.

Answer 2

I too have come across this problem recently. However mine is in an internal application where I have full control over both the Rails app and the clients connecting to it.

In my app the client POSTs a large XML data set to the Rails app. I wanted to process the XML document in a delayed job (resque). My workaround was to make the client use an alternate content-type. I used application/octet-stream. This prevents Rails from parsing the POST data. The data is available in request.raw_post.