You're sending post data as a hash. You should encode it as string.
For example Using URI::encode_www_form
:
request = Net::HTTP::Post.new(uri)
...
response = nhttp.start do |http|
post_data = URI.encode_www_form({xml: xml})
http.request(request, post_data)
end
UPDATE If you want GET request, append the query string to the url.
post_data = URI.encode_www_form({xml: xml})
uri = URI('https://cig.dhl.de/services/sandbox/rest/sendungsverfolgung?' +
post_data)
...
response = nhttp.start do |http|
http.request(request)
end