Shell :

curl --digest 'http://monitor:monitor-123@localhost:9990/management' --header "Content-Type: application/json" -d '{"operation":"read-attribute","name":"server-state","json.pretty":1}'

Ruby :

#!/usr/bin/ruby
require 'rubygems'
require 'net/http'
require 'json'
require 'uri'
require 'net/http/digest_auth'

digest_auth = Net::HTTP::DigestAuth.new

url = URI.parse("http://localhost:9990/management")
url.user = 'monitor'
url.password = 'monitor-123'

payload = { "operation" => "read-attribute", "name" => "server-state", "json.pretty" => 1 }
pj=payload.to_json

http = Net::HTTP.new(url.host, url.port)

request = Net::HTTP::Get.new url.path

response = http.request request
# response is a 401 response with a WWW-Authenticate header

auth = digest_auth.auth_header url, response['www-authenticate'], 'POST'

# create a new request with the Authorization header
request = Net::HTTP::Post.new(url.path, initheader = {'Content-Type' =>'application/json'})
request.add_field 'Authorization', auth

# re-issue request with Authorization
request.body = pj
response=http.request(request)
puts response