Handling HTTP Query parameters in http-conduit - haskell

Question

I want to download the content of the URL
http://example.com/foobar?key1=value1&key2=value2
using http-conduit (GET request).
How can I do that:
a) Assuming I already know the full (i.e. encoded URL)
b) If some parameters are dynamic and therefore not URL-encoded?
Note: This question was answered Q&A-style and therefore intentionally does not show any research effort.

Answer 1

Regarding a):
You can use simpleHttp with an URL containing query parameters just like the example in the docs:
{-# LANGUAGE OverloadedStrings #-}
import Network.HTTP.Conduit
import qualified Data.ByteString.Lazy as LB
main :: IO ()
main =
simpleHttp "http://example.com/foobar?key1=value1&key2=value2" >>= LB.putStr
Regarding b):
You need a list of key/value tuples of type [(ByteString, Maybe ByteString)] that contains your query parameters.
{-# LANGUAGE OverloadedStrings #-}
import Network.HTTP.Conduit
import Data.ByteString (ByteString)
import qualified Data.ByteString.Lazy.Char8 as LB
queryParams :: [(ByteString, Maybe ByteString)]
queryParams = [
("key1", Just "value1"),
("key2", Just "value2")]
main :: IO ()
main = do
request <- parseUrl "http://example.com/foobar"
let request' = setQueryString queryParams request
response <- withManager $ httpLbs request'
LB.putStrLn $ responseBody response
Note: This requires at least http-conduit 2.1.
Also note that it is recommended to reuse Manager instances where applicable.