Network.HTTP.Simple

Simplified interface for common HTTP client interactions. Tutorial available at https://haskell-lang.org/library/http-client

Important note: Request is an instance of IsString, and therefore recommended usage is to turn on OverloadedStrings, e.g.

{-# LANGUAGE OverloadedStrings #-}
import Network.HTTP.Simple
import qualified Data.ByteString.Char8 as B8

main :: IO ()
main = httpBS "http://example.com" >>= B8.putStrLn . getResponseBody

The IsString instance uses parseRequest behind the scenes and inherits its behavior.

Perform requests

httpBS :: MonadIO m => Request -> m (Response ByteString)

Perform an HTTP request and return the body as a ByteString.

Since: 2.2.4

httpLBS :: MonadIO m => Request -> m (Response ByteString)

Perform an HTTP request and return the body as a lazy ByteString. Note that the entire value will be read into memory at once (no lazy I/O will be performed). The advantage of a lazy ByteString here (versus using httpBS) is--if needed--a better in-memory representation.

Since: 2.1.10

httpNoBody :: MonadIO m => Request -> m (Response ())

Perform an HTTP request and ignore the response body.

Since: 2.2.2

httpJSON :: (MonadIO m, FromJSON a) => Request -> m (Response a)

Perform an HTTP request and parse the body as JSON. In the event of an JSON parse errors, a JSONException runtime exception will be thrown.

Since: 2.1.10

httpJSONEither :: (MonadIO m, FromJSON a) => Request -> m (Response (Either JSONException a))

Perform an HTTP request and parse the body as JSON. In the event of an JSON parse errors, a Left value will be returned.

Since: 2.1.10

httpSink :: MonadUnliftIO m => Request -> (Response () -> ConduitM ByteString Void m a) -> m a

Perform an HTTP request and consume the body with the given Sink

Since: 2.1.10

httpSource :: (MonadResource m, MonadIO n) => Request -> (Response (ConduitM i ByteString n ()) -> ConduitM i o m r) -> ConduitM i o m r

Perform an HTTP request, and get the response body as a Source.

The second argument to this function tells us how to make the Source from the Response itself. This allows you to perform actions with the status or headers, for example, in addition to the raw bytes themselves. If you just care about the response body, you can use getResponseBody as the second argument here.

{-# LANGUAGE OverloadedStrings #-}
import           Control.Monad.IO.Class       (liftIO)
import           Control.Monad.Trans.Resource (runResourceT)
import           Data.Conduit                 (($$))
import qualified Data.Conduit.Binary          as CB
import qualified Data.Conduit.List            as CL
import           Network.HTTP.Simple
import           System.IO                    (stdout)

main :: IO ()
main =
    runResourceT
        $ httpSource "http://httpbin.org/robots.txt" getSrc
       $$ CB.sinkHandle stdout
  where
    getSrc res = do
        liftIO $ print (getResponseStatus res, getResponseHeaders res)
        getResponseBody res

Since: 2.2.1

withResponse :: (MonadUnliftIO m, MonadIO n) => Request -> (Response (ConduitM i ByteString n ()) -> m a) -> m a

Perform an action with the given request. This employes the bracket pattern.

This is similar to httpSource, but does not require MonadResource and allows the result to not contain a ConduitM value.

Since: 2.2.3

Types

type Query = [QueryItem]

Query.

General form: a=b&c=d, but if the value is Nothing, it becomes a&c=d.

data Request :: *

All information on how to connect to a host and what should be sent in the HTTP request.

If you simply wish to download from a URL, see parseRequest.

The constructor for this data type is not exposed. Instead, you should use either the defaultRequest value, or parseRequest to construct from a URL, and then use the records below to make modifications. This approach allows http-client to add configuration options without breaking backwards compatibility.

For example, to construct a POST request, you could do something like:

initReq <- parseRequest "http://www.example.com/path"
let req = initReq
            { method = "POST"
            }

For more information, please see http://www.yesodweb.com/book/settings-types.

Since 0.1.0

Instances

Show Request

Methods

showsPrec :: Int -> Request -> ShowS

show :: Request -> String

showList :: [Request] -> ShowS

data Response body :: * -> *

A simple representation of the HTTP response.

Since 0.1.0

Instances

Functor Response

Methods

fmap :: (a -> b) -> Response a -> Response b

(<$) :: a -> Response b -> Response a

Foldable Response

Methods

fold :: Monoid m => Response m -> m

foldMap :: Monoid m => (a -> m) -> Response a -> m

foldr :: (a -> b -> b) -> b -> Response a -> b

foldr' :: (a -> b -> b) -> b -> Response a -> b

foldl :: (b -> a -> b) -> b -> Response a -> b

foldl' :: (b -> a -> b) -> b -> Response a -> b

foldr1 :: (a -> a -> a) -> Response a -> a

foldl1 :: (a -> a -> a) -> Response a -> a

toList :: Response a -> [a]

null :: Response a -> Bool

length :: Response a -> Int

elem :: Eq a => a -> Response a -> Bool

maximum :: Ord a => Response a -> a

minimum :: Ord a => Response a -> a

sum :: Num a => Response a -> a

product :: Num a => Response a -> a

Traversable Response

Methods

traverse :: Applicative f => (a -> f b) -> Response a -> f (Response b)

sequenceA :: Applicative f => Response (f a) -> f (Response a)

mapM :: Monad m => (a -> m b) -> Response a -> m (Response b)

sequence :: Monad m => Response (m a) -> m (Response a)

Eq body => Eq (Response body)

Methods

(==) :: Response body -> Response body -> Bool

(/=) :: Response body -> Response body -> Bool

Show body => Show (Response body)

Methods

showsPrec :: Int -> Response body -> ShowS

show :: Response body -> String

showList :: [Response body] -> ShowS

data JSONException

An exception that can occur when parsing JSON

Since: 2.1.10

Constructors

JSONParseException Request (Response ()) ParseError

JSONConversionException Request (Response Value) String

Instances

Show JSONException

Methods

showsPrec :: Int -> JSONException -> ShowS

show :: JSONException -> String

showList :: [JSONException] -> ShowS

Exception JSONException

Methods

toException :: JSONException -> SomeException

fromException :: SomeException -> Maybe JSONException

displayException :: JSONException -> String

data HttpException :: *

An exception which may be generated by this library

Since: 0.5.0

Constructors

HttpExceptionRequest Request HttpExceptionContent

Most exceptions are specific to a Request. Inspect the HttpExceptionContent value for details on what occurred.

Since: 0.5.0

InvalidUrlException String String

A URL (first field) is invalid for a given reason (second argument).

Since: 0.5.0

Instances

Show HttpException

Methods

showsPrec :: Int -> HttpException -> ShowS

show :: HttpException -> String

showList :: [HttpException] -> ShowS

Exception HttpException

Methods

toException :: HttpException -> SomeException

fromException :: SomeException -> Maybe HttpException

displayException :: HttpException -> String

data Proxy :: *

Define a HTTP proxy, consisting of a hostname and port number.

Constructors

Proxy

Fields

• proxyHost :: ByteString

  The host name of the HTTP proxy.

• proxyPort :: Int

  The port number of the HTTP proxy.

Instances

Eq Proxy

Methods

(==) :: Proxy -> Proxy -> Bool

(/=) :: Proxy -> Proxy -> Bool

Ord Proxy

Methods

compare :: Proxy -> Proxy -> Ordering

(<) :: Proxy -> Proxy -> Bool

(<=) :: Proxy -> Proxy -> Bool

(>) :: Proxy -> Proxy -> Bool

(>=) :: Proxy -> Proxy -> Bool

max :: Proxy -> Proxy -> Proxy

min :: Proxy -> Proxy -> Proxy

Read Proxy

Methods

readsPrec :: Int -> ReadS Proxy

readList :: ReadS [Proxy]

readPrec :: ReadPrec Proxy

readListPrec :: ReadPrec [Proxy]

Show Proxy

Methods

showsPrec :: Int -> Proxy -> ShowS

show :: Proxy -> String

showList :: [Proxy] -> ShowS

Request constructions

defaultRequest :: Request

A default request value

Since: 0.4.30

parseRequest :: MonadThrow m => String -> m Request

Convert a URL into a Request.

This function defaults some of the values in Request, such as setting method to GET and requestHeaders to [].

Since this function uses MonadThrow, the return monad can be anything that is an instance of MonadThrow, such as IO or Maybe.

You can place the request method at the beginning of the URL separated by a space, e.g.:

@@ parseRequest "POST http://httpbin.org/post" @@

Note that the request method must be provided as all capital letters.

A Request created by this function won't cause exceptions on non-2XX response status codes.

To create a request which throws on non-2XX status codes, see parseUrlThrow

Since: 0.4.30

parseRequest_ :: String -> Request

Same as parseRequest, but in the cases of a parse error generates an impure exception. Mostly useful for static strings which are known to be correctly formatted.

Request lenses

Basics

setRequestMethod :: ByteString -> Request -> Request

Set the request method

Since: 2.1.10

setRequestSecure :: Bool -> Request -> Request

Set whether this is a secureHTTPS (True) or insecureHTTP (False) request

Since: 2.1.10

setRequestHost :: ByteString -> Request -> Request

Set the destination host of the request

Since: 2.1.10

setRequestPort :: Int -> Request -> Request

Set the destination port of the request

Since: 2.1.10

setRequestPath :: ByteString -> Request -> Request

Lens for the requested path info of the request

Since: 2.1.10

addRequestHeader :: HeaderName -> ByteString -> Request -> Request

Add a request header name/value combination

Since: 2.1.10

getRequestHeader :: HeaderName -> Request -> [ByteString]

Get all request header values for the given name

Since: 2.1.10

setRequestHeader :: HeaderName -> [ByteString] -> Request -> Request

Set the given request header to the given list of values. Removes any previously set header values with the same name.

Since: 2.1.10

setRequestHeaders :: [(HeaderName, ByteString)] -> Request -> Request

Set the request headers, wiping out all previously set headers. This means if you use setRequestHeaders to set some headers and also use one of the other setters that modifies the content-type header (such as setRequestBodyJSON), be sure that setRequestHeaders is evaluated first.

Since: 2.1.10

setRequestQueryString :: Query -> Request -> Request

Set the query string parameters

Since: 2.1.10

getRequestQueryString :: Request -> Query

Get the query string parameters

Since: 2.1.10

Request body

setRequestBody :: RequestBody -> Request -> Request

Set the request body to the given RequestBody. You may want to consider using one of the convenience functions in the modules, e.g. requestBodyJSON.

Note: This will not modify the request method. For that, please use requestMethod. You likely don't want the default of GET.

Since: 2.1.10

setRequestBodyJSON :: ToJSON a => a -> Request -> Request

Set the request body as a JSON value

Note: This will not modify the request method. For that, please use requestMethod. You likely don't want the default of GET.

This also sets the Content-Type to application/json; charset=utf-8

Since: 2.1.10

setRequestBodyLBS :: ByteString -> Request -> Request

Set the request body as a lazy ByteString

Note: This will not modify the request method. For that, please use requestMethod. You likely don't want the default of GET.

Since: 2.1.10

setRequestBodySource

Arguments

:: Int64

length of source

-> ConduitM () ByteString IO ()

-> Request

-> Request

Set the request body as a Source

Note: This will not modify the request method. For that, please use requestMethod. You likely don't want the default of GET.

Since: 2.1.10

setRequestBodyFile :: FilePath -> Request -> Request

Set the request body as a file

Note: This will not modify the request method. For that, please use requestMethod. You likely don't want the default of GET.

Since: 2.1.10

setRequestBodyURLEncoded :: [(ByteString, ByteString)] -> Request -> Request

Set the request body as URL encoded data

Note: This will change the request method to POST and set the content-type to application/x-www-form-urlencoded

Since: 2.1.10

Special fields

setRequestIgnoreStatus :: Request -> Request

Modify the request so that non-2XX status codes do not generate a runtime StatusCodeException.

Since: 0.4.29

setRequestBasicAuth

Arguments

:: ByteString

username

-> ByteString

password

-> Request

-> Request

Set basic auth with the given username and password

Since: 2.1.10

setRequestManager :: Manager -> Request -> Request

Instead of using the default global Manager, use the supplied Manager.

Since: 2.1.10

setRequestProxy :: Maybe Proxy -> Request -> Request

Override the default proxy server settings

Since: 2.1.10

Response lenses

getResponseStatus :: Response a -> Status

Get the status of the response

Since: 2.1.10

getResponseStatusCode :: Response a -> Int

Get the integral status code of the response

Since: 2.1.10

getResponseHeader :: HeaderName -> Response a -> [ByteString]

Get all response header values with the given name

Since: 2.1.10

getResponseHeaders :: Response a -> [(HeaderName, ByteString)]

Get all response headers

Since: 2.1.10

getResponseBody :: Response a -> a

Get the response body

Since: 2.1.10

Alternate spellings

httpLbs :: MonadIO m => Request -> m (Response ByteString)

Alternate spelling of httpLBS

Since: 2.1.10