wreq-0.2.0.0: An easy-to-use HTTP client library.

PortabilityGHC
Stabilityexperimental
Maintainerbos@serpentine.com
Safe HaskellNone

Network.Wreq.Lens

Contents

Description

HTTP client lens machinery.

When reading the examples in this module, you should assume the following environment:

 -- Make it easy to write literal ByteString and Text values.
 {-# LANGUAGE OverloadedStrings #-}

-- Our handy module.
 import Network.Wreq

-- Operators such as (&) and (.~).
 import Control.Lens

-- Conversion of Haskell values to JSON.
 import Data.Aeson (toJSON)

-- Easy traversal of JSON data.
 import Data.Aeson.Lens (key, nth)

Synopsis

Configuration

data Options Source

Options for configuring a client.

manager :: Lens' Options (Either ManagerSettings Manager)Source

A lens onto configuration of the connection manager provided by the http-client package.

In this example, we enable the use of OpenSSL for (hopefully) secure connections:

import OpenSSL.Session (context)
import Network.HTTP.Client.OpenSSL

let opts = defaults & manager .~ Left (opensslManagerSettings context)
withOpenSSL $
  getWith opts "https://httpbin.org/get"

proxy :: Lens' Options (Maybe Proxy)Source

A lens onto proxy configuration.

Example:

let opts = defaults & proxy .~ httpProxy "localhost" 8000
getWith opts "http://httpbin.org/get"

auth :: Lens' Options (Maybe Auth)Source

A lens onto request authentication.

Example (note the use of TLS):

let opts = defaults & auth .~ basicAuth "user" "pass"
getWith opts "https://httpbin.org/basic-auth/user/pass"

header :: HeaderName -> Lens' Options [ByteString]Source

A lens onto all headers with the given name (there can legitimately be zero or more).

Example:

let opts = defaults & header "Accept" .~ ["*/*"]
getWith opts "http://httpbin.org/get"

param :: Text -> Lens' Options [Text]Source

A lens onto all query parameters with the given name (there can legitimately be zero or more).

In this example, we construct the query URL "http://httpbin.org/get?foo=bar&foo=quux".

let opts = defaults & param "foo" .~ ["bar", "quux"]
getWith opts "http://httpbin.org/get"

redirects :: Lens' Options IntSource

A lens onto the maximum number of redirects that will be followed before an exception is thrown.

In this example, a HttpException will be thrown with a TooManyRedirects constructor, because the maximum number of redirects allowed will be exceeded.

let opts = defaults & redirects .~ 3
getWith opts "http://httpbin.org/redirect/5"

headers :: Lens' Options [Header]Source

A lens onto all headers (there can legitimately be zero or more).

In this example, we print all the headers sent by default with every request.

print (defaults ^. headers)

params :: Lens' Options [(Text, Text)]Source

A lens onto all query parameters.

cookie :: ByteString -> Traversal' Options CookieSource

A traversal onto the cookie with the given name, if one exists.

cookies :: Lens' Options CookieJarSource

A lens onto all cookies.

Proxy setup

data Proxy

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

proxyHost :: Lens' Proxy ByteStringSource

A lens onto the hostname portion of a proxy configuration.

proxyPort :: Lens' Proxy IntSource

A lens onto the TCP port number of a proxy configuration.

Cookie

cookieName :: Lens' Cookie ByteStringSource

A lens onto the name of a cookie.

cookieValue :: Lens' Cookie ByteStringSource

A lens onto the value of a cookie.

cookieExpiryTime :: Lens' Cookie UTCTimeSource

A lens onto the expiry time of a cookie.

cookieDomain :: Lens' Cookie ByteStringSource

A lens onto the domain of a cookie.

cookiePath :: Lens' Cookie ByteStringSource

A lens onto the path of a cookie.

cookieCreationTime :: Lens' Cookie UTCTimeSource

A lens onto the creation time of a cookie.

cookieLastAccessTime :: Lens' Cookie UTCTimeSource

A lens onto the last access time of a cookie.

cookiePersistent :: Lens' Cookie BoolSource

A lens onto whether a cookie is persistent across sessions (also known as a "tracking cookie").

cookieHostOnly :: Lens' Cookie BoolSource

A lens onto whether a cookie is host-only.

cookieSecureOnly :: Lens' Cookie BoolSource

A lens onto whether a cookie is secure-only, such that it will only be used over TLS.

cookieHttpOnly :: Lens' Cookie BoolSource

A lens onto whether a cookie is "HTTP-only".

Such cookies should be used only by browsers when transmitting HTTP requests. They must be unavailable in non-browser environments, such as when executing JavaScript scripts.

Response

data Response body

A simple representation of the HTTP response.

Since 0.1.0

responseBody :: Lens (Response body0) (Response body1) body0 body1Source

A lens onto the body of a response.

r <- get "http://httpbin.org/get"
print (r ^. responseBody)

responseHeaderSource

Arguments

:: HeaderName

Header name to match.

-> Traversal' (Response body) ByteString 

A lens onto all matching named headers in an HTTP response.

To access exactly one header (the result will be the empty string if there is no match), use the (^.) operator.

r <- get "http://httpbin.org/get"
print (r ^. responseHeader "Content-Type")

To access at most one header (the result will be Nothing if there is no match), use the (^?) operator.

r <- get "http://httpbin.org/get"
print (r ^? responseHeader "Content-Transfer-Encoding")

To access all (zero or more) matching headers, use the (^..) operator.

r <- get "http://httpbin.org/get"
print (r ^.. responseHeader "Set-Cookie")

responseLinkSource

Arguments

:: ByteString

Parameter name to match.

-> ByteString

Parameter value to match.

-> Fold (Response body) Link 

A fold over Link headers, matching on both parameter name and value.

For example, here is a Link header returned by the GitHub search API.

 Link:
   <https://api.github.com/search/code?q=addClass+user%3Amozilla&page=2>; rel="next",
   <https://api.github.com/search/code?q=addClass+user%3Amozilla&page=34>; rel="last"

And here is an example of how we can retrieve the URL for the next link programatically.

r <- get "https://api.github.com/search/code?q=addClass+user:mozilla"
print (r ^? responseLink "rel" "next" . linkURL)

responseCookieSource

Arguments

:: ByteString

Name of cookie to match.

-> Fold (Response body) Cookie 

A fold over any cookies that match the given name.

r <- get "http://www.nytimes.com/"
print (r ^? responseCookie "RMID")

responseHeaders :: Lens' (Response body) ResponseHeadersSource

A lens onto all headers in an HTTP response.

responseCookieJar :: Lens' (Response body) CookieJarSource

A lens onto all cookies set in the response.

responseStatus :: Lens' (Response body) StatusSource

A lens onto the status of an HTTP response.

responseVersion :: Lens' (Response body) HttpVersionSource

A lens onto the version of an HTTP response.

Status

data Status

HTTP Status.

Only the statusCode is used for comparisons.

Please use mkStatus to create status codes from code and message, or the Enum instance or the status code constants (like ok200). There might be additional record members in the future.

Note that the Show instance is only for debugging.

statusCode :: Lens' Status IntSource

A lens onto the numeric identifier of an HTTP status.

statusMessage :: Lens' Status ByteStringSource

A lens onto the textual description of an HTTP status.

Link header

data Link Source

An element of a Link header.

linkURL :: Lens' Link ByteStringSource

A lens onto the URL portion of a Link element.

linkParams :: Lens' Link [(ByteString, ByteString)]Source

A lens onto the parameters of a Link element.

POST body part

data Part

A single part of a multipart message.

partName :: Lens' Part TextSource

A lens onto the name of the input element associated with part of a multipart form upload.

partFileName :: Lens' Part (Maybe String)Source

A lens onto the filename associated with part of a multipart form upload.

partContentType :: Traversal' Part (Maybe MimeType)Source

A lens onto the content-type associated with part of a multipart form upload.

partGetBody :: Lens' Part (IO RequestBody)Source

A lens onto the code that fetches the data associated with part of a multipart form upload.

Parsing

atto :: Parser a -> Fold ByteString aSource

Turn an attoparsec Parser into a Fold.

Both headers and bodies can contain complicated data that we may need to parse.

Example: when responding to an OPTIONS request, a server may return the list of verbs it supports in any order, up to and including changing the order on every request (which httpbin.org /actually does/!). To deal with this possibility, we parse the list, then sort it.

>>> import Data.Attoparsec.ByteString.Char8 as A
>>> import Data.List (sort)
>>> 
>>> let comma = skipSpace >> "," >> skipSpace
>>> let verbs = A.takeWhile isAlpha_ascii `sepBy` comma
>>> 
>>> r <- options "http://httpbin.org/get"
>>> r ^. responseHeader "Allow" . atto verbs . to sort
["GET","HEAD","OPTIONS"]