http-enumerator-0.6.4.2: HTTP client package with enumerator interface and HTTPS support.

Network.HTTP.Enumerator

Contents

Description

This module contains everything you need to initiate HTTP connections. If you want a simple interface based on URLs, you can use simpleHttp. If you want raw power, http is the underlying workhorse of this package. Some examples: 

 -- Just download an HTML document and print it.
 import Network.HTTP.Enumerator
 import qualified Data.ByteString.Lazy as L

 main = simpleHttp "http://www.haskell.org/" >>= L.putStr

This example uses interleaved IO to write the response body to a file in constant memory space. By using httpRedirect, it will automatically follow 3xx redirects. 

 import Data.Enumerator
 import Data.Enumerator.Binary
 import Network.HTTP.Enumerator
 import System.IO
 
 main :: IO ()
 main = withFile "google.html" WriteMode $ \handle -> do
     request <- parseUrl "http://google.com/"
     withManager $ \manager -> do
         run_ $ httpRedirect request (\_ _ -> iterHandle handle) manager

The following headers are automatically set by this module, and should not be added to requestHeaders:

  • Content-Length
  • Host
  • Accept-Encoding (not currently set, but client usage of this variable will cause breakage).

Any network code on Windows requires some initialization, and the network library provides withSocketsDo to perform it. Therefore, proper usage of this library will always involve calling that function at some point. The best approach is to simply call them at the beginning of your main function, such as: 

 import Network.HTTP.Enumerator
 import qualified Data.ByteString.Lazy as L
 import Network (withSocketsDo)

 main = withSocketsDo
      $ simpleHttp "http://www.haskell.org/" >>= L.putStr

Synopsis

Perform a request

simpleHttp :: (MonadIO m, Failure HttpException m) => String -> m ByteStringSource

Download the specified URL, following any redirects, and return the response body.

This function will failure an HttpException for any response with a non-2xx status code. It uses parseUrl to parse the input. This function essentially wraps httpLbsRedirect.

Note: Even though this function returns a lazy bytestring, it does not utilize lazy I/O, and therefore the entire response body will live in memory. If you want constant memory usage, you'll need to write your own iteratee and use http or httpRedirect directly.

httpLbs :: MonadIO m => Request m -> Manager -> m ResponseSource

Download the specified Request, returning the results as a Response.

This is a simplified version of http for the common case where you simply want the response data as a simple datatype. If you want more power, such as interleaved actions on the response body during download, you'll need to use http directly. This function is defined as: 

httpLbs = http lbsIter

Please see lbsIter for more information on how the Response value is created.

Even though a Response contains a lazy bytestring, this function does not utilize lazy I/O, and therefore the entire response body will live in memory. If you want constant memory usage, you'll need to write your own iteratee and use http or httpRedirect directly.

httpLbsRedirect :: (MonadIO m, Failure HttpException m) => Request m -> Manager -> m ResponseSource

Download the specified Request, returning the results as a Response and automatically handling redirects.

This is a simplified version of httpRedirect for the common case where you simply want the response data as a simple datatype. If you want more power, such as interleaved actions on the response body during download, you'll need to use httpRedirect directly. This function is defined as: 

httpLbsRedirect = httpRedirect lbsIter

Please see lbsIter for more information on how the Response value is created.

Even though a Response contains a lazy bytestring, this function does not utilize lazy I/O, and therefore the entire response body will live in memory. If you want constant memory usage, you'll need to write your own iteratee and use http or httpRedirect directly.

http :: MonadIO m => Request m -> (Status -> ResponseHeaders -> Iteratee ByteString m a) -> Manager -> Iteratee ByteString m aSource

The most low-level function for initiating an HTTP request.

The first argument to this function gives a full specification on the request: the host to connect to, whether to use SSL, headers, etc. Please see Request for full details.

The second argument specifies how the response should be handled. It's a function that takes two arguments: the first is the HTTP status code of the response, and the second is a list of all response headers. This module exports lbsIter, which generates a Response value.

Note that this allows you to have fully interleaved IO actions during your HTTP download, making it possible to download very large responses in constant memory.

httpRedirect :: (MonadIO m, Failure HttpException m) => Request m -> (Status -> ResponseHeaders -> Iteratee ByteString m a) -> Manager -> Iteratee ByteString m aSource

Same as http, but follows all 3xx redirect status codes that contain a location header.

redirectIterSource

Arguments

:: (MonadIO m, Failure HttpException m) 
=> Int

number of redirects to attempt

-> Request m

Original request

-> (Status -> ResponseHeaders -> Iteratee ByteString m a) 
-> Manager 
-> Status -> ResponseHeaders -> Iteratee ByteString m a 

Make a request automatically follow 3xx redirects.

Used internally by httpRedirect and family.

Datatypes

data Request m Source

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 parseUrl.

Constructors

Request 

Fields

method :: Method

HTTP request method, eg GET, POST.

secure :: Bool

Whether to use HTTPS (ie, SSL).

checkCerts :: [X509] -> IO Bool

Check if the server certificate is valid. Only relevant for HTTPS.

host :: Ascii
 
port :: Int
 
path :: Ascii

Everything from the host to the query string.

queryString :: Query

Automatically escaped for your convenience.

requestHeaders :: RequestHeaders
 
requestBody :: RequestBody m
 

data RequestBody m Source

When using the RequestBodyEnum constructor and any function which calls redirectIter, you must ensure that the Enumerator can be called multiple times.

Constructors

RequestBodyLBS ByteString 
RequestBodyBS ByteString 
RequestBodyBuilder Int64 Builder 
RequestBodyEnum Int64 (Enumerator Builder m ()) 

data Response Source

A simple representation of the HTTP response created by lbsIter.

Constructors

Response 

Fields

statusCode :: Int
 
responseHeaders :: ResponseHeaders
 
responseBody :: ByteString
 

Instances

Manager

data Manager Source

Keeps track of open connections for keep-alive.

newManager :: IO ManagerSource

Create a new Manager with no open connection.

closeManager :: Manager -> IO ()Source

Close all connections in a Manager. Afterwards, the Manager can be reused if desired.

withManager :: MonadControlIO m => (Manager -> m a) -> m aSource

Create a new Manager, call the supplied function and then close it.

Utility functions

parseUrl :: Failure HttpException m => String -> m (Request m')Source

Convert a URL into a Request.

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

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

semiParseUrl :: Failure HttpException m => String -> m (Request m')Source

Same as parseUrl, with one distinction: this function will not attempt to parse the query string, but instead leave it with the path info. This can be useful if you need precise control of the rendering of the query string, such as using semicolons instead of ampersands.

lbsIter :: Monad m => Status -> ResponseHeaders -> Iteratee ByteString m ResponseSource

Convert the HTTP response into a Response value.

Even though a Response contains a lazy bytestring, this function does not utilize lazy I/O, and therefore the entire response body will live in memory. If you want constant memory usage, you'll need to write your own iteratee and use http or httpRedirect directly.

Request bodies

urlEncodedBody :: Monad m => [(ByteString, ByteString)] -> Request m' -> Request mSource

Add url-encoded paramters to the Request.

This sets a new requestBody, adds a content-type request header and changes the method to POST.

Exceptions

data HttpException Source

Constructors

StatusCodeException Int ByteString 
InvalidUrlException String String 
TooManyRedirects 
HttpParserException String 

Instances