http-common- Common types for HTTP clients and servers

Safe HaskellNone




Basic types used in HTTP communications. This modules is re-exported by both Network.Http.Client and Pipes.Http.Client, so if you're using either of those you don't need to explicitly import this module.



data Request Source

A description of the request that will be sent to the server. Note unlike other HTTP libraries, the request body is not a part of this object; that will be streamed out by you when actually sending the request with sendRequest.

Request has a useful Show instance that will output the request line and headers (as it will be sent over the wire but with the \r characters stripped) which can be handy for debugging.

Note that the actual Host: header is not set until the request is sent, so you will not see it in the Show instance (unless you call setHostname to override the value inherited from the Connection).

data ExpectMode Source



data RequestBuilder α Source

The RequestBuilder monad allows you to abuse do-notation to conveniently setup a Request object.

buildRequest :: RequestBuilder α -> IO RequestSource

Run a RequestBuilder, yielding a Request object you can use on the given connection.

     q <- buildRequest $ do
         http POST "/api/v1/messages"
         setContentType "application/json"
         setHostname "" 80
         setAccept "text/html"
         setHeader "X-WhoDoneIt" "The Butler"

Obviously it's up to you to later actually send JSON data.

http :: Method -> ByteString -> RequestBuilder ()Source

Begin constructing a Request, starting with the request line.

setHostname :: Hostname -> Port -> RequestBuilder ()Source

Set the [virtual] hostname for the request. In ordinary conditions you won't need to call this, as the Host: header is a required header in HTTP 1.1 and is set directly from the name of the server you connected to when calling openConnection.

setAccept :: ByteString -> RequestBuilder ()Source

Indicate the content type you are willing to receive in a reply from the server. For more complex Accept: headers, use setAccept'.

setAccept' :: [(ByteString, Float)] -> RequestBuilder ()Source

Indicate the content types you are willing to receive in a reply from the server in order of preference. A call of the form:

         setAccept' [("text/html", 1.0),
                     ("application/xml", 0.8),
                     ("*/*", 0)]

will result in an Accept: header value of text/html; q=1.0, application/xml; q=0.8, */*; q=0.0 as you would expect.

setAuthorizationBasic :: ByteString -> ByteString -> RequestBuilder ()Source

Set username and password credentials per the HTTP basic authentication method.

         setAuthorizationBasic "Aladdin" "open sesame"

will result in an Authorization: header value of Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==.

Basic authentication does not use a message digest function to encipher the password; the above string is only base-64 encoded and is thus plain-text visible to any observer on the wire and all caches and servers at the other end, making basic authentication completely insecure. A number of web services, however, use SSL to encrypt the connection that then use HTTP basic authentication to validate requests. Keep in mind in these cases the secret is still sent to the servers on the other side and passes in clear through all layers after the SSL termination. Do not use basic authentication to protect secure or user-originated privacy-sensitve information.

setContentType :: ContentType -> RequestBuilder ()Source

Set the MIME type corresponding to the body of the request you are sending. Defaults to "text/plain", so usually you need to set this if PUTting.

setContentLength :: Int64 -> RequestBuilder ()Source

Specify the length of the request body, in bytes.

RFC 2616 requires that we either send a Content-Length header or use Transfer-Encoding: chunked. If you know the exact size ahead of time, then call this function; the body content will still be streamed out by io-streams in more-or-less constant space.

This function is special: in a PUT or POST request, http-streams will assume chunked transfer-encoding unless you specify a content length here, in which case you need to ensure your body function writes precisely that many bytes.

setExpectContinue :: RequestBuilder ()Source

Specify that this request should set the expectation that the server needs to approve the request before you send it.

This function is special: in a PUT or POST request, http-streams will wait for the server to reply with an HTTP/1.1 100 Continue status before sending the entity body. This is handled internally; you will get the real response (be it successful 2xx, client error, 4xx, or server error 5xx) in receiveResponse. In theory, it should be 417 if the expectation failed.

Only bother with this if you know the service you're talking to requires clients to send an Expect: 100-continue header and will handle it properly. Most servers don't do any precondition checking, automatically send an intermediate 100 response, and then just read the body regardless, making this a bit of a no-op in most cases.

setHeader :: ByteString -> ByteString -> RequestBuilder ()Source

Set a generic header to be sent in the HTTP request. The other methods in the RequestBuilder API are expressed in terms of this function, but we recommend you use them where offered for their stronger types.


data Response Source

A description of the response received from the server. Note unlike other HTTP libraries, the response body is not a part of this object; that will be streamed in by you when calling receiveResponse.

Like Request, Response has a Show instance that will output the status line and response headers as they were received from the server.

data TransferEncoding Source



getStatusCode :: Response -> StatusCodeSource

Get the HTTP response status code.

getStatusMessage :: Response -> ByteStringSource

Get the HTTP response status message. Keep in mind that this is not normative; whereas getStatusCode values are authoritative.

getHeader :: Response -> ByteString -> Maybe ByteStringSource

Lookup a header in the response. HTTP header field names are case-insensitive, so you can specify the name to lookup however you like. If the header is not present Nothing will be returned.

     let n = case getHeader p "Content-Length" of
                Just x' -> read x' :: Int
                Nothing -> 0

which of course is essentially what goes on inside the client library when it receives a response from the server and has to figure out how many bytes to read.

There is a fair bit of complexity in some of the other HTTP response fields, so there are a number of specialized functions for reading those values where we've found them useful.

data Method Source

HTTP Methods, as per RFC 2616


data Headers Source

The map of headers in a Request or Response. Note that HTTP header field names are case insensitive, so if you call setHeader on a field that's already defined but with a different capitalization you will replace the existing value.


updateHeader :: Headers -> ByteString -> ByteString -> HeadersSource

Set a header field to the specified value. This will overwrite any existing value for the field. Remember that HTTP fields names are case insensitive!

removeHeader :: Headers -> ByteString -> HeadersSource

Remove a header from the map. If a field with that name is not present, then this will have no effect.

buildHeaders :: [(ByteString, ByteString)] -> HeadersSource

Given a list of field-name,field-value pairs, construct a Headers map.

retrieveHeaders :: Headers -> [(ByteString, ByteString)]Source

Get the headers as a field-name,field-value association list.

class HttpType τ whereSource

Accessors common to both the outbound and return sides of an HTTP connection.


getHeaders :: τ -> HeadersSource

Get the Headers from a Request or Response. Most people do not need this; for most cases you just need to get a header or two from the response, for which you can use getHeader. On the other hand, if you do need to poke around in the raw headers,

 import Network.Http.Types

will give you functions like lookupHeader and updateHeader to to work with.