Instances of Accept represent mimetypes. They are used for matching against the Accept HTTP header of the request, and for setting the Content-Type header of the response

Example:

>>> import Network.HTTP.Media ((//), (/:))
>>> data HTML
>>> :{
instance Accept HTML where
   contentType _ = "text" // "html" /: ("charset", "utf-8")
:}

Instantiate this class to register a way of serializing a type based on the Accept header.

Example:

data MyContentType

instance Accept MyContentType where
   contentType _ = "example" // "prs.me.mine" /: ("charset", "utf-8")

instance Show a => MimeRender MyContentType where
   mimeRender _ val = pack ("This is MINE! " ++ show val)

type MyAPI = "path" :> Get '[MyContentType] Int

Instantiate this class to register a way of deserializing a type based on the request's Content-Type header.

>>> import Network.HTTP.Media hiding (Accept)
>>> import qualified Data.ByteString.Lazy.Char8 as BSC
>>> data MyContentType = MyContentType String

>>> :{
instance Accept MyContentType where
   contentType _ = "example" // "prs.me.mine" /: ("charset", "utf-8")
:}

>>> :{
instance Read a => MimeUnrender MyContentType a where
   mimeUnrender _ bs = case BSC.take 12 bs of
     "MyContentType" -> return . read . BSC.unpack $ BSC.drop 12 bs
     _ -> Left "didn't start with the magic incantation"
:}

>>> type MyAPI = "path" :> ReqBody '[MyContentType] Int :> Get '[JSON] Int

A type that can be converted from application/x-www-form-urlencoded, with the possibility of failure.

A type that can be converted to application/x-www-form-urlencoded

Like eitherDecode but allows all JSON values instead of just objects and arrays.

Will handle trailing whitespace, but not trailing junk. ie.

>>> eitherDecodeLenient "1 " :: Either String Int
Right 1

>>> eitherDecodeLenient "1 junk" :: Either String Int
Left "trailing junk after valid JSON: endOfInput"