rest - 如何访问 Servant 中的 http header ？

Question

我有一个带有 rest api 的简单服务应用程序:

type API = "items" :> Get '[JSON] [MyData]

app :: Application
app = serve api server

api :: Proxy API
api = Proxy

server :: Server API
server = getItems

getItems :: ExceptT ServantErr IO [MyData]
getItems = ......

startApp :: IO ()
startApp = run 1234 app

如何根据条件访问 http header 并返回特定响应，例如 http403？

Answer 1

使用 Servant 的 Header ( Servant Docs )

type API = "items" 
           :> Header "Auth-token" Text 
           :> Get '[JSON] [MyData]

然后

handler :: Maybe Text -> ExceptT ServantErr IO [MyData]
handler (Just "secret-code") = right [mydata]
handler _                    = left $ err403 { errBody = "no access" }