Happstack.Server.Routing

Route an incoming Request to a handler. For more in-depth documentation see this section of the Happstack Crash Course: http://happstack.com/docs/crashcourse/RouteFilters.html

Route by scheme

http :: (ServerMonad m, MonadPlus m) => m ()

guard which checks that an insecure connection was made via http://

Example:

 handler :: ServerPart Response
 handler =
     do https
        ...

https :: (ServerMonad m, MonadPlus m) => m ()

guard which checks that a secure connection was made via https://

Example:

 handler :: ServerPart Response
 handler =
     do https
        ...

Route by request method

methodM :: (ServerMonad m, MonadPlus m, MatchMethod method) => method -> m ()

Guard against the method. This function also guards against *any remaining path segments*. See method for the version that guards only by method.

Example:

 handler :: ServerPart Response
 handler =
     do methodM [GET, HEAD]
        ...

NOTE: This function is largely retained for backwards compatibility. The fact that implicitly calls nullDir is often forgotten and leads to confusion. It is probably better to just use method and call nullDir explicitly.

This function will likely be deprecated in the future.

methodOnly :: (ServerMonad m, MonadPlus m, MatchMethod method) => method -> m ()

Guard against the method only (as opposed to methodM).

Example:

 handler :: ServerPart Response
 handler =
     do methodOnly [GET, HEAD]
        ...

methodSP :: (ServerMonad m, MonadPlus m, MatchMethod method) => method -> m b -> m b

Guard against the method. Note, this function also guards against any remaining path segments. Similar to methodM but with a different type signature.

Example:

 handler :: ServerPart Response
 handler = methodSP [GET, HEAD] $ subHandler

NOTE: This style of combinator is going to be deprecated in the future. It is better to just use method.

 handler :: ServerPart Response
 handler = method [GET, HEAD] >> nullDir >> subHandler

method :: (ServerMonad m, MonadPlus m, MatchMethod method) => method -> m ()

Guard against the method only (as opposed to methodM).

Example:

 handler :: ServerPart Response
 handler =
     do methodOnly [GET, HEAD]
        ...

class MatchMethod m where

instances of this class provide a variety of ways to match on the Request method.

Examples:

 method GET                  -- match GET or HEAD
 method [GET, POST]          -- match GET, HEAD or POST
 method HEAD                 -- match HEAD /but not/ GET
 method (== GET)             -- match GET or HEAD
 method (not . (==) DELETE)  -- match any method except DELETE
 method ()                   -- match any method

As you can see, GET implies that HEAD should match as well. This is to make it harder to write an application that uses HTTP incorrectly. Happstack handles HEAD requests automatically, but we still need to make sure our handlers don't mismatch or a HEAD will result in a 404.

If you must, you can still do something like this to match GET without HEAD:

 guardRq ((== GET) . rqMethod)

Methods

matchMethod :: m -> Method -> Bool

Instances

MatchMethod ()

MatchMethod Method

MatchMethod [Method]

MatchMethod (Method -> Bool)

Route by pathInfo

dir :: (ServerMonad m, MonadPlus m) => String -> m a -> m a

Pop a path element and run the supplied handler if it matches the given string.

 handler :: ServerPart Response
 handler = dir "foo" $ dir "bar" $ subHandler

The path element can not contain '/'. See also dirs.

dirs :: (ServerMonad m, MonadPlus m) => FilePath -> m a -> m a

Guard against a FilePath. Unlike dir the FilePath may contain '/'. If the guard succeeds, the matched elements will be popped from the directory stack.

 dirs "foo/bar" $ ...

See also: dir.

nullDir :: (ServerMonad m, MonadPlus m) => m ()

guard which only succeeds if there are no remaining path segments

Often used if you want to explicitly assign a route for /

trailingSlash :: (ServerMonad m, MonadPlus m) => m ()

Guard which checks that the Request URI ends in '/'. Useful for distinguishing between foo and foo/

noTrailingSlash :: (ServerMonad m, MonadPlus m) => m ()

The opposite of trailingSlash.

anyPath :: (ServerMonad m, MonadPlus m) => m r -> m r

Pop any path element and run the handler.

Succeeds if a path component was popped. Fails is the remaining path was empty.

path :: (FromReqURI a, MonadPlus m, ServerMonad m) => (a -> m b) -> m b

Pop a path element and parse it using the fromReqURI in the FromReqURI class.

uriRest :: ServerMonad m => (String -> m a) -> m a

Grab the rest of the URL (dirs + query) and passes it to your handler.

Route by host

host :: (ServerMonad m, MonadPlus m) => String -> m a -> m a

Guard against the host.

This matches against the host header specified in the incoming Request.

Can be used to support virtual hosting, http://en.wikipedia.org/wiki/Virtual_hosting

see also: withHost

withHost :: (ServerMonad m, MonadPlus m) => (String -> m a) -> m a

Lookup the host header in the incoming request and pass it to the handler.

see also: host

Route by (Request -> Bool)

guardRq :: (ServerMonad m, MonadPlus m) => (Request -> Bool) -> m ()

Guard using an arbitrary function on the Request.