[](https://hex.pm/packages/cowmachine)
# Cowmachine
Webmachine for Zotonic and Cowboy
This is an adaptation of https://github.com/webmachine/webmachine for the Cowboy web server.
Cowmachine is a request handler for Cowboy.
Main differences with Basho’s Webmachine are:
* Use cowboy instead of mochiweb for the http server
* Separate dispatching
* Simplified callbacks
* Single `process/4` callback for all http methods
* Caching of some callbacks (like `modified`)
* More streaming options for returned data
* Better support for range requests
## Installation
Cowmachine is at Hex, in your `rebar.config` file use:
```erlang
{deps, [
cowmachine
]}.
```
You can also use the direct Git url and use the development version:
```erlang
{deps, [
{cowmachine, {git, "https://github.com/zotonic/cowmachine.git", {branch, "master"}}}
]}.
```
## Calling Cowmachine
Cowmachine can be called from your Cowboy middleware:
```erlang
-spec execute(Req, Env) -> {ok, Req, Env} | {stop, Req}
when Req::cowboy_req:req(), Env::cowboy_middleware:env().
execute(Req, Env) ->
% Replace below with your own controller module and optionally wrap
% the request in your own request-context record or map.
EnvController = Env#{
cowmachine_controller => mycontroller
},
RequestContext = cowmachine_req:init_context(Req, EnvController, #{}),
% Set options for the cowmachine
Options = #{
on_welformed =>
fun(Ctx) ->
% Perform anything after well-formedness check of your request
% Examples are parsing the query args, or authentication
Ctx
end,
on_handled =>
fun(Ctx) ->
% Perform anything after processing, before sending the result.
Ctx
end
},
% Handle the request, returns updated Req and Env for next Cowboy middleware
cowmachine:request(RequestContext, Options).
```
Or just use the default Cowmachine middleware:
```erlang
#{
middlewares => [
% ... add your dispatcher middlware
cowmachine
],
request_timeout => 60000,
env => #{
% If no dispatcher, default to `mycontroller` as the cowmachine
% controller.
cowmachine_controller => mycontroller
}
}.
```
## Dispatching
You can use the [Zotonic Dispatch Compiler](https://github.com/zotonic/dispatch_compiler) to match your controller paths against the request.
## Controller
The controller provides the callbacks to handle the request.
The controller is an Erlang module implementing callback functions, only functions that return some non-default value need to be implemented.
For the controller callbacks and more documentation, check the [wiki pages](https://github.com/zotonic/cowmachine/wiki).
