init(Req, State) -> {ok, Req, State} terminate(Reason, Req, State) -> ok %% optional Req :: cowboy_req:req() State :: any() Reason :: normal | {crash, error | exit | throw, any()}
cowboy_handler - Plain HTTP handlers
The cowboy_handler middleware executes the handler selected
by the router or any other preceding middleware.
This middleware takes the handler module and initial state
from the handler and handler_opts environment values,
respectively. On completion, it adds a result value to
the middleware environment, containing the return value
of the terminate/3 callback (if defined) and ok otherwise.
This module also defines a callback interface for handling HTTP requests.
Plain HTTP handlers implement the following interface:
init(Req, State) -> {ok, Req, State} terminate(Reason, Req, State) -> ok %% optional Req :: cowboy_req:req() State :: any() Reason :: normal | {crash, error | exit | throw, any()}
These two callbacks are common to all handlers.
Plain HTTP handlers do all their work in the init/2
callback. Returning ok terminates the handler. If no
response is sent, Cowboy will send a 204 No Content.
The optional terminate/3 callback will ultimately be called
with the reason for the termination of the handler.
Cowboy will terminate the process right after this. There
is no need to perform any cleanup in this callback.
The following terminate reasons are defined for plain HTTP handlers:
The connection was closed normally.
A crash occurred in the handler. Class and Reason can be
used to obtain more information about the crash. The function
erlang:get_stacktrace/0 can also be called to obtain the
stacktrace of the process when the crash occurred.
The following function should be called by modules implementing custom handlers to execute the optional terminate callback:
cowboy_handler:terminate(3) - Terminate the handler