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It has been deprecated in OTP and the new way is available on all supported OTP versions.
67 lines
1.8 KiB
Text
67 lines
1.8 KiB
Text
= cowboy_handler(3)
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== Name
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cowboy_handler - Plain HTTP handlers
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== Description
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The `cowboy_handler` middleware executes the handler selected
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by the router or any other preceding middleware.
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This middleware takes the handler module and initial state
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from the `handler` and `handler_opts` environment values,
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respectively. On completion, it adds a `result` value to
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the middleware environment, containing the return value
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of the `terminate/3` callback (if defined) and `ok` otherwise.
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This module also defines a callback interface for handling
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HTTP requests.
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== Callbacks
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Plain HTTP handlers implement the following interface:
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[source,erlang]
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----
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init(Req, State) -> {ok, Req, State}
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terminate(Reason, Req, State) -> ok %% optional
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Req :: cowboy_req:req()
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State :: any()
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Reason :: normal
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| {crash, error | exit | throw, any()}
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----
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These two callbacks are common to all handlers.
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Plain HTTP handlers do all their work in the `init/2`
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callback. Returning `ok` terminates the handler. If no
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response is sent, Cowboy will send a `204 No Content`.
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The optional `terminate/3` callback will ultimately be called
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with the reason for the termination of the handler.
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Cowboy will terminate the process right after this. There
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is no need to perform any cleanup in this callback.
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The following terminate reasons are defined for plain HTTP
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handlers:
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normal::
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The connection was closed normally.
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{crash, Class, Reason}::
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A crash occurred in the handler. `Class` and `Reason` can be
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used to obtain more information about the crash.
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== Exports
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The following function should be called by modules implementing
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custom handlers to execute the optional terminate callback:
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* link:man:cowboy_handler:terminate(3)[cowboy_handler:terminate(3)] - Terminate the handler
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== See also
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link:man:cowboy(7)[cowboy(7)]
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