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36 lines
1.4 KiB
Markdown
36 lines
1.4 KiB
Markdown
HTTP handlers
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=============
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Purpose
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-------
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HTTP handlers are the simplest Cowboy module to handle a request.
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Usage
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-----
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You need to implement three callbacks for HTTP handlers. The first,
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`init/3`, is common to all handlers. It receives three arguments:
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a tuple containing the transport and protocol in use, the `Req` object
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and the handler options you defined in the routes. In the context of
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HTTP handlers this should be used for any initialization needs. For
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example you can initialize here the `State` variable that will be
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passed to the following functions.
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The second callback, `handle/2`, is where most of your code should
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be. It receives two arguments: the `Req` object and the `State`
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previously defined. As the name explains, this is where you handle
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the request.
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The last callback, `terminate/3`, will be empty most of the time.
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It receives three arguments: the `Reason` for termination, the `Req`
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object and the `State` previously defined. This callback should be
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used strictly for cleaning up. Replying using the `Req` is disallowed.
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If you used the process dictionary, timers, monitors then you most
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likely want to stop them in this callback, as Cowboy might end up
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reusing this process for subsequent requests. Please see the
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Internals chapter for more information.
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Of course the general advice is to not use the process dictionary,
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and that any operation requiring reception of messages should be
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done in a loop handler, documented in its own chapter.
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