From 1b863c350ba1f9b8ad1cb458df514ab0fe6bb127 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Lo=C3=AFc=20Hoguin?= Date: Mon, 11 Dec 2017 11:27:17 +0100 Subject: Add documentation for Cowboy 2.2 --- docs/en/cowboy/2.2/guide/req_body/index.html | 303 +++++++++++++++++++++++++++ 1 file changed, 303 insertions(+) create mode 100644 docs/en/cowboy/2.2/guide/req_body/index.html (limited to 'docs/en/cowboy/2.2/guide/req_body') diff --git a/docs/en/cowboy/2.2/guide/req_body/index.html b/docs/en/cowboy/2.2/guide/req_body/index.html new file mode 100644 index 00000000..268c62a1 --- /dev/null +++ b/docs/en/cowboy/2.2/guide/req_body/index.html @@ -0,0 +1,303 @@ + + + + + + + + + + + + Nine Nines: Reading the request body + + + + + + + + + + + + + + +
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Reading the request body

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The request body can be read using the Req object.

+

Cowboy will not attempt to read the body until requested. +You need to call the body reading functions in order to +retrieve it.

+

Cowboy will not cache the body, it is therefore only +possible to read it once.

+

You are not required to read it, however. If a body is +present and was not read, Cowboy will either cancel or +skip its download, depending on the protocol.

+

Cowboy provides functions for reading the body raw, +and read and parse form urlencoded or multipart bodies. +The latter is covered in its own chapter.

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+

Request body presence

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Not all requests come with a body. You can check for +the presence of a request body with this function:

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cowboy_req:has_body(Req).
+

It returns true if there is a body; false otherwise.

+

In practice, this function is rarely used. When the +method is POST, PUT or PATCH, the request body +is often required by the application, which should +just attempt to read it directly.

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Request body length

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You can obtain the length of the body:

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Length = cowboy_req:body_length(Req).
+

Note that the length may not be known in advance. In +that case undefined will be returned. This can happen +with HTTP/1.1’s chunked transfer-encoding, or HTTP/2 +when no content-length was provided.

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Cowboy will update the body length in the Req object +once the body has been read completely. A length will +always be returned when attempting to call this function +after reading the body completely.

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Reading the body

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You can read the entire body with one function call:

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{ok, Data, Req} = cowboy_req:read_body(Req0).
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Cowboy returns an ok tuple when the body has been +read fully.

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By default, Cowboy will attempt to read up to 8MB +of data, for up to 15 seconds. The call will return +once Cowboy has read at least 8MB of data, or at +the end of the 15 seconds period.

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These values can be customized. For example, to read +only up to 1MB for up to 5 seconds:

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{ok, Data, Req} = cowboy_req:read_body(Req0,
+    #{length => 1000000, period => 5000}).
+

You may also disable the length limit:

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{ok, Data, Req} = cowboy_req:read_body(Req0, #{length => infinity}).
+

This makes the function wait 15 seconds and return with +whatever arrived during that period. This is not +recommended for public facing applications.

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These two options can effectively be used to control +the rate of transmission of the request body.

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Streaming the body

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When the body is too large, the first call will return +a more tuple instead of ok. You can call the +function again to read more of the body, reading +it one chunk at a time.

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read_body_to_console(Req0) ->
+    case cowboy_req:read_body(Req0) of
+        {ok, Data, Req} ->
+            io:format("~s", [Data]),
+            Req;
+        {more, Data, Req} ->
+            io:format("~s", [Data]),
+            read_body_to_console(Req)
+    end.
+

The length and period options can also be used. +They need to be passed for every call.

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+

Reading a form urlencoded body

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+

Cowboy provides a convenient function for reading and +parsing bodies sent as application/x-www-form-urlencoded.

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{ok, KeyValues, Req} = cowboy_req:read_urlencoded_body(Req0).
+

This function returns a list of key/values, exactly like +the function cowboy_req:parse_qs/1.

+

The defaults for this function are different. Cowboy will +read for up to 64KB and up to 5 seconds. They can be modified:

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{ok, KeyValues, Req} = cowboy_req:read_urlencoded_body(Req0,
+    #{length => 4096, period => 3000}).
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+ Cowboy + 2.2 + + User Guide +

+ + + +

Navigation

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Version select

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