cowboy_req(3)

Name

cowboy_req - HTTP request and response

Description

The module cowboy_req provides functions to access, manipulate and respond to requests.

There are four types of functions in this module. They can be differentiated by their name and their return type:

Any Req returned must be used in place of the one passed as argument. Functions that perform an action in particular write state in the Req object to make sure you are using the function correctly. For example, it's only possible to send one response, and to read the body once.

Exports

Raw request:

• cowboy_req:method(3) - HTTP method
• cowboy_req:version(3) - HTTP version
• cowboy_req:scheme(3) - URI scheme
• cowboy_req:host(3) - URI host name
• cowboy_req:port(3) - URI port number
• cowboy_req:path(3) - URI path
• cowboy_req:qs(3) - URI query string
• cowboy_req:uri(3) - Reconstructed URI
• cowboy_req:header(3) - HTTP header
• cowboy_req:headers(3) - HTTP headers
• cowboy_req:peer(3) - Peer address and port

Processed request:

• cowboy_req:parse_qs(3) - Parse the query string
• cowboy_req:match_qs(3) - Match the query string against constraints
• cowboy_req:parse_header(3) - Parse the given HTTP header
• cowboy_req:parse_cookies(3) - Parse cookie headers
• cowboy_req:match_cookies(3) - Match cookies against constraints
• cowboy_req:binding(3) - Access a value bound from the route
• cowboy_req:bindings(3) - Access all values bound from the route
• cowboy_req:host_info(3) - Access the route's heading host segments
• cowboy_req:path_info(3) - Access the route's trailing path segments

Request body:

• cowboy_req:has_body(3) - Is there a request body?
• cowboy_req:body_length(3) - Body length
• cowboy_req:read_body(3) - Read the request body
• cowboy_req:read_urlencoded_body(3) - Read and parse a urlencoded request body
• cowboy_req:read_part(3) - Read the next multipart headers
• cowboy_req:read_part_body(3) - Read the current part's body

Response:

• cowboy_req:set_resp_cookie(3) - Set a cookie
• cowboy_req:set_resp_header(3) - Set a response header
• cowboy_req:set_resp_headers(3) - Set several response headers
• cowboy_req:has_resp_header(3) - Is the given response header set?
• cowboy_req:resp_header(3) - Response header
• cowboy_req:resp_headers(3) - Response headers
• cowboy_req:delete_resp_header(3) - Delete a response header
• cowboy_req:set_resp_body(3) - Set the response body
• cowboy_req:has_resp_body(3) - Is there a response body?
• cowboy_req:reply(3) - Send the response
• cowboy_req:stream_reply(3) - Send the response headers
• cowboy_req:stream_body(3) - Stream the response body
• cowboy_req:push(3) - Push a resource to the client

Types

push_opts()

push_opts() :: #{
    method => binary(),            %% case sensitive
    scheme => binary(),            %% lowercase; case insensitive
    host   => binary(),            %% lowercase; case insensitive
    port   => inet:port_number(),
    qs     => binary()             %% case sensitive
}

Push options.

By default, Cowboy will use the GET method, an empty query string, and take the scheme, host and port directly from the current request's URI.

read_body_opts()

read_body_opts() :: #{
    length  => non_neg_integer(),
    period  => non_neg_integer(),
    timeout => timeout()
}

Body reading options.

The defaults are function-specific.

req()

req() :: #{
    method  := binary(),               %% case sensitive
    version := cowboy:http_version() | atom(),
    scheme  := binary(),               %% lowercase; case insensitive
    host    := binary(),               %% lowercase; case insensitive
    port    := inet:port_number(),
    path    := binary(),               %% case sensitive
    qs      := binary(),               %% case sensitive
    headers := cowboy:http_headers(),
    peer    := {inet:ip_address(), inet:port_number()}
}

The Req object.

Contains information about the request and response. While some fields are publicly documented, others aren't and shouldn't be used.

You may add custom fields if required. Make sure to namespace them by prepending an underscore and the name of your application:

Req#{_myapp_auth_method => pubkey}.

resp_body()

resp_body() :: iodata()
    | {sendfile, Offset, Length, Filename}

Offset   :: non_neg_integer()
Length   :: non_neg_integer()
Filename :: file:name_all()

Response body.

It can take two forms: the actual data to be sent or a tuple indicating which file to send.

When sending data directly, the type is either a binary or an iolist. Iolists are an efficient way to build output. Instead of concatenating strings or binaries, you can simply build a list containing the fragments you want to send in the order they should be sent:

1> RespBody = ["Hello ", [<<"world">>, $!]].
["Hello ",[<<"world">>,33]]
2> io:format("~s~n", [RespBody]).
Hello world!

Note that the length must be greater than zero for any data to be sent. Cowboy will send an empty body when the length is zero.

See also

cowboy(7)