View Source Tesla.Middleware behaviour (tesla v1.11.2)
The middleware specification.
Middleware is an extension of basic Tesla
functionality. It is a module that must
implement Tesla.Middleware.call/3
.
Middleware options
Options can be passed to middleware in second param of Tesla.Builder.plug/2
macro:
plug Tesla.Middleware.BaseUrl, "https://example.com"
or inside tuple in case of dynamic middleware (Tesla.client/1
):
Tesla.client([{Tesla.Middleware.BaseUrl, "https://example.com"}])
Ordering
The order in which middleware is defined matters. Note that the order when sending the request matches the order the middleware was defined in, but the order when receiving the response is reversed.
For example, Tesla.Middleware.DecompressResponse
must come after Tesla.Middleware.JSON
,
otherwise the response isn't decompressed before it reaches the JSON parser.
Writing custom middleware
Writing custom middleware is as simple as creating a module implementing Tesla.Middleware.call/3
.
See Tesla.Middleware.call/3
for details.
Examples
defmodule MyProject.InspectHeadersMiddleware do
@behaviour Tesla.Middleware
@impl true
def call(env, next, _options) do
IO.inspect(env.headers)
with {:ok, env} <- Tesla.run(env, next) do
IO.inspect(env.headers)
{:ok, env}
end
end
end
Summary
Callbacks
Invoked when a request runs.
Callbacks
@callback call(env :: Tesla.Env.t(), next :: Tesla.Env.stack(), options :: any()) :: Tesla.Env.result()
Invoked when a request runs.
- (optionally) read and/or writes request data
- calls
Tesla.run/2
- (optionally) read and/or writes response data
Arguments
env
-Tesla.Env
struct that stores request/response datanext
- middlewares that should be called after current oneoptions
- middleware options provided by user