* or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *

# Middleware

You can add middleware to **FastAPI** applications.

A "middleware" is a function that works with every **request** before it is processed by any specific *path operation*. And also with every **response** before returning it.

* It takes each **request** that comes to your application.
* It can then do something to that **request** or run any needed code.

description: Report a problem about something that used to work
labels: [ "a:regression", "to-triage" ]
assignees: [ ]
body:
  - type: markdown
    attributes:
      value: |
        Please use our bug report template to report problems with something that has never worked.
        Regressions reports are greatly appreciated during our RC phase and before a final release.
  - type: textarea
    id: current-behavior
    attributes:
      label: Current Behavior

```

The TLS versions and cipher suites in each spec can change with each release. For example, in OkHttp 2.2 we dropped support for SSL 3.0 in response to the [POODLE](https://googleonlinesecurity.blogspot.ca/2014/10/this-poodle-bites-exploiting-ssl-30.html) attack. And in OkHttp 2.3 we dropped support for [RC4](https://en.wikipedia.org/wiki/RC4#Security). As with your desktop web browser, staying up-to-date with OkHttp is the best way to stay secure.

## An app with callbacks

Let's see all this with an example.

Imagine you develop an app that allows creating invoices.

These invoices will have an `id`, `title` (optional), `customer`, and `total`.

The user of your API (an external developer) will create an invoice in your API with a POST request.

Then your API will (let's imagine):

/*
 * Copyright (C) 2015 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,

	  # tags:
	  #   - key: "name"
	  #     value: "pick*" # match objects with tag 'name', with all values starting with 'pick'

	  ## NOTE: metadata filter not supported when "source" is non MinIO.
	  # metadata:
	  #   - key: "content-type"
	  #     value: "image/*" # match objects with 'content-type', with all values starting with 'image/'

	notify:

install ## ## In addition to default policies [readonly|readwrite|writeonly|consoleAdmin|diagnostics] ## you can define additional policies with custom supported actions and resources policies: [] ## writeexamplepolicy policy grants creation or deletion of buckets with name ## starting with example. In addition, grants objects write permissions on buckets starting with ## example. # - name: writeexamplepolicy # statements: # - resources: # - 'arn:aws:s3:::example*/*' # actions: # - "s3:AbortMultipartUpload"...

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