* APIs externas
* sistemas de autenticación y autorización
* sistemas de monitoreo de uso de la API
* sistemas de inyección de datos de response
* etc.

## Simple y Poderoso { #simple-and-powerful }

Aunque el sistema de inyección de dependencias jerárquico es muy simple de definir y usar, sigue siendo muy poderoso.

Puedes definir dependencias que a su vez pueden definir dependencias ellas mismas.

    assert response.headers["WWW-Authenticate"] == 'Basic realm="simple"'


def test_security_http_basic_invalid_credentials():
    response = client.get(
        "/users/me", headers={"Authorization": "Basic notabase64token"}
    )
    assert response.status_code == 401, response.text
    assert response.headers["WWW-Authenticate"] == 'Basic realm="simple"'
    assert response.json() == {"detail": "Not authenticated"}

* external APIs
* authentication and authorization systems
* API usage monitoring systems
* response data injection systems
* etc.

## Simple and Powerful { #simple-and-powerful }

Although the hierarchical dependency injection system is very simple to define and use, it's still very powerful.

You can define dependencies that in turn can define dependencies themselves.

Apart from all the fancy words used here, the **Dependency Injection** system is quite simple.

Just functions that look the same as the *path operation functions*.

But still, it is very powerful, and allows you to declare arbitrarily deeply nested dependency "graphs" (trees).

/// tip

All this might not seem as useful with these simple examples.

But you will see how useful it is in the chapters about **security**.

  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>ut.simple</groupId>
  <artifactId>dependency</artifactId>
  <version>1.0</version>

  <name>Simple Unit Test Dependency</name>

* (Optionnellement) comprendre ce que vous, en tant que développeur, devez savoir sur HTTPS.
* Configurer un cluster en mode Docker Swarm avec HTTPS automatique, même sur un simple serveur à 5 dollars US/mois. En environ **20 min**.
* Générer et déployer une application **FastAPI** complète, en utilisant votre cluster Docker Swarm, avec HTTPS, etc. En environ **10 min**.

        <my.filter.value>hello</my.filter.value>
    </properties>

    <profiles>
        <profile>
            <id>two-conditions</id>
            <activation>
                <file>
                    <exists>simple.xml</exists>
                </file>
                <property>
                    <name>myproperty</name>
                    <value>test</value>
                </property>
            </activation>

     * @param simpleMessage
     *            Simple message with arguments expanded
     * @return Message with message code
     */
    public static String getFormattedMessage(final String messageCode, final String simpleMessage) {
        return "[" + messageCode + "]" + simpleMessage;
    }

    /**
     * Expands arguments and returns a simple message without a message code.
     *
     * @param messageCode

 * interfere with session-based authentication schemes that require cookies.
 *
 * As persistence, implementations of this interface must also provide storage of cookies. Simple
 * implementations may store cookies in memory; sophisticated ones may use the file system or
 * database to hold accepted cookies. The [cookie storage model][rfc_6265_53] specifies policies for
 * updating and expiring cookies.

    fields `username` and `password`.

    All the initialization parameters are extracted from the request.

    Read more about it in the
    [FastAPI docs for Simple OAuth2 with Password and Bearer](https://fastapi.tiangolo.com/tutorial/security/simple-oauth2/).

    ## Example

    ```python
    from typing import Annotated

    from fastapi import Depends, FastAPI