### Inyección de dependencias

FastAPI incluye un sistema de <abbr title='también conocido como "componentes", "recursos", "servicios", "proveedores"'><strong>Inyección de Dependencias</strong></abbr> extremadamente fácil de usar, pero extremadamente potente.

* Incluso las dependencias pueden tener dependencias, creando una jerarquía o **"gráfico de dependencias"**.
* Todo **manejado automáticamente** por el framework.

        // file reference. But this may be a Maven Plugin that we need to resolve from a remote repository
        // as well as its dependencies.

        if (request.isResolveRoot() /* && rootArtifact.getFile() == null */) {
            try {
                resolve(rootArtifact, request.getRemoteRepositories(), session);

    }

    private static String formatLocationInPom(Dependency dependency) {
        return "Dependency: " + ArtifactUtils.versionlessKey(dependency.getGroupId(), dependency.getArtifactId());
    }

    public Dependency getDependency() {
        return dependency;
    }

    public String getProjectId() {
        return projectId;
    }

    public File getPomFile() {
        return pomFile;
    }

Also fügen wir sie in ihr eigenes `dependencies`-Modul (`app/dependencies.py`) ein.

Wir werden nun eine einfache Abhängigkeit verwenden, um einen benutzerdefinierten `X-Token`-Header zu lesen:

//// tab | Python 3.9+

```Python hl_lines="3  6-8" title="app/dependencies.py"
{!> ../../docs_src/bigger_applications/app_an_py39/dependencies.py!}
```

////

//// tab | Python 3.8+

Мы поместим их в отдельный модуль `dependencies` (`app/dependencies.py`).

Теперь мы воспользуемся простой зависимостью, чтобы прочитать кастомизированный `X-Token` из заголовка:

//// tab | Python 3.9+

```Python hl_lines="3  6-8" title="app/dependencies.py"
{!> ../../docs_src/bigger_applications/app_an_py39/dependencies.py!}
```

////

//// tab | Python 3.8+

/**
 * Defines a hierarchical visitor for collecting dependency node trees.
 *
 * @since 4.0.0
 */
@Experimental
@Consumer
public interface NodeVisitor {
    /**
     * Starts the visit to the specified dependency node.
     *
     * @param node the dependency node to visit
     * @return <code>true</code> to visit the specified dependency node's children, <code>false</code> to skip the

    - tutorial/body-updates.md
    - Dependencies:
      - tutorial/dependencies/index.md
      - tutorial/dependencies/classes-as-dependencies.md
      - tutorial/dependencies/sub-dependencies.md
      - tutorial/dependencies/dependencies-in-path-operation-decorators.md
      - tutorial/dependencies/global-dependencies.md
      - tutorial/dependencies/dependencies-with-yield.md
    - Security:

            } catch (Exception e) {
                // Expected due to missing dependencies in test environment
                assertTrue(true);
                return;
            }

            assertEquals(0, functionBuilders.size());
        } catch (Exception e) {
            // Expected due to missing dependencies in test environment
            assertTrue(true);
        }
    }

 *  Upgrade: [AndroidX Startup 1.2.0][startup_1_2_0]. The Android variant of the `okhttp` artifact
    now depends on this. This is a new dependency.

 *  Upgrade: [AndroidX Annotation 1.9.1][annotation_1_9_1]. As above, the Android variant of the
    `okhttp` artifact now depends on this. This is also a new dependency.


## Version 5.0.0-alpha.14

_2024-04-17_

        return create(DependencyCoordinatesFactoryRequest.build(session, dependency));
    }

    @Nonnull
    default DependencyCoordinates create(@Nonnull Session session, Dependency dependency) {
        return create(DependencyCoordinatesFactoryRequest.build(
                session,
                dependency.getGroupId(),
                dependency.getArtifactId(),