### Dependency Injection { #dependency-injection }

FastAPI includes an extremely easy to use, but extremely powerful <abbr title='also known as "components", "resources", "services", "providers"'><strong>Dependency Injection</strong></abbr> system.

Es erreicht etwas Ähnliches wie Flask-apispec.

Es verfügt über ein integriertes Dependency Injection System, welches von Angular 2 inspiriert ist. Erfordert ein Vorab-Registrieren der „Injectables“ (wie alle anderen Dependency Injection Systeme, welche ich kenne), sodass der Code ausschweifender wird und es mehr Codeverdoppelung gibt.

        uses: actions/setup-python@v5
        with:
          python-version: "3.10"
          # Issue ref: https://github.com/actions/setup-python/issues/436
          # cache: "pip"
          # cache-dependency-path: pyproject.toml
      - name: Install build dependencies
        run: pip install build
      - name: Build distribution
        env:
          TIANGOLO_BUILD_PACKAGE: ${{ matrix.package }}

* Alle Schlüsselwort-Argumente, die an die Taskfunktion übergeben werden sollen (`message="some notification"`).

## Dependency Injection

We see that we are going to need some dependencies used in several places of the application.

So we put them in their own `dependencies` module (`app/dependencies.py`).

We will now use a simple dependency to read a custom `X-Token` header:

//// tab | Python 3.9+

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

////

 *
 * @since 4.0.0
 */
@Experimental
public enum CacheRetention {
    /**
     * Data should be persisted across Maven invocations.
     * Suitable for:
     * - Dependency resolution results
     * - Compilation outputs
     * - Downloaded artifacts
     */
    PERSISTENT,

    /**
     * Data should be retained for the duration of the current Maven session.
     * Suitable for:

                + " -Dversion=aVersion -Dclassifier=aClassifier -Dpackaging=jar -Dfile=/path/to/file"
                + " -Durl=[url] -DrepositoryId=[id]" + LS + LS + "  Path to dependency: " + LS + "  \t1) dependency1"
                + LS + "  \t2) dependency2" + LS + LS;
        String actual = AbstractArtifactResolutionException.constructMissingArtifactMessage(

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNull;

/**
 * Verifies scope of root project is preserved regardless of parent dependency management.
 *
 * @see <a href="https://issues.apache.org/jira/browse/MNG-2919">MNG-2919</a>
 */
@Deprecated
@SuppressWarnings("checkstyle:UnusedLocalVariable")

package org.apache.maven.api;

import org.apache.maven.api.annotations.Experimental;
import org.apache.maven.api.annotations.Nonnull;
import org.apache.maven.api.annotations.Nullable;

/**
 * Version constraint for dependency.
 * Constraint is either a range ("[1,2)") or recommended version ("1.0").
 *
 * {@code VersionConstraint} objects are created using the
 * {@linkplain org.apache.maven.api.services.VersionParser} service.
 *

  echo "For $AWS_REGION switching to user teamcityus access token"
  echo "##teamcity[setParameter name='env.DEVELOCITY_ACCESS_KEY' value='%ge.gradle.org.access.key.us%;%gbt-td.grdev.net.access.key%']"
fi

# READ-ONLY DEPENDENCY CACHE
if [ -d "/opt/gradle-cache" ]; then
  echo "##teamcity[setParameter name='env.GRADLE_RO_DEP_CACHE' value='/opt/gradle-cache']"
  echo "Setting READ_ONLY Gradle cache via env.GRADLE_RO_DEP_CACHE to use /opt/gradle-cache"