# Advanced Middleware

In the main tutorial you read how to add [Custom Middleware](../tutorial/middleware.md){.internal-link target=_blank} to your application.

And then you also read how to handle [CORS with the `CORSMiddleware`](../tutorial/cors.md){.internal-link target=_blank}.

In this section we'll see how to use other middlewares.

## Adding ASGI middlewares

But FastAPI also supports using <a href="https://docs.python.org/3/library/dataclasses.html" class="external-link" target="_blank">`dataclasses`</a> the same way:

```Python hl_lines="1  7-12  19-20"
{!../../../docs_src/dataclasses/tutorial001.py!}
```

  drainDuration: 2s
  #
  # The mode used to redirect inbound connections to Envoy. This setting
  # has no effect on outbound traffic: iptables REDIRECT is always used for
  # outbound connections.
  # If "REDIRECT", use iptables REDIRECT to NAT and redirect to Envoy.
  # The "REDIRECT" mode loses source addresses during redirection.
  # If "TPROXY", use iptables TPROXY to redirect to Envoy.

    this.itemReporter = checkNotNull(itemReporter);
  }

  /**
   * Adds {@code equalityGroup} with objects that are supposed to be equal to each other and not
   * equal to any other equality groups added to this tester.
   *
   * <p>The {@code @Nullable} annotations on the {@code equalityGroup} parameter imply that the

/**
 * A sorted map which forwards all its method calls to another sorted map. Subclasses should
 * override one or more methods to modify the behavior of the backing sorted map as desired per the
 * <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p><b>Warning:</b> The methods of {@code ForwardingSortedMap} forward <i>indiscriminately</i> to

     *
     * @param plugin The plugin for which to create a realm, must not be {@code null}.
     * @param parent The parent realm for the new realm, may be {@code null}.
     * @param parentImports The packages/types to import from the parent realm, may be {@code null}.
     * @param foreignImports The packages/types to import from foreign realms, may be {@code null}.

     1. plugin goal execution in a child is usually simply appended (at end): you can't try to insert in the middle of pre-existing inherited executions,

     2. append happens at plugin level first, then goal level, independently from phases.
        This means for example that adding pluginA:goal2 to pre-existing (pluginA:goal1, pluginB:goal) will lead to (pluginA:goal1, pluginA:goal2, pluginB:goal)

     *
     * @param artifact         Artifact to be transformed.
     * @param remoteRepository the repository to deploy to
     * @param localRepository  the local repository
     */
    void transformForDeployment(
            Artifact artifact, ArtifactRepository remoteRepository, ArtifactRepository localRepository)
            throws ArtifactDeploymentException;

/**
 * This interface supplies the API for providing feedback to the user from the <code>Mojo</code>, using standard
 * <code>Maven</code> channels.<br>
 * There should be no big surprises here, although you may notice that the methods accept
 * <code>java.lang.CharSequence</code> rather than <code>java.lang.String</code>. This is provided mainly as a

 * <li>Information needed to find the artifact file in a repository including extension and classifier</li>
 * <li>Information on how to use the artifact as a dependency: whether to add it to the classpath, whether to load its
 * dependencies transitively</li>
 * </ul>
 *
 */
public interface ArtifactHandler {
    @Deprecated
    String ROLE = ArtifactHandler.class.getName();

    /**