### Anwendungsfälle: Externer Service

Ein Beispiel könnte sein, dass Sie einen externen Authentifizierungsanbieter haben, mit dem Sie sich verbinden müssen.

Sie senden ihm ein Token und er gibt einen authentifizierten Benutzer zurück.

   * {@code null}!) before returning it to callers. Depending on how the code is structured, a
   * nullness analysis might not understand that the field has been populated. To avoid that problem
   * without having to add {@code @SuppressWarnings}, the code can call this method.
   *
   * <p>Why <i>not</i> just add {@code SuppressWarnings}? The problem is that this method is

   * {@code null}!) before returning it to callers. Depending on how the code is structured, a
   * nullness analysis might not understand that the field has been populated. To avoid that problem
   * without having to add {@code @SuppressWarnings}, the code can call this method.
   *
   * <p>Why <i>not</i> just add {@code SuppressWarnings}? The problem is that this method is

* `write(data)`: Записать данные `data` (`str` или `bytes`) в файл.
* `read(size)`: Прочитать количество `size` (`int`) байт/символов из файла.
* `seek(offset)`: Перейти к байту на позиции `offset` (`int`) в файле.
    * Наример, `await myfile.seek(0)` перейдет к началу файла.
    * Это особенно удобно, если вы один раз выполнили команду `await myfile.read()`, а затем вам нужно прочитать содержимое файла еще раз.

  /**
   * Invoked after a connection has been acquired for the `call`.
   *
   * This can be invoked more than 1 time for a single [Call]. For example, if the response
   * to the [Call.request] is a redirect to a different address.
   */
  open fun connectionAcquired(
    call: Call,
    connection: Connection,
  ) {
  }

  /**
   * Invoked after a connection has been released for the `call`.
   *

   *       expression involving {@code view} will throw)
   *   <li>{@code hashCode()} does not throw
   *   <li>if {@code node} is re-added to the graph after having been removed, {@code view}'s
   *       behavior is undefined
   * </ul>
   *
   * @throws IllegalArgumentException if {@code node} is not an element of this graph
   */
  @Override
  Set<N> adjacentNodes(N node);

werden können. <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers" class="external-link" target="_blank">Verwenden Sie dafür das Präfix 'X-'</a>.

Wenn Sie jedoch benutzerdefinierte Header haben, die ein Client in einem Browser sehen soll, müssen Sie sie zu Ihrer CORS-Konfigurationen ([CORS (Cross-Origin Resource Sharing)](cors.md){.internal-link target=_blank}) hinzufügen, indem Sie den Parameter `expose_headers` verwenden, der in der <a href="https://www.starlette.io/middlew...

	StateConnecting

	// StateConnected is the state when the connection has been established and is considered stable.
	// If the connection is lost, state will switch to StateConnecting.
	StateConnected

	// StateConnectionError is the state once a connection attempt has been made, and it failed.
	// The connection will remain in this stat until the connection has been successfully re-established.
	StateConnectionError

    validations:
      required: true

  - type: markdown
    attributes:
      value: >
        Did you *actually* encounter the need for this enhancement in a real-world scenario, or does
        it just seem like a sensible behavior for the feature to have?


        Before we make significant changes to existing features in Guava, we really want to be sure

        "The parameter is incorrect.", "Too many Uids active on this session.", "The Uid is not known as a valid user identifier on this session.",
        "The pipe has been ended.", "The filename, directory name, or volume label syntax is incorrect.", "The directory is not empty.",
        "Cannot create a file when that file already exists.", "All pipe instances are busy.", "The pipe is being closed.",